Victoria - May 2001 Forecast Outlook, Discussion & Report Page



May 2001 Forecast Outlook, Discussion & Report Page Victoria
Date	Name	Information
.	.	Victorian Weather Glass
29	Clyve Herbert	A marked convergence line looks interesting over the south west of WA at the moment. Some rather large anvils one of which seems to show a slight anticyclonic curve - this area looks like it may generate some good storms today especially with a thermal trough moving over this region later today, there seems to be a risk of a possible severe storm or two this afternoon.
23	Nick Sykes	Weekend Low - Model Discussion GASP has the system weakening as it moves over SE Australia. Going from a 995 low in the Eastern Bight at 12Z on Saturday to a 1010 low over the SE inland on Sunday 12Z, this is a substantial weakening and seems to coincide with a marked weakening if the associated cold pool and the fact the low will move over land, killing it's moisture intake. By end of the weekend and early next week GASP has a very nice looking upper level low developing over NE NSW. The very cold upper level temperatures associated with this upper low will certainly aid any thunderstorm development. Therefore it appears the best weather associated with this low will be over the South Central and SE of SA. The low and associated front will be at their most mature at this stage and should generate respectable rainfall, falls in the order of 15mm+ quite likely. As the low weakens as it heads east it will generate more patchy rain over Vic and NSW. The best falls will most likely be on the lee of the Ranges in Victoria and the SW of Vic. As the low is forecast to go quite deep on Saturday as in approaches the SE, the pressure gradient will be quite tight, resulting in windy weather. Strong northerlies will result for Victoria ahead of the low which will also see the rainfall rates in Central and Eastern Victoria (south of the ranges) been less, due to the rain shadow effect of the divide. As the low moves further east next week Eastern parts of Victoria may see some heavy falls as the low drags moisture onto the coast. NGP is timing this system similar to GASP, with a deepish low and associated cold pool in the Eastern Bight region at 12Z on Saturday. It then has the low moving into Southern NSW as GASP has, with the same associated surface weakening. The associated upper level low is forecast to maintain strength and move NE into NE NSW where it is likely to generate some interesting weather, most likely storms. As for Vic it looks like the best upper level support will bypass us, though it still looks as storms may be a possibility, especially if any convergence lines develop off the low. Overall I think this system will peak too far west for Vic to see any significant rain from the surface low. Then it looks like the very nice upper level low will move NE and bypass Vic and therefore miss the best storm potential. Wind will be the stand out feature in Vic with this system and a lot of high cloud. Nick Sykes & Vic Storms
23	Nick Sykes	A weakish front is moving up from the south and will affect Tasmania and Southern Victoria overnight and tomorrow. This front will increase the shower activity in areas mainly exposed to SW winds. Not a lot of rain can be expected with this weak system. Some cold air behind the frontal band may result in some snow falling to lower levels in Tasmania, down to 700m. This frontal system will also freshen the winds along the coastal regions of the SE, and wind warnings are current in many locations.
22	Lindsay Pearce (NSW)	The latest GASP run has a sub 540 cold pool over the south east (including the Cent. Tablelands) and -2C 850 temps by Tuesday next week and NOGAPS has a similar thickness set-up for around the same time. I'm not sure when AVN's latest comes out so it will be interesting to see it and MRF too. It's looking interesting for some nice cold air, anyway.
20	Carl Smith (NSW)	You will find colour highlighted images of these two disturbances at http://users.ace-net.com.au/~carls/currenttropical.htm along with the area JTWC has a TCFA for in the Phillipine Sea. I have placed T°C bars alongside these images, and alongside the full disk and the regional ones at http://users.ace-net.com.au/~carls/currentsatpics.htm - I calibrated the temp. scale using two versions of a satpic of a cyclone, one of which had been enhanced for Dvorak analysis for which I also had the temperature information. I do not know if these IR temps are universally applicable to geostationary satpics, however if not, they at least give a guide. I am managing to update all these images twice daily at the moment.
20	Clyve Herbert	Although a bit late in the season,two areas of interest still exist in the near Australia region. It's interesting to watch the tropical disturbance north of New Caledonia which although weak can be traced back to a persistent convective area near the Solomons last week. This disturbance is showing weak upper divergence and there is a concentration of surface convergence producing occasional larger cumulonimbus clusters on its northern flank - there is also a weak line of CB's extending northward, it would be interesting to see what sort of surface conditions will accompany this system if and when it crosses the northern part of New Caledonia over the next 12 hours. The other area of interest is in the vicinity of the Samoan region northeast of Fiji - there has been a persistent and positive area of convection in that region and is now showing weak to moderate upper divergence - it's worth watching this area over the next 12 to 36 hours.
19	.	Victorian ASWA meeting - Pancake Parlour, Doncaster. Guest Speaker: Rob Gell
16	Jane ONeill	Images of the low as it tracks across southern Australia http://www.stormchasers.au.com/low_05_01.htm
15	Clyve Herbert	It appears the low south of Adelaide is becoming complex with a new centre of vorticity apparent just west southwest of Mt Gambier,and another centre (old one) further to the southwest. http://www.stormchasers.au.com/Campics%20-%20May/05150807csiroaus.gif http://www.stormchasers.au.com/Campics%20-%20May/05150934jcu.gif http://www.stormchasers.au.com/Campics%20-%20May/0515jculoop.gif
14	Clyve Herbert	There's a bit of activity going on around the Solomon Islands, not very organised but showing some weak potential,also an interesting convergence zone to the south of this area and a very nice and large tropical moisture plume extending across the central Pacific and southward towards Antarctica. A bit of an odd shape to the low approaching south-east Aus: note the Hammerhead concave shape near the centre, I haven't seen this formation too often,seems to be where the wrap around pushes into one of the convergence bands. Eds note: see image links http://www.stormchasers.au.com/Campics%20-%20May/05140730gmsd.jpg http://www.stormchasers.au.com/Campics%20-%20May/05140329jcu.gif http://www.stormchasers.au.com/Campics%20-%20May/05140629jcu.gif Not a bad rainband just west of Woomera at 1800hrs with some greens and pinks, all forming along the primary band associated with the Bight low.
11	Clyve Herbert	Despite the concern that another winter will pass with high pressure control and a lack of westerlies over the southern states, has anybody noticed the progressive decline in surface pressure over much of southern Australia over the past 3 days. Projected analysis was showing much higher pressure expectations which never eventuated, instead a decline and weakening of high pressure control has been underway and it looks as if a phase of cyclonic activity will develop across the southeast of the continent this weekend. Even now there is a weak area of upper vorticicty over western Victoria and another appears to be developing at the head of the Australian Bight. The large area of cold air south of WA also shows good potential. With the present high pressure ridge weakening today and slipping southeast an area of low developing over the Bight might then piggyback over the southern high and affect south-eastern Aus this weekend and early next week. In regards to a tendency for highs to remain at a higher latitude than normal over the past few years a clue must be in part due to the rather warm sea surface temps over the Coral Sea, the Tasman Sea and this year even Bass Strait, which under the relative conditions at this time of the year become somewhat adverse to the persistence of high pressure cells and instead be areas of potential cyclogenisis and this has been the case for the past 5 years or so as Mr David Jones has pointed out. Bring on the lows!!
10	Clyve Herