February 2002 Forecast Outlook, Discussion & Report Page
|28||.||Discussion: A large,
slow moving high in the western Bight region is starting to weaken very slightly as it
progresses east. The trough in New South Wales continues to move northwards, triggering
showers & storms, particularly to its east and along the coastal fringe. The ITCZ is
edging equatorwards and currently lies close to the tropical coastline. The WA
trough is aligned along the west coast & looks to move off the coast during Thursday
as the monsoon low continues its westward drift.
Future Developments: The high in the Bight will ridge slowly eastwards over the next few days before reaching the Tasman Sea early in the week. The baric ridge will shift slightly northwards to lie over Victoria. The front moving through NSW will move into the northeast corner during Thursday. The area of convective activity in the eastern Coral Sea is moving southeast with decreasing central pressure. Ridging along the coast will block the eastwards movement of the inland Queensland trough & it may then move westwards for the next day or so triggering showers & storms along the troughline as well as in the moister air to its east.
The monsoon low in Western Australia looks to finally make ocean-fall over the next day or so. The high in the Bight will direct an SE-E surface flow onto the southern WA & SA coasts. The large area of moisture which originated from this low in has moved east and southeast during Tuesday and Wednesday & should continue to progress across the southeast of the continent under the influence of the subtropical jet during Thursday, which should see the cloud reach as far south as the Victorian ranges. The interaction between the front moving through the Bight & this rather large band of tropical moisture may also trigger showers & storms. A series of fronts will pass over Tasmania during the next couple of days.
Potential Risks: Possible light falls of snow on the Tasmanian highlands may be triggered as a series of fronts moves east. Keep an eye on the continuing development in the areas around Suva & also northeast of Papua-New Guinea.
|27||Clyve Herbert||Although not appearing in any forecast or outlook that's not a bad upper cloud band (baroclinic mid and upper levels) presently sneaking up on the northwest of Victoria, emanating from the remains of moisture outflow from WA .|
|27||Clyve Herbert||An interesting out of season tropical disturbance at 150east and about 8 degrees north is looking interesting this morning drifting west at the tip of a mid lat upper trough, also the chocolate freckle looking tropical low near Vila is still edging southward towards New Caledonia though appears to show limited surface convergence - upper divergence seems ok.|
|27||.||Discussion: The monsoon
low in the Pilbara region of Western Australia is maintaining its identity. Heat low in
western Queensland extends a trough to the southeast corner of the state and the NE of New
South Wales. The high, which is moving across New Zealand, extends a ridge along the
Queensland coast. As series of fronts is crossing Tasmania but will not affect the
mainland states to any great degree. The ITCZ extends from northern Cape York to the
monsoon low in Western Australia. An interesting area of low pressure remains in the
eastern Coral Sea & should be monitored.
Future Developments: The ridge of high pressure extending through the Bight will initially strengthen, then weaken slowly as it moves east through Bass Strait. The trough through southern New South Wales will move northeast triggering occasional storms with its passage. Increasing levels of moisture from Western Australia are being drawn into the trough which lies from the west of Queensland to the southeast corner & triggering storms along its length This Queensland trough is expected to remain quasi-stationery for the next day or so.
The WA heat trough will reform off the coast during Wednesday while the monsoon low edges ever closer to the Indian Ocean.This system is injecting large amounts of moisture into the area between 20S & 30S which will be transported east over the next few days. A series of weak fronts will pass through Tasmania during the remainder of the week bringing wind shifts towards cooler SW with passing showers.
Potential Risks: The monsoon low affecting much of central Western Australia may trigger widespread rain with occasional heavy falls in the Pilbara which may extend towards the SE of the state during Wednesday & Thursday. A large area of strong convection to the NE of Papua - New Guinea is worth keeping an eye on for further development over the next 24-36 hours.
Some of you may have watched a remarkable lightning show north of Melbourne last night between 2100hrs and 2300hrs, this storm/storms were producing at times between 40 and 60 lightning discharges per minute (peak between 2130 and 2230). Julian Hollis from Trentham reports that a location near Mt Alexander (south of Bendigo) recorded 68mm in just over half an hour around the above times last night, with fences washed away and some stock loss. The lightning was so frequent that the domed overshoot was clearly visible. A further phone call from Julian Hollis in respect to the lightning type associated with this Mt Alexander storm was the appearance of "sprites" extending upwards from the CB top on at least two occasions.
A look at the radar provided by Robert Goler shows some interesting behaviour in respect to motion of the Mt Alexander storm which showed apparent "developmental stalling" in the vicinity of Mt Alexander and also a possible left movement for a short time, however another storm on radar east of Cohuna at an earlier stage shows what appears to be a very pronounced left moving bias while another storm developing to its south moves off to the right ,although this second development seems associated with possible outflow from the storm near Cohuna.
Also in another part of the world there is a convective area north of New Caledonia with two centres this area looks somewhat interesting .
|26||.||Discussion: The high is
moving across the Tasman Sea towards New Zealand and the ridge along the Queensland coast
will weaken slightly. An upper level trough remains over NSW. A surface trough
extends from central west Queensland through northern New South Wales and continues to
interact with the moisture from the monsoon low & is triggering storms some of
which are rather large especially in Western Australia. The ITCZ extends from the top of
Cape York to the low in the Pilbara which extends a trough down the west coast. The band
of tropical moisture that originated 2 weeks ago with the monsoon low, continues to be a
major feature of the Australian latitudes. A large high is ridging into the western Bight.
A series of fronts is embedded in the westerly flow south of the Bight. Colder air
following the front is apparent in the southern Bight.
Future Developments: The trough through southern parts of eastern Australia will continue to move eastwards. The weak trough currently through Queensland from the central west to the southern interior will remain almost stationary through much of the week triggering isolated storms . The low over the Pilbara, which is moving very slowly west along the ITCZ, is expected to weaken, but is currently showing signs of restrengthening(?) both at the surface & in the middle levels. The high ridging into the Bight will strengthen for the next day or two bringing a S-SE onshore flow to South Australia and southern parts of Western Australia. The front moving through Tasmania & the southern part of Victoria will swing the winds around to the SW during Tuesday moderating temperatures particularly south of the ranges.
Potential Risks: The redevelopment of the low over the ocean to the west of Western Australia may again increase shower & storm activity.
|25||Rod Aikman (Bendigo)||Some details of the storm in the Mt Alexander area between 21:30 and 22:00 25th February are starting to come in. The biggest impact of the storm appears to have been on the eastern flank of Mt Alexander with a report of 70 mm of rain falling in 45 minutes at Sutton Grange (about 20 - 25 km away from here directly). There are reports of vehicle damage caused by hail, wind damage to buildings, and fences being washed away by flash flooding in the Sutton Grange area. There is a report of hail being the size of a 10 cent coin. From Bendigo the storm looked spectacular, with lightning discharges occurring within 1-2 seconds of each other.|
pressure ridges through Bass Strait into the Tasman Sea. A trough extends from
western Queensland through New South Wales to the southeast of the continent. The ITCZ
extends from Cape York, through the southern part of the Top End to the monsoon low, the
circulation of which is still evident in the Kimberley / Pilbara region of Western
Australia. The WA heat trough has moved inland from the coast & a front is approaching
the SW corner of Western Australia and is followed by another high ridging into the Bight
during Tuesday. A tropical low is evident in the far eastern Coral Sea. There
is a broad region of moist air being carried across the continent from WA by the
Future Developments: The trough through New South Wales will deepen and move westward as Tasmania splits the band of high pressure and the ridge along the east coast strengthens. The trough extending south into Victoria will become absorbed into the major trough moving into the southeast of the continent during the next couple of days. The formation of an upper level low during in west / central Queensland may trigger some heavy falls. Moisture will continue to move east & south east from the area around the monsoon low in Western Australia for the next few days, increasing the risk of shower & storm activity over much of central & eastern Australia. Seasonal storm activity will increase across northern Australia with the weakening of the monsoon trough.
Conditions in Western Australia will remain hot on the eastern side of the trough with slightly milder temperatures following its passage. Fine & hot conditions in southern parts of South Australia will moderate as a milder onshore airstream develops west of the trough with the approach of the next high, while the northern part of the state is expected to remain cloudy & showery.
Potential Risks: The area southwest of Suva continues to show strong possibility for TC development. There is a risk that an upper disturbance may develop over South Australia midweek.
|24||.||Discussion: The baric
ridge lying through Bass Strait to a high in the Tasman Sea is sending a strengthening
ridge along the Queensland coast. A surface trough is located through NSW. The ITCZ
extends from Cape York through to the Pilbara and there has been a weakening of the
monsoon trough. A broad band of moisture currently extends from the monsoon low
remaining over NW Western Australia, through central Australia to the northern part of NSW
& southern Queensland. The heat trough down the west coast of WA is deepening and will
move slowly inland Sunday & early in the week.
Future Developments: The trough over NSW will move slowly west during Sunday as the high strengthens in the Tasman. The ridge along the Queensland coast is expected to strengthen & the trough will move west triggering scattered showers and storms in the west of the state through Sunday. Seasonal storm activity will continue across the tropics with the weakening of the monsoon trough. The band of tropical moisture extending from Western Australia will continue expanding east & southeast over the next day or so in response to the upper jet. A weak front will pass to the south of WA during Sunday. Temperatures will moderate west of the heat trough early next week as it moves east. Temperatures through South Australia, Victoria and Tasmania will increase as the winds swing around to the NE.
Potential Risks: The development of an upper level low during Sunday / Monday in west / central Queensland during the early part of the week may trigger some heavy falls. An increase in available moisture over much of northern Western Australia & into the southern part of the Northern Territory & northern part of South Australia should be monitored as it expands southeast & east over the next couple of days. The strongly convective area northwest of Suva is continuing to show signs of improved organisation & should be watched.
|23||Clyve Herbert||What a remarkable occurrence to see the two tropical disturbances go poof!, the large monsoonal low over northwest WA has laid itself bare showing a skeleton of low cloud spiral bands with the upper cloud all but disappeared! the same thing has happened to the tropical low over open ocean west of Broome, not a bad trick! I have to say I haven't seen that to often, or are they just taking a breather?|
|23||Nick Sykes||I'm thinking Monday looks better in Melb now with what looks like a middle level trough moving through, 500mb temps are expected to be around -14. The problem with Monday is there wont be as much time for moisture to move down from the north. Tuesday doesn't look so good, but depends a lot on the timing of the change. If like last Wednesday the change is delayed to the afternoon Melbourne may see some action. I'm more inclined to think it will push east, with NE Vic the go.|
Strengthening high in the Bight extends a ridge eastwards through northern Victoria. The
rather more northerly-than-usual position of this ridge over land for this time of year is
a result of the influence of the deep low currently south of Tasmania. As the low
moves away, the baric ridge will edge back south to lie through Bass Strait. The trough
marked by the outflow cloudband from the NW continues to move NE. The convergence area
over the Gulf of Carpentaria is expanding and moving slowly west along the ITCZ. The
monsoon low over the Kimberley region of Western Australia continues to exhibit a
'tropical cyclone' signature over land. The WA heat trough continues to deepen off
the west coast and will move slowly east over the next few days. Temperatures over
WA will continue to rise east of the trough.
Future Developments: The baric ridge will strengthen during the next couple of days and then shift south over the weekend to lie through Bass Strait. The high in the Bight will position itself over the SE of Australia during the weekend. A trough developing southwards through inland NSW late Saturday, early Sunday will extend into NE Victoria with possible storms. Showers & storms are expected to become more widespread through inland South Australia (!!) under the influence of the monsoon low &its moist outflow.
Potential Risks The monsoon low over the Kimberley continues edging towards the Indian Ocean & is maintaining its 'TC' signature. Possible sleet on the higher parts of Tasmania Thursday night. Possible storms in South Australia!
|21||Clyve Herbert||Our monsoonal low over the Kimberley is looking better all the time and is still edging westward ever closer to the open ocean, this system has fantastic upper support with strong divergence and a large south-eastward outflow feeding into the 'black hole' low south of Tasmania. If this 'atmospheric process' gets over the sea there is as strong possibility of a significant TC so keep looking. The area over the southeast Gulf of Carpentaria is also showing some activity with weak to moderate low to mid convergence but very limited upper outflow divergence, the area north of Fiji continues to be very convectively positive with a huge area of cloud which is also interacting with an upper mid latitude long wave trough.|
|21||.||Discussion: The deep low
in the south of the Bight will continue moving south of Tasmania & a front will move
north along the coast of NSW. The trough over inland NSW is interacting with
moisture which originated from the NW tropics, and showers & storms over inland NSW
will contract as the cloudband moves NE during Thursday. Clearing conditions in the
SW. The high near New Zealand will reinforce the ridge along the Queensland coast
maintaining a SE flow onto the coast. The monsoon low in the north will continue to move
westwards. Conditions in the NT will remain cloudy throughout with rain areas and storms
& scattered heavy falls, mainly over the Top End. The WA heat trough is beginning to
reform along the west coast, while a high strengthens through the northern Bight directing
easterlies across the southern part of the state. Temperatures in southern WA will rise
towards the weekend.
Future Developments: The high in the Bight will maintain a SW flow over southeastern Australia during the next day or so. Showers will be more frequent across Tasmania & the coastal fringes of SA & Victoria, while north of the ranges in Victoria should remain mostly fine. A series of deep lows will pass through the south of the Bight over the next few days while the high will ridge through Bass Strait.
Potential Risks The monsoon low currently moving westwards along the ITCZ is beginning to develop a 'tropical low' signature & should be monitored as it approaches the Indian Ocean. There is a very small risk that a wave low may develop off the far south coast of NSW or east of Tasmania early Thursday.
|20||Clyve Herbert||The cold front is into western Victoria at the moment (0800hrs) in a line running from west of Mildura to just near Cape Otway, dew points are rather high in the northeast of the state and only moderate ahead of the front through central areas, looks as if at this stage higher moisture levels wont interact with this front until it reaches the east of Vic later today. There are some interesting obs here in Geelong though, surface winds are from about 360 to 010 15 to 25 knots temp 25c, bar 1002hpa, although the lower winds are rather strong the mid levels are remarkable slow with only very slow movement of the Alto cumulus from a bearing of about 320 to 330 degrees.|
|20||.||Discussion: A deep low
(965hPa at 4pm AEDST) is situated in the southern Bight. A ridge of high pressure extends
along the Queensland coast from the high in the Tasman. Pressures over the north of
Australia remain low and the ITCZ extends from tropical Queensland, through the Tennant
Creek area to the Pilbara in Western Australia with the area of lowest pressure continuing
to move westward along the ITCZ. The strengthening jet over South Australia will
capture tropical moisture from the NW and feed it into the trough which is moving into SE
Australia. The west-east temperature gradient in the mid levels (850hPa) is steepening as
the system progresses east. A strong thermal trough trails the surface front.
Future Developments: The trough continues to deepen as it approaches Victoria. Showers and scattered storms are likely to develop along its length as it progresses east. Temperatures will increase in inland NSW ahead of the trough. Mainly fine conditions NE of the trough through northern NSW and SE Queensland under the influence of the ridge with isolated showers on the NE Queensland coast. Possible storms in the SW with the trough. Widespread rain & storms in the Atherton Tableland region and into the Northern Territory. Warmer conditions return to WA as the heat trough reforms along the west coast during the next couple of days & the ridge building through the Bight strengthens the easterly flow. South Australia will see isolated showers in the southeast following the front & a general SW flow will become established except in the NE.
|19||Clyve Herbert||A very nice cold air field over the Aus Bight at the moment, one of the coldest thermal troughs I have seen this time of the year at 500hpa just north of this rapidly deepening low which may fall below 960hpa tomorrow (Wed 20th Feb).With a bit of luck the strengthening jet north of this low may catch some of the moisture from northern Aus tonight and spread it south into SE Aus Wed and Thursday.|
DP's are rising rapidly across Victoria with figures ranging between 12C and 18C. Some stations have recorded some awesome increases in DP over the last 6 hrs (from 6am til 12pm) with the notable ones being Shepparton (up 6.5C) and Hay (up 7.0C).
BoM going for a chance of low topped, non-severe storms on the E ranges of Vic in the area from Echuca - Eildon - Mallacoota but given the current moisture increases we could see that extend slightly further S into the Seymour - Yea - Mansfield area. The sounding for YMML sounding this morning is almost very nice. The biggest problem further S is likely to be the extremely dry air above 900mb (with a DP of -30C just above 900mb). Further to the N and E this should be a tad more moist and more conducive for storm development.
These marked increases in sfc moisture should make tomorrow more interesting but I think Melbourne could be seeing action too early for anything too serious (although with the progged shear severe storms are possible anywhere E of a line from Swan Hill - Stawell - Warnambool). AVN is hinting at the best instability being in the NE of the state near the border with LI's of -6 to -8 and CAPE of 1600 -1800j/kg just over the border into the eastern parts of the Riverina. Given this progged instability and the relatively warm upper level temps, AVN must be going for some decent moisture levels - possibly too much - but then given the increases today, things seem to fit a little better.
|19||Clyve Herbert||The tropical low over the Northern Territory is still a potential risk especially if this system gets over the Indian Ocean off the Northwest of Aus, the low has a very strong divergent upper outflow support, at the moment the whole system is slowly edging westward.|
|19||.||Discussion: The ridge of
high pressure will contract from the Bight to the Tasman Sea & strengthen. A broad
ridge of high pressure along the Queensland coast will be maintained by this high. The
east Australian trough is lingering through western Queensland through NSW and will remain
slow moving with moisture feeding down from the tropics into the Tasman. Pressures
over the north of Australia remain low and the ITCZ extends from tropical Queensland,
through the Tennant Creek area to the Pilbara low in Western Australia. A strong
moisture flow south from this area is feeding into the trough moving through the eastern
part of West Australia & South Australia during Tuesday & Wednesday. The
west-east temperature gradient in the mid levels (850hPa) is steepening as the system
moves east. A thermal trough trails the surface front but appears likely to only
Future Developments: Clearing conditions in NSW as the trough moves slowly NE. An E-SE flow will continue to be directed onto the southern Queensland coast with only isolated showers while the tropical Queensland coast will see some heavier falls. The low over the NT will continue to move slowly west. Temperatures in the SW of WA will moderate with an onshore SW-S flow as the WA trough, & the front in the Bight move east. Strengthening N - NW winds over South Australia on Tuesday & Victoria during Wednesday will see temperatures rise sharply from a mild start to the week before the passage of the front. This trough looks to deepen as it approaches Victoria.
The area to the north of Suva should be monitored for the possible development of a tropical cyclone over the next 24 hours.
|18||Clyve Herbert||I can't help but admire the spectacular monsoonal low over the top end of the Northern Territory at the moment, complete with a huge upper outflow support and strong low to mid level convergence, one can only imagine what would develop from this set up if it was over the ocean, with a major trough approaching from the west some of this moisture associated with the tropical low over the NT may spread south into south-eastern Aus on Wednesday, this should pose some interesting possibilities in respect to storm potential.|
|18||Nick Sykes||Wednesday is looking very interesting,
looks similar to last Friday, squall line. BOM describing this as an active change and
will be a very interesting day. Certainly could be. AVN has LI's of 1200 over Melb @ 3Z
Weds (2pm) and 1600 just to Melbs NW, Ballan type area. LI's are -4 over Melb and to the
NW. Shear looks potentially very nice with a northerly at the surface, strong NW flow @
850 (30+knots) and good winds backing to the WNW @ 700 (45-50knots) and continues around
the WNW up to 300 at about 50-60knots.
500mb and 300mb temps aren't the best but I think there will be plenty of lift with the front, nice temp gradient.
Moisture is good at the surface with drier air up
high. (major dry out ahead of the front)
Atm I think we will see an early morning cloud
band, a clearance for a hour or so before the front and then a lovely squall line coming
through (that's what I'm wishing for)
|18||Clyve Herbert||The very persistent and interesting tropical complex over QLD is a system of Quantum potential, to pin point the centre/s of convective development is like hitting the gopher on the head at a fun parlour game i.e.. aim for one head and another pops up somewhere else!. Anyway, this area is still operating although a little weaker today, the centre of vorticity can be found northwest of Renner Springs, while another convective area is located over the eastern Kimberley region, the area north and northeast of Fiji still looks ok for potential over the next 1 to 3 days.|
|17||Clyve Herbert||A feature of this tropical disturbance is the rather large size of its influence, showing a huge area of upper divergence with very good outflow to the southeast through central and south-eastern Aus. The area of low to mid convergence is also large and somewhat disorganised although there is still good potential for this system over the next 6 to 18 hours, especially if the region of low level convergence becomes organised over the Gulf waters region. Another area of interest is a very positive convective region north and northeast of Fiji, this locality has been persistently active for a few days, the region though appears dominated by the upper equatorial jet moving from the east to the west around 5 south, there is however a strong low level north-easterly surge moving towards the equator from the northern hemisphere presently reaching the near equatorial regions at about 15 to 20 north, this surge may tighten up the ITCZ over this region as the low level pressure surge crosses the Equator over the next 2 or 3 days.|
|17||.||Discussion: A trough is
moving through NSW. A strengthening ridge is directing SE winds onto the Queensland coast.
The ITCZ extends across tropical Australia from the Queensland tropics through the
Barkly Tableland to the West Australian heat trough & is generating mainly overcast
conditions with scattered storms throughout the north. A slowly weakening ridge of
high pressure is located south of WA, running through Bass Strait to the Tasman Sea.
Future Developments: The trough moving NE through NSW will stall during Sunday over the central coast to mid-north coast. The strongly convective area over the Gulf of Carpentaria is showing reasonable outflow, especially in the SW quadrant and should be monitored for futher changes. The West Australian heat trough will deepen and move eastwards into early next week & is likely to trigger showers & storms through the Goldfields, while a passing front will extend cooler conditions throughout the south. This ridge of high pressure is likely to weaken slightly during the weekend and into the early part of the week. The east Australian trough will stagnate over western Queensland over the next day or two, triggering isolated storms in that area as well as through the northeast of South Australia as the available moisture increases. Showers are likely in the south & west of Tasmania early Sunday, contracting to the SW into Monday. Temperatures should increase towards midweek. Victoria should remain mainly fine and mild in a continuing southeasterly flow, with temperatures increasing towards midweek as winds become more NE-N'ly.
Potential risks: Storms are likely through the Hunter & north coast of NSW through Sunday - there is the potential for some of these to be severe with strong winds & hail. It looks likely that the tropical low over the Gulf of Carpentaria will deepen further during the next 24-48 hours if it remains over water.
|16||Clyve Herbert||A nice hot spot over the eastern Gulf of Carpentaria this afternoon,with a huge outflow region and some rather good low to mid convergence keep an eye on this area.|
|15||Anthony Cornelius||Certainly looks like Friday has some nice
potential with the approaching trough. AVN is running a broad area of instability (forgive
me for lack of knowledge of place names) but through central west Vic and into the SW and
central districts of NSW. Broad area of -4 to -6, with some narrow (no real truth value)
-6 to -8 LI bullseyes in some areas.
The upper temperatures will be quite warm (from my understanding of storm situations down here), 500mb temps are only progged down to -11 to -12C. This concerns me a little, not so much the warm upper temps - but -6 LIs with -11C at 500mb and surface temps in the mid-high 30s (even pushing 40) is equating to a mixed DP of 15-16C, which will be at the upper end of the potential tomorrow. There is a slightly moister slab of air sitting over the far east of the state and in SE NSW (can see it on the satpic), and while I'm very encouraged by the direct Tasman-Sea NE flow over most of Victoria, I still think (as is nearly always the case), moisture is going to be a problem. Possibly a double whammy - upper level moisture will be high and a lot of cloud has built up over SA over the past 12hrs, so that will be a waiting game to see whether or not that breaks up or not and how much of an effect that plays. I certainly would like to wake up to a nice skies of broken ACCAS though!
In saying this, I don't believe moisture will be such a problem to the extent that there won't be storms - they'll just be high based. 850 temps are warm (in the low 20s I believe at a quick glance) but the bottom layer will probably end up being super adiabatic anyway so the cap shouldn't become too much of an issue.
Shear is rather nice, particularly around Melbourne and the far SW of the state. Again off the top of my head from flicking through a few charts, surface 15-20 knots NE, back to NNW 20-25 knots at 850mb, NW 30-40 knots at 700mb, 40-50 knots WNW at 500mb and WNW 55-60 kots at 300mb. So some backing with height and good speeds, but the bases will probably be so high that they won't feel much of the low level backing.
I think that things will develop rather latish, eventually becoming isolated to scattered TS and perhaps a squall-type line behind it on a cooler southerly change. Upper temps will be warm, so hail may not be such a big issue - but still large hail is certainly possible. Storms should probably move too fast to give flash flooding (although a 5mm shower can flood Melbourne! <g> but the dry air could certainly result in a few nice dry microbursts. The high bases should hopefully provide a nice CG show.
|14||David Jones||Guy's I'm not suprised the talk is of a
signficant thundery outbreak for Victoria tommorrow, with a very deep near adiabatic layer
stretching from near the surface to 700hPa across most of SE Australia e.g., last night
the 700hPa (~3300m) temperature in Melbourne was just 2C, yet the surface temperature
reached 33C yesterday afternoon. The only thing holding back storms presenting is the
relative shallowness of the moisture in the boundary layer... the surface dew points are
respectively, but overlayed by quite dry air. For those with a window, the instability can
be seen in the form of some decent Cu currently over the eastern and central ranges
visible from Melbourne.
I think the general thinking is that we will see the advection southwards of some moisture from NSW and Queensland where there is some exceptionally moist air a long way south and west (precipitable water near 50mm). With the front acting as a trigger and frontal passage expected through central Victoria late in the day, Victoria looks "primed" for some decent storm action. This scenario is mapped out by the model progs which all suggest widespread rainfall tomorrow... possibly locally heavy.
|14||Nick Sykes||AVN this morning worries me. 500mb temps
are progged to warmed alarmingly for Friday over the Melbourne area (up to -8 to -9 at 9Z,
up from -11 to -12 @ 6Z). This is a marked rise and results in a marked stabilisation of
the atmosphere around the Melbourne area. This seems to be a result of the injection of
still warmer air from the north.
Now moisture continues to be a worry. AVN seems to be downplaying the amount of moisture coming into this system now.
A tricky one to predict, but critical on moisture input, without it it will be just hot and windy. The moisture has made it about as far south as Bourke atm, so a lot of work still to be done.
|13||Clyve Herbert||Although there has or seems to be little interest in a persistent disturbance that has been playing about the Derby to Wyndham area over the past 5 days, which has shown reasonable outflow features and a region of positive convection, this area of development has now decided to go and play over the sea west of the Mitchell Plateau. Still showing not too bad outflow characteristics although low to mid convergence is a little on the weakish side, worth keeping a look at over the next 6 to 12 hours.|
|13||Andrew McDonald||Well - interesting to wake up this
morning to a forecast of "chance of shower or storm on the central and eastern
ranges" for TODAY!!!! It was always going to be a very slight chance but the main
features which this depended on was the available moisture (which seems to be slightly
higher than *everyone* initially had in mind) and also on the upper level temperatures.
The second feature being more difficult to pick. An upper trough is progged to move over
us today and with some OK moisture inland in both Vic and NSW (which is relatively deep
from what I can see on the obs from the ranges) we should see some convection. AVN is
progging 850 temps of 16-18C across central Vic and 14-16C across in the east. A normal
storm day would see the E ranges go up earlier than the rest and I think today will be no
exception. The higher peaks to the E will probably help break the weaker cap out there and
convection should spread across the ranges by late in the day. AVN shear is typically
quite weak with 0-6km shear of 20knts at best. A weak jet of 30-35knts will at least move
some anvil outflow away from storms somewhat, meaning they won't be totally pulsey. Storms
should move in a SE'ly direction so for something to affect Melbourne we'd need to see
stuff form W of Kilmore - Seymour area (possible - BoM mention in their aviation forecast
that showers and storms are possible E of 143E on and *just* S of the ranges). The 4am sfc
analysis displays a weak ridge which arcs across towards the Bight, cradling a very weak
trough. This is progged to dip down into western central Victoria today and may aid in the
development of stuff today as well.
Concern for today: Apart from the fact that I have to work tonight (meaning storms will be spectacularly photogenic), I'm a tiny bit worried about moisture levels. I won't be around to look at the soundings for YMML and YSWG this morning but I noted yesterday that in the NW of the state the sfc moisture mixed out rapidly once things warmed up sending DP's crashing below zero. This indicated some dry air not far above the sfc. There is a possibility that the PBL has moistened up overnight but we won't know until the heating kicks in over the next 3-5hrs. A quick look at last night's sounding for YMML shows a nice (relatively) moist PBL and with upper temps progged to drop a bit today and warmer sfc temps we should see some activity if the moisture can maintain itself.
Some indicators are pointing at more activity tomorrow as well as Friday. Of note for Friday is the developing cloud in central southern WA - is this going to play a part in reducing the chances of a storm for Friday? More to come tonight/tomorrow.
|12||.||A large high in the Australian Bight is
ridging to the south of Tasmania and building a ridge along the NSW & SE Queensland
coasts. The low in the Tasman Sea will move SE towards the South Island of NZ.
Weak TC Claudia in the southern Coral Sea is drifting southward. The ITCZ
extends from TC Claudia across north Queensland, Northern Territory with an extension of
the trough running southwards through Western Australia. Current synoptic conditions
are generating a few showers on the SE coast of Victoria, along the east coast of NSW,
& storms are occurring over central north Queensland associated with the ITCZ.
Widespread showers and rain areas are affecting the Top End, while a tropical disturbance
over the far north of WA is bringing increasing potential for the development of a cyclone
in this region if the system moves offshore from Derby. A few showers and storms extend to
the Pilbara along the WA trough. The rest of Australia is remaining generally fine
Future Developments: The high in the Australian Bight will gradually move along the baric ridge south of Tasmania to the south Tasman Sea, initially weakening, then restrengthening midweek east of Tasmania. This will strengthen the ridge along the east coast although it will remain rather broad. The ridge will also continue to affect SE Queensland. The tropical disturbance will continue to develop in the Coral Sea bringing coastal showers & drizzle will persist along the NSW coast By mid week the east Australian trough will be deepening from inland NSW through to Victoria. Increasing moisture along this trough should lead to late afternoon showers or thunderstorms. The ITCZ should remain active across north Queensland, the Top End and the Kimberley, bringing outbreaks of rain with some heavy falls, particularly in the Top End. The trough extending southwards through WA will deepen Tuesday & Wednesday when the southern portion gradually extends into South Australia. Victoria will come under the influence of a NE - E flow as the high moves into the Tasman Sea although a relatively weak trough during Wednesday & Thursday may generate showers and storms along the ranges. This trough will become absorbed into a more substantial trough moving in from South Australia during Friday & Saturday.
Potential risks: The ITCZ continues to be active across the tropical regions of Australia with continued potential for tropical disturbances in the Coral Sea, Gulf of Carpentaria & off the NW coast of WA. At the moment, upper level support tends to favour the development of tropical storms west of Darwin, although this will be improving over the Coral Sea and the Gulf region later in the week.
|11||Clyve Herbert||Several areas of interest at midday east Aus time today (11.02.02.). An interesting but small area of positive convection near Derby WA is showing rather good upper divergence and small but good inflow, seems to be moving westward, this area of activity has been paddling about the lower top end for a couple of days, some potential if this disturbance gets itself over open sea, also the Gulf of Carpentaria is looking better although the upper divergence is dominated by stronger easterlies above 300hpa while the divergent field to the south is rather weak at the moment. The tropical disturbance moving over the southern Coral Sea is showing some weak organization but looks to be too far south and may be enveloped by cooler air moving through the north Tasman today.|
|11||.||High pressure ridging south of Tasmania
& into the Tasman Sea. Satellite low becoming absorbed into the main low near to New
Zealand. Broad trough running across the northern NSW coast & along the Queensland
coast into the tropics. Showers along the NSW coast are likely with the rest of the
state remaining fine. Moisture plume from the low in the northern hemisphere has become
detached. Monsoon cloud from the eastern Coral Sea area is being drawn into the low
to the east of New Zealand causing the monsoon trough to be more southwards over the Coral
Sea than over Australia. With the pressure building south of Western Australia &
also south of Japan, the convergence over northern Australia has strengthened.
Seasonal storm activity through the Queensland tropics merging to rain areas through the
Top End & northern parts of WA. The heat trough over the west coast directs a very
warm E-NE flow particularly across the central parts of the state and these conditions
will affect the more eastern parts of the south coast as the day progresses and the trough
moves inland, while the SW corner & west coast will cool as the trough & the front
to the south move east. South Australia will see temperatures increasing as the SE
winds back to the E as the high passes to the SE. Winds across Victoria & Tasmania
& showery conditions will abate during Monday, and temperatures will begin to rise.
North of the ranges in Victoria will remain fine.
Areas to watch: the mid & upper level baroclinic region in WA which marks the position of an upper trough. The low pressure area in the Coral Sea for improving organisation & divergence aloft.
|10||.||Pressure seems likely to
remain fairly low across SE Australia into early next week. Currently the low in the
Tasman is moving towards New Zealand & deepening, while the high in the Bight is
moving east but weakening, so pressures are relatively unchanged. Showers, with possible
hail & thunder may be triggered in the south of NSW as a front moves northeast with
500hPa temperatures dropping sharply with its passage. Coastal showers are a risk in the
S-SE flow onto the coast. The trough off the Queensland coast will move westwards tomorrow
& Monday. Mainly fine except in the tropics, especially around the Gulf of
Carpentaria. The area of low pressure near Wyndham is showing improving divergence but
with rather fragmented convergence, while the area in the Coral Sea is showing better
convergence. A moisture plume extending from a large low in the northern Pacific can
be traced to the area of convection in the Coral Sea. This may help create an area
of enhanced convergence located between the Coral Sea and Fiji.
Widespread shower & storm activity over the Top End & northern WA. The WA heat trough will deepen just off the coast, and together with the high in the Bight, will direct E-NE winds across much of the state maintaining fine conditions except possibly in the southern Pilbara & Gascoyne where moisture levels are on the increase. South Australia will continue to have unseasonably cool temperatures with drizzle along the southern coast through Sunday. The mid-level 'cool pool' in the Bight south of the WA-SA border should be watched for signs of destabilisation as it approaches SA during Sunday. Showers over Tasmania clearing through Sunday. Unseasonably cool conditions in the SE of the country. Victoria should also see showers through Sunday, with possible hail & thunder in the south as the mid-levels cool behind the front.
|9||Clyve Herbert||Some interesting stuff over the Australian region at the moment, significant activity over the top end as the ITCZ starts to work on all cylinders, the area around the Top End is starting to show enhanced low to mid convergence and there seems to reasonable upper divergence, although the bulk of activity is well over the land south of Darwin. The area around the Coral Sea has ok low to mid convergence but lacks upper divergence at the moment, all of this tropical area of Aus is primed with sea temps 29 to 31C. At the opposite end of the scale there is a rather interesting cold pool south of Mt Gambier and west of Tasmania, as this system works northward tonight it will react to progressively warmer sea temps 17 to 19C near the Victorian coast this cold pool area shows some positive vorticity between 500 and 300hpa.|
|9||Nick Sykes||The models are ponting to a substantial period of heat over SE Australia (Victoria) from mid next week, with temps in the mid to high 30's. The models have a high moving into the Tasman and what looks like a blocking low deepening out near NZ. This type of setup can result in extended periods of northerly winds for SE Australia. Not too sure about the storm chances atm, if there is moisture in the northerly flow we could see some storms, though often the case with these situation is that strong upper level ridging develops as a reult of the heat build-up.|
|9||.||The upper low which spun
up on Thursday off Mt Gambier & moved into the west central district of Victoria
Friday morning, continues to move NE during Saturday across NSW while drawing moisture in
from ex TC Chris. Cooler air wrapping in around the low at 850hPa will destabilise
conditions & there is a risk of storms associated with the passage of the upper low
across the state. Clearing to the west as the surface trough moves east. Moist
NE'lies will cross the NSW coast bringing the risk of isolated heavy falls especially to
the south coast of NSW as well as eastern Victoria, with further showers in the south of
Victoria while conditions are likely to be mainly fine in the north. Scattered
showers are possible in the NW of Victoria under the influence of the remains of ex-TC
The influence of this trough extends through to the southern part of the Top End. A drier S-SW flow will become established as the trough clears southern & central Queensland & moves northeast. Tropical storms continue through the weekend & the monsoon trough remains active over the Top End, while seasonal storms will redevelop in the northern parts of WA with the clearing of the area of the influence of ex-TC Chris. The heat trough will deepen down the west coast while the high in the Bight will continue to direct a cooler, showery SE flow onto the southern coast & much of South Australia. Weak front passing Tasmania through Saturday should trigger showers over the southern parts especially.
Areas to watch: .... the cloud patch in the Indian Ocean near to the WA coast for a developing upper disturbance as the area captures an infeed of moisture from TC Francesca. The upper low SW of WA is also expected to capture some of this moisture during early Saturday. The interaction between the cloudband returning from the Tasman across the NSW coast & eastern Victoria due to the interaction between the upper level circulation & the surface trough may see some heavy falls.
|9||Clyve Herbert||News of what I would consider to be an extraordinary rain event over parts of western Victoria and some parts of the west central district are filtering in from farm settlements between Cressy and Colac, farmers checking their gauges on Friday morning have found them full and overflowing and unable to record more than the 250mm that their gauges can hold, most of this rain fell between 0300 and 0900 hrs (not confirmed) estimates of totals between 200 and 300mm have been reported in a band extending south from Cressy to near Colac. These areas have annual means of between 545mm and 650mm,and means for the month of February are about 35mm!, this would have to be pretty close to some sought of record with totals of between 600 and 800% of the monthly ave coming down in one night!!, in some cases an amount of 300mm is close to 60% of the yearly mean. Observation of the sat pic showed an intense but narrow wrap around band associated with rapid cyclogenisis that moved over this region between 0300 and 1000hrs on Friday.|
|8||Blair Trewin||Two sites that I know of topped the ton -
Lismore at 122.6 and Beeac at 113.8. Both these sites are N/NE of Colac. Both values are
all-time records for the sites concerned (with 80-100 years of record) - previous records
are 108.5 on 6/2/1973 at Lismore, 89.2 on 30/11/1933 at Beeac.
No Otways site got over 100 (although the flood warning that's just been issued for the upper Barwon says rainfalls of up to 64 metres have occurred in the catchment!). The heavy rains at Aireys Inlet and surrounds seem to have been the result of local storm activity (Aireys got 73mm between 0400-0700 this morning) rather than more general onshore flow.
|8||Lindsay Smail (GWS)||Beeac 114, Aireys Inlet 93, Torquay 93, Barwon Heads 89, Mt Gellibrand 81, Anglesea 75, Paraparap 74, Modewarre 71, Cape Otway 68, Birregurra 62, Winchelsea 61, Marshall 60, Boonah 59, Inverleigh 50, Weeaproinah 48, Mt Cowley 43, Mt Duneed (Geelong AWS) 42, St Albans Park 40, Shelford 39, Hamlyn Heights 36, Bannockburn 35, Manifold Heights 35, Forrest 34, West Barwon Dam 34, Sheoaks 33, Mt Sabine 29, Wooloomanata 26, Avalon 23, Lara 22. Latest 30-year February mean for Geelong is 34.3 mm.|
|8||David Jones||Of course it is
still too early for the 9am reports, but there has been some impressive
rainfall totals from last nights storms and this mornings
rainband through central Victoria (focused on the Otways
region). High fall so far is 93mm at Aireys Inlet, but one could reasonably expect somewhere to have cracked the 100.. Also note that the
heavy rain has penetrated significantly inland (Lookout Hill getting
64mm). All up, probably not enough rain to produce much in
the way of flooding. The situation over Victoria today is
quite tricky, as the upper low drifts NE towards the Sydney
region. There will certainly be some further significant
rain, but the exact placement will depend on the orientation of the cloud and rainbands around the surface trough and upper low. Melbourne
currently, sits between heavy bands to the south, east and west! but
when the low level flow becomes
more southerly could become favoured for some heavy rain -
the situation is not unlike that which produced the very heavy rainfall March last year.
Also, I notice that the models are starting to get a little more bullish about the follow-up cold front on Sunday, with thickness values now being progged to drop to around 540-548 over southern Victoria late Sunday. At the colder end we could see some heavy rain and hail showers develop and possibly some cold air thunderies (given the "warmth" of bass strait and the bays), and even some snow flurries around the peaks of Lake Mt and Baw Baw...
|8||Lindsay Smail (GWS)||Movement of that low eastward resulted in clockwise band of t/s across Geelong & Bellarine Pen between 3 and 4 am moving from NNW with centre somewhere west of Meredith, but by 8 am another band moving up from SE with centre around Laverton. In 3 hours from 3am; at Modewarre 71mm, Marshall 60mm, Mt Duneed 26 mm, Aireys Inlet 45 mm, Grovedale 26 mm, Torquay: 85 mm between 3am - 8am. Clyve was right (again!!)|
|8||.||The vorticity centre that was evident SW of Mt Gambier in the middle levels Thursday night has intensified over the west central district of Victoria and will move only slowly east over the next 24 hours. This may also capture some of the moisture from ex TC Chris. Rainfall totals are likely to be well over 25mm in some areas near to the low & may be much higher in some parts of central Victoria as well as SE NSW, the latter especially Saturday as the low moves over the Tasman. Storms are likely with this system while the mid levels continue to cool. The inland trough from Queensland to the low in Victoria will trigger storms along its length as it deepens and moves east. Moist NE flow onto the NSW coast will also lead to showers east of the ranges. Extensive seasonal storm activity continues across the tropical north of the country. The area near Nhulunbuy is of interest. A weak heat trough lies just off the WA coast. The high ridging through the Bight in combination with the low over Victoria, will direct cool, moist southerlies across the SE parts of SA. SE-E along the southern coast of WA. Rain areas in the central parts of the state will contract eastwards over the next day or two.|
|7||Blair Trewin||This sort of humid SE setup is ideal for extreme rainfalls in the Otways - quite similar to the April 2001 event in some ways. I won't be at all surprised to see totals in the 100-200 range from favoured locations tomorrow morning, especially as Weeaproinah's already had 64 and it is somewhat sheltered from that direction (it's ideally situated for W/SW flow, hence its high annual mean, but places like Tanybryn and Mt. Sabine, on the oceanward side of the range, tend to get higher extremes, most dramatically in the March 1983 event when Tanybryn got 375 and Weeaproinah 'only' 115).|
|7||Harald Richter||TODAY: Lower
boundary layer moisture and lower surface temperatures indicate
that today is not going to be a repeat of last Friday. However ... I like the upper levels more than I did last Friday. At 23Z YMTG suggested cool mid-levels and disorganised flow. Since then, the MTG profiler points to freshening mid-level flow with 25
knots from 340 at 1:30Z. With that tendency continuing, flow
would be significantly up on last week.
Then AVN has a 70 kt jet nosing into the Mildura region at 500 by 06Z, putting us into the right forward quadrant supporting lift. A reasonably sharp surface wind change / trough has set up in extreme SW VIC, extending from Warrnambool through Casterton into SA. A meridionally oriented line of convection is approaching the longitude of Cape Otway to Colac, but the lightning tracker shows (almost) zilch? The inland BL airmass E of the wind change averages surface parcels around 24/11. Enhanced sea breeze/bay breeze convergence is setting up from W of MML down the coastline past Geelong, with convection located between Geelong and Anglesea.
The Cape Otway-Colac line and SW Geelong convection is the obvious "cat-in-the-bag" play for today. The best air would be nearer the coast, maybe right along the sea breeze front. I wonder whether the combination of stronger upper-level flow and higher surface T,Td is going to produce something bigger in NE VIC later?
Or, what about the good W Gippsland moisture later?
|7||David Jones||I think if nothing
else this developing system will give Victoria (particularly
the eastern half) around 36 hours of "wintery"
weather starting tonight. Last nights soundings showed a nice
moist atmosphere from the near surface to around 300 hPa over
Melbourne (and further east). Very interestingly from a
rainfall perspective, the dew point depression was uniformly around
5C, meaning that even a moderate amount of vertical motion
will see rapid development of thick stratiform cloud and
rain. Of course, the approaching thermal trough (currently
south of the bight), and development of a sharp baroclinic
zone over western Victoria which is then expected to give rise to cyclogensis will provide the necessary lift. Personally, I wouldn't be
surprised to see a few 25-50mm falls clocked up out of this event.
As for storms... these certainly look quite likely this afternoon, though I would expected a rapid change over to more general stratiform rain this evening.
|7||.||The upper low that has been located over
the SE of NSW for the past few days may interact with the deepening trough over western
Victoria and push south & rejuvenate. Victoria should see possible showers &
storms merging to longer spells of rain, with rain periods continuing through Friday.
NSW should continue to see humid & showery weather for the next day or so with
an increase in storm activity to the west of the ranges closer to the trough axis,
especially in the north of the state. Scattered storms will again be a feature of the
trough running through eastern & northern Queensland with hot & fine conditions in
the west. The area around the Gulf of Carpentaria should be watched.
The northern part of the country will be under the monsoonal influence which is steadily becoming more active, with widespread seasonal showers & storms, particularly in the east. Outflow from 'Chris' covers the northern half of the continent. Widespread heavy rains are likely over the Pilbara & west Kimberley area, extending south & east through Thursday. Hot E - NE winds are directed across southern WA and into the heat trough located off the west coast. The ridge through the Bight will maintain cooler conditions on the southern WA coast. There is a risk that some mid & upper level moisture from 'Chris' may be drawn towards the SE of the continent as the 300hPa jet strengthens along its southern edge. This could affect the northern parts of South Australia where there may be rain periods, while in the east there is a risk of isolated storms under the influence of the deepening trough. Scattered showers for Tasmania.
|6||Nick Sykes||Thursday still has the potential to be
very interesting, I am not ruling out the possibility of widespread storms, with some of
them being severe. The mid and upper levels continue to be very cold. AVN has 500mb temps
of -17, 300mb temps -45. 850 temps remain around the 10 mark but have the potential to
rise as the trough deepens. Temperatures in the high 20's, around 30 will make things very
I will certainly be watching the skies thursday. Interesting to note AVN now has CAPE values exceeding 1000 over Melbourne at 9Z Thurs...(not the most reliable) With the upper levels as cold as they are and with potential for high CAPE values, large hail could be a feature.
Will be interesting to see where the trough is positioned at prime time Thursday (5-7pm).
|6||Clyve Herbert||Just as TC Chris has now moved ashore (and still showing up as severe over land 1500esst), a positive convective area that was east of Cape Wessel yesterday has now moved to be west of this area this afternoon and northeast of Darwin. There seem to be two rather large scale convective areas within this whole region - one near to the NT central north coast and another well to the north. this region is showing rather good low to mid convergence but still lacks upper level divergent support but nevertheless seems to be a risk area for further development over the next 6 to 12 hours. Also the cut off upper low that has been plodding about the southeast of Australia over the past several days can be seen as a region of enhanced vorticity north of Griffith NSW, this area of positive vorticity may lumber towards the south and interact with a developing trough over western Vic today and tomorrow.|
|6||Andrew McDonald||Well.....today is an interesting day. A
mid level low over SE NSW is weakening and drifting away although leaving some cooler
mid-level temps across the E parts of the state. E - NE'ly flow across the E ranges today
combined with some moderate sfc heating should kick off some weak convection over the
ranges. I don't think we'll see anything too serious though - maybe the odd Cb over the
Alpine National Park. The BoM have mentioned the far W of the state as being a chance
today as well as the inland trough starts to deepen through the far far west of the state.
Moisture levels out there are OK with DP's of 10-12C but I'm not totally convinced that
there will be enough convergence along the trough for lift to kick off storms. Mt Gambier
sounding shows some potential. A slight increase DP and a temp of about 28-30C will see
things kick off today out west. Looking at this morning's Melbourne sounding temperatures
of about 27-28C will be required with a PBL of about 10C to kick off storms on the ranges
but again nothing of too much significance is expected. Looking to the NE around to the NW
of Melbourne there is some Cu going up but a moist, warm layer between 750 and 700mb is
causing these Cu to flatten out a bit. As it warms up these Cu should push through that
layer but a second cap/inversion/warm layer at 600mb should see most Cu supressed here.
Any Cu that gets above that layer could potentially keep going and produce a weak storm.
I'll be watching from the comfort of my computer room, keeping an eye on the TC (no pun intended) and also on today's convection in the W of the state.
Tomorrow is another matter. Tomorrow (Thurs) is looking *extremely* interesting IMO. A strong shortwave upper trough is progged to enter the W of the state during the afternoon. The sfc trough is progged to deepen further tomorrow and progress E'wards across Victoria, sitting close to Melbourne by about 8pm tomorrow night. NE to N'ly sfc flow into this trough should bring in some additional moisture. I'll be happy if I wake up to 13-15C DP's tomorrow across central districts. 850 temps are progged to be between 10 and 14C (depending on which model you believe) giving potential sfc temps of about 26-34C across the state. Given those temps, the cap should be moderate, supressing convection until mid afternoon. The upper level shortwave trough will see upper level temperatures cool to -17C at 500mb and -44C at 300mb (which is very nice for this time of year). Of note is the comparison b/w the YMML and YMTG soundings today. The YMML sounding is relatively moist all the way up whereas the YMTG sounding is quite dry above 800mb. If this dry air moves across western/central Victoria tomorrow (quite likely) we could see some very interesting storms develop. Shear is again marginal although IMO better than Friday just gone. The shear is strong enough IMO for organised storms to develop especially along the trough and other localised boundaries which may exist (ie the sea breeze). Given the progged shear, storms should move more ESE - E'ly tomorrow. There is also a chance of storms on the E and NE ranges tomorrow as well but these storms will be forming in a weakly sheared environment with somewhat less instability than the areas close to the trough. I think the best areas tomorrow will be along the trough given the upper level support pushing in. I'll be looking in the morning for places with additional moisture and as the day goes on also the sfc temps (the higher the better in both cases). Severe storms are possible in the eastern parts of the Western, Wimmera and Mallee districts and Central, North Central and Northern Country districts tomorrow for large hail (given the upper level temps and dry air I'd think hail to golf ball size is not out of the question), damaging winds (in the form of straight line winds and also a very slight chance of tornadoes) and also heavy rainfall is possible. There is also a *slight* chance of severe storms over the North East and Eastern districts for very heavy rainfall (given the weakly sheared environment but the moist sfc air).
|6||.||Trough in NSW is getting a boost of moist
infeed from the outflow of TC Chris as well as the convective area in the Gulf of
Carpentaria. Ridge up the NSW coast has halted the eastward movement of this system
particularly in the south, leading to further widespread falls & the potential for
some flooding mainly to the east of the Great Dividing Range (GDR). That part of the
trough located in NE NSW - SE Queensland shows signs of shearing into the Tasman under the
influence of the 300hPa jet, leaving the southern part behind to affect the SE of NSW
& NE Victoria during Wednesday. Clearing through western NSW. The trough in Queensland
will trigger thunderstorms along its length & the area around the Gulf of Carpentaria
is worth keeping a close eye on as it has shown signs of improving organisation over the
past 36 hours.
TC Chris will cross the coast during Tuesday night / Wednesday morning & remain slow moving over land. Widespread heavy rains are likely over the Pilbara & west Kimberley, while the trough along the west coast shifts southwards, maintaining a hot easterly flow & isolated storms in the SW of the state. The high in the Bight ensures that South Australia remains mainly fine under a SE-E flow, although there is the likelihood of an increase in mid level moisture in the east of the state later Wednesday. This moisture, together with cooling mid levels will lead to a destabilisation of conditions in the west of Victoria later Wednesday with isolated storms developing. There is a chance of storms along the eastern ranges during the afternoon. Light rain over the east of the state remains likely under the influence of the upper low in southern NSW. Isolated showers on the eastern coast of Tasmania, remaining unseasonably cool.
|5 1642AEDST||Clyve Herbert||TC Chris at 1630 is showing a classic
look of a mean tropical cyclone, now at Cat 4 and still deepening pressure at the centre
around 927hpa winds max up to 265kph, there is still some risk of Cat 5 later tonight
although I think this system may max out at the higher end of Cat 4, the tracking of this
TC still seems to be south southwest which puts it at the moment making landfall between
(wide) Port Headland and Wallal downs and a core central track through or near to Pardoo
Roadhouse later tonight or early tomorrow.
This TC is EXTREMELY DANGEROUS and hopefully will change course or move across uninhabited regions. Another area showing persistent positive convection is just east of Cape Wessel off the NT coast although upper divergence is rather weak
|5||.||Upper low with an associated cold pool
has moved over NSW & NE Victoria & may have its eastward movement stalled by the
surface ridge along the coast which will also continue the low level moisture injection to
the area. Upper level moisture infeed has shifted to be more from the Gulf of
Carpentaria rather than TC Chris. Risk of widespread heavy falls continuing through
Tuesday in NSW. Trough over Queensland will continue to trigger isolated storms
along its extent, with some heavy falls expected. Convective area over the Gulf is
disorganised but is showing high moisture levels concentrated in the area & should be
watched. Coastal showers are likely for the Coral Sea coast. The Top End has
tropical storms moving towards the NW.
TC Chris looks to cross the coast as per Clyve's prog & then may continue to move southwards before being captured by the subtropical jet. Heat trough off the WA coast will remain unchanged for the next day or so with TC Chris dominating the area. Scattered showers & thunderstorms likely for the western parts of the state. South Australia will see generally fine weather. Tasmania looks to experience warming conditions as the high moves into the Tasman Sea. Although the heaviest falls are to be expected along the east coast of Australia, South Gippsland and Otway coasts see a risk of light to moderate rains during the next couple of days. Watch for a risk of a wraparound cloudband across southern Victoria during the next day or two.
|4||Nick Sykes||Been surveying the models and it looks
like the next best day for storms in Victoria and Melbourne is this Thursday.
Thursday has the makings of a very interesting day. Heaps of moisture will be funnelled into Victoria over the next couple of days from the east.
A surface trough is forecasted to deepen over Western and Central parts of Vic on Thursday. The upper levels are expected to be quite cold. Temperatures at 500mb are progged to be about -17 over Melbourne at 5pm, -44 @ 300, 850 temps are expected to be to be 10 to 12, so surface temps in the mid-high 20's can be expected. If significant heating occurs things could become very unstable. Li's are predicted to be down in the -3 to -4 range with CAPE near 1000. Shear is o.k, but has the potential to improve with a jetstream moving in from the NW. Moisture at the surface is great, RH of 90%.
Now moisture is my main concern, the upper levels look to be moist which may result in quite a bit of middle/upper level cloud.
EC and NGP all go for a significant trough system over Vic on Thursday.
Now for a bit of a dream outlook. The models are hinting at quite a strong upper trough, moving into from the SW. If this upper level system were to link up with the surface trough we could see very nice instability. This scenario may come into play later Thurs in the west and east on Friday. At this stage it looks like this system will play behind the surface trough, but worth a look.
Oh, and watch for possible storms on Wednesday, if the winds go more to the NE. All we need in Vic would be some clear air and the central and eastern parts could see storms. Clearance being the key.
|4||Clyve Herbert||T.C. Chris has reached cat 3 and still edging slowly southward, wind gusts near the centre are approaching 180kph and the system is still deepening, if TC Chris remains over the sea it may reach cat 4 later tonight. The present track if it continues puts the TC crossing the coast between Anna Plains and Wallal Downs, there is some risk of the TC moving slightly to the west of this area.|
|4||.||In New South Wales, the inland trough is
tilting to be further east in the south. An increase in the moisture field over inland NSW
courtesy of TC Chris, along with showers along the coast which are the result of the ridge
up the coast, means that much of NSW could see moderate to heavy falls through Monday.
Scattered thunderstorms with some heavy falls can be expected mainly west of the
ranges. Inland Queensland will also come under the influence of the trough & can
expect enhanced shower and storm activity in the vicinity of the trough. A weak
ridge along the southern Queensland coast will direct SE winds onshore with possible
coastal showers. Seasonal storm activity throughout the north of Australia in a
westerly monsoon flow. WA heat trough is located off the coast with hot NE'lies
across much of central & southern WA with the risk of isolated storms in the west,
while the NW of the state remains under the influence of TC Chris which is slow moving at
present but extending its influence along the coast and across the Pilbara. Upper
low developing in the Bight with an associated cold pool at 850-500hPa is likely to move
SE through southeastern SA & Victoria during the week. TC Chris is feeding upper
level moisture across towards the SE of the continent and we may see the development of a
mid level low or trough over the next 2-3 days with a destabilisation of conditions
through Victoria (again!). There is a risk that Tasmania may experience light showers and
Of interest is a low with an extra-tropical signature to the SW of Sumatra at ~15S!
|3||Andrew McDonald||After a stormy start to the weekend today
finished with a cool day, which as Blair mentioned on the TWC forum was the coolest Feb
day in 4 years or so (18.5C). There were some weak showers and storms in far SE NSW close
to the Vic border along the inland trough but I think cloud prevented heating and hence
only relatively weak convection occurred (that I know of).
Tomorrow is going to be an interesting day. The inland trough will deepen slightly and push SW wards into NE/North Country districts of Victoria. Currently a large NW cloud band runs from WA down across most of Victoria. I think this cloud band will be the feature which will determine whether or not there are storms in Victoria. The latest satellite loops show the cloud band slowly drifting across Victoria with the western edge now sitting just W of the border (the 22:30 image). Of more interest is the clear slot pushing into the NW of the state. I think the cloud band will drift far enough E overnight to leave at least half of the state clear tomorrow (W of 145E). I also think the "clear slot" could potentially move far enough E to sit close to, if not right over the sfc trough tomorrow. The clear slot most likely indicates drier air pushing into the W edge of the cloudband. If the area E of a line from Echuca - Bendigo clears to allow some heating into the area near the trough, some convection should kick off. Upper levels are slightly cooler than late last week and 850mb temps are quite a bit cooler too meaning that deep convection will require less heating to initiate. A guesstimate at a convective temperature tomorrow would be about 28C. Given that the sfc winds are progged to be E-ENE across the NE and Northern Country tomorrow not a lot of heat is going to be drawn from warm inland areas so the heating will depend almost solely on the cloud clearing. Dew points in the far NE of the state are sitting between 11 and 13C and with more moisture sitting in SE NSW waiting to be transported into Vic by the NE'lies tomorrow, these DP's should increase a little tomorrow making things more interesting. AVN is currently progging this entire cloud mass to virtually cease Sward movement as of about now (given its current position) and then shift due E meaning that the clear slot lies across the Central West areas of NSW. S of the clear slot has more moisture (and hence cloud). Due to this they are progging the best instability to be in the Central West of NSW. The idea is right in that where the clear slot interacts with the trough, storms will kick off but the question is still posed as to where the clear slot will be. I think the current sat pic indicates that this clear slot will be further S than AVN is progging and there is a chance that we could see it sitting over the northern parts of Victoria at prime time tomorrow.
Of course I'm working so I can't chase but wherever the clear slot lies it will be worth keeping an eye on the area. Shear is going to be quite good with sfc flow being NE'ly and the potential is there for mid to upper level flow to be quite strong from the NW. If deep convection can be initiated I wouldn't rule out organised storms with the chance of severe storms with the works (hail, winds and heavy rain).
I'll be interested to see where the cloud lies Tues and Wed as well as I think there is a chance we could see Victoria virtually cloud free with most of the cloud sitting JUST over the border in NSW (hehe) which will leave our skies clear and primed for storms...hehe. This may depend on what happens with the TC currently sitting just off the WA coast (and incidentally is now progged to be Cat 3 within 24hrs of it being named) and the direction it moves and the interaction it has with the jet.
|3||Clyve Herbert||T.C. Chris has at the moment some very nice outflow spiral bands, surface convergence is not as good this afternoon, the system seems to be edging south,southwest, also there is some potential over the southeast of Australia for the risk of a cut off low developing over the next 24 to 36 hours although the sub tropical jet is not as yet attained good divergent outflow to the east. Some nice looking storms over the WA region inland from Carnarvon along the surface trough , enhanced convergence also occurring here as this trough deepens with the approach of TC Chris|
|3||Clyve Herbert||The area of convergence and enhanced convection that has been playing about the Kimberley area over the past 5 or 6 days has finally moved offshore and managed to get its self under a region of good to very good upper divergence, if this system continues to develop we may see one of the better TC's of the season. There are, or seems to be two preferred alignments of movement one towards the west, north of the 500hpa to 300hpa ridge or a recurve towards the south southwest, (the upper ridge appears weaker further west), it may then harass the northwest coast of WA between Exmouth and Port Hedland keep an eye on this one.. also there is a small region of enhanced convection west northwest of Thursday Island but this development is under rather weaker upper divergence, another system is apparent well to the west of AUS near to the central Indian Ocean at about 10 south. The cloud band extending through SA is also starting to interact with outflow from the developing TC north of Broome - this band has some potential as well.|
|5||Clyve Herbert (1st Feb Hailstorm report)||Most of the hail that fell around Melbourne extended from Laverton through Newport and then across the southern half of the CBD, hail also affected the near southern suburbs and sporadically across the eastern suburbs. The hail size varied between small (pea size) and up too 2cm, however there were observations of hail up to golf ball size (4+cm) from along Spencer street and along the extreme south side of the CBD including Flinders street and Southbank. There are some unconfirmed reports of broken windows from large hail around the Balaclava area.. The structure of the large hail (4cm)was interesting, some were conglomerates and appeared larger than 4cm (combination of several smaller hailstones) while others were true singular large hailstones up to 4.2cm, these larger stones were very sparse and when handled some were strangely slushy in nature others were harder. The slushy stones may have indicated that they were close to 'end of life' after falling more than 13.000ft in progressively warmer air above the freezing point, all stones were rapidly melting. Apart from some trees being leaf stripped I heard of no significant damage caused by this hail event.|
|1st February storm reports||Reports & photos of Friday's storms can be accessed from the MSC main page - or click here|
|1||Andrew McDonald||As pointed out by Dr Jones on the this
morning, moisture levels have increased significantly across Victoria overnight with dew
points currently ranging between 13C and 18C with a clear dew point gradient running from
east to west (with higher DP's in the E). I think the PBL will be a tad drier than this
and we should see these DP's mix out later this morning/early this arvo and they should
come down to a more accurate indication of the PBL of about 12-13C. The YMML sounding this
morning is quite nice with -1.9 LI's on it and only a plotted temperature of 30C. With a
temp of 33-35C this sounding gets quite nice. The sounding is quite representative of much
of Victoria up to about 350mb but above that is where things get interesting. As mentioned
yesterday, an upper ridge is pushing into the W of the state so the sounding should warm
somewhat throughout the day above 350mb - this warming can already be seen slightly on the
23:00 UTC sounding at 300mb. Given the sounding I'd think garden variety storms will top
out at about 28-30,000ft or so but stronger storms should get quite a bit higher, hitting
about 35-36,000ft. Shear is very marginal on the sounding but I'll discuss this a little
The trough is progged to be in the W of the state at about 4pm running from about Lorne - Mortlake - Swan Hill. Storms should fire near the axis of the trough with some nice convergence. The trough will be clearly defined as it was yesterday and I wouldn't want to be on the wrong wide of it as it will be dry with S'ly winds. The ranges will also kick off storms today given the unsettled nature of the day. 850mb temps are progged to warm slightly throughout the day from 16C to about 18C which should aid in capping convection until later on. The ranges should start to fire around Mt Baw Baw, Mt Hotham, Mt Buller after 2pm, other ranges will go closer to 4pm with the plains (off the ranges) probably going even later - close to 5pm. Of course the cap will be slightly weaker in the S so the SW areas near trough could potentially go a little earlier if they get some decent heating.
Shear across the state is quite marginal but not as slack as yesterday (although I was surprised by the anvils of the storms getting dragged off to the SE on a jet which looked to be about 25knts which was a bit more than progged). Given the shear progged by AVN and the BoM's aviation forecast, storms should move generally NW to SE but again storms could move in weird directions due to propagation. Although the shear is marginal I think there will be just enough for storms to be somewhat organised. Given this and the fact that upper level temperatures are relatively cool I think we could see some severe storms today. Central, North Central, North Eastern, South/West Gippsland, Eastern and Alpine districts should all see severe storms. Note that these are all E of a line from about 144E - I think the upper level ridging will not allow for convection to reach severe levels (storms should still form along the trough but i don't think they'll be the best ones - they could, however, flatten to thundery rain later this evening giving us Melbournites a nice show tonight). Heavy rainfall leading to flash flooding (given that storms will be moving relatively slowly), damaging winds are possible and some large hail is also possible. I would speculate that hail could get as large as 3cm in the strongest storms today E of 144E especially in elevated areas where the FZL is lower.
While typing it looks like a cell popped up and down again to the WNW of Sale which is interesting. We could see things go a bit earlier than anticipated if heating gets in before the cap increases a bit. Given that its already 30/16 at my place and hitting high 20's/low 30's across much of central and north central Victoria, storms *may* take off early than initially thought. Some nice AcCas is sitting on the ranges at the moment and some Ac extends across to the western suburbs of Melbourne.
I'll be staying here for a while, watching and waiting. I don't think I'll be chasing west of 144E and given the current situation I think the area bounded by Melbourne - Seymour - Noojee - Mansfield would be a good start for today. I also think Seymour - Mansfield - Bright - Albury will be OK today. For those who like to sit and watch it happen from a distance a few places to watch from are the fire tower at Kangaroo Ground, Doncaster Shopping Town carpark and Mt Dandenong - all places have great views in almost all directions.
|1||Clyve Herbert||The synoptic set-up developing over the Australian region is looking promising, the cloud area in the Tasman has been edging south-westward for almost a week when this area of convergence was north of NZ, I also agree with "Doc Jones" there is something cut-off looking about the set up for the southern part of Australia and the southeast of the continent is looking better for this situation, not a bad field of cold air moving into the south-western Aus Bight area as well. It would be nice to see this cold air region mucking about with the increasing tropical/sub tropical moisture now feeding into much of eastern Aus..keep a lookout!|
|1||David Jones||Based on persual of
the observations and progs, I suspect it is a wise move hanging
around Melbourne at least to lunch time.
There is always uncertainty, but I wouldn't be surprised if the best action occurs very close to Melbourne. The instability indices in the models are tending to maximise through central Victoria, as is mid level moisture (700hPa RH approach 100% for tonight), while the local aspect and topography should yield healthy low to mid 30s temperature across the Melbourne metro area through the afternoon in the broad ENE to NNE surface flow. Melbourne is also going to be relatively close (this arvo) to the surface trough currently over western Victoria, which should provide some low level convergence.
Looking out the window, the scattered Ac and odd bit of castellated Ac points to (at least) reasonable mid level instability and moisture, while inthe low levels dewpoints have increased by 3-5C since this time yesterday (we even had a good dew this morning at Ferny Creek with a minimum if 15C which points to quite a depth of warm humid PBL air).
BTW gazing further into the future, it seems that yet again the northern end of the thickness trough associated with the front crossing the waters south of the Bight is expected to "cut-off" from the more southerly section near Ceduna and then stall. At the same time, the high approaching Victoria first ridges, then establishes its main centre south of the mainland. Such a scenario often precedes the development of easterly dips through NSW and Victoria and eventually cyclogenesis... certainly something to watch for..
|1||.||In NSW, convergence around the low edging southwards from the Coral Sea may trigger moderate - heavy falls to the central & south coasts, possibly extending to the north coast. The increase of moisture through the interior of NSW may lead to locally heavy storms ahead of the approaching trough. In Queensland, progressively increasing moisture through much of the state will see an increase in locally heavy thunderstorms particularly in inland and northern parts, although the southward movement of the Coral Sea low may also create favourable conditions on the SE coast with the possibility of locally heavy showers. Through the NT, a positive convective area in the west of the Territory may inhibit activity over the eastern Top End temporarily due to upper subsidence, although there will be abundant surface moisture available. Storms may merge to longer spells of rain particularly through the west & in central regions over the next several days. In Western Australia, a region of moderate convergence over the Kimberley and to the west may see the development of a TC over the next few days offshore. Much of the NW of WA is still experiencing positive convectional conditions which may lead to large scale storms with heavy (possibly very heavy) falls especially in the north Kimberley region. In the event of a TC developing, 2 tracks are possible - a progressive westerly track or a recurving track which may bring the system across an area near Port Hedland (or a track somewhere inbetween). The remainder of WA will see sporadic storm activity spreading south as far as Kalgoorlie, but remaining in the general area of the heat trough. South Australia, apart from drizzle near to the Bight coast in the early morning & the chance of thunderstorms in the northern areas, some of which may be high based, there is a tendency for a gradual increase in moisture in the next few days which may bring substantial rains by at least July. In Victoria, the presence of the trough on Friday, which will probably be captured by an eastward moving front, should be sufficient to trigger storm activity Friday & Saturday, with a possibility of moderate falls & isolated heavy falls, then showers contracting to the south coast and ranges, before turning to drizzle Monday morning. As winds tend SE - E, as a high ridges south of Tasmania, the trough will develop in the northeast of the state, a few storms may develop again early next week, and then spread to affect most parts of the state by mid-week.|
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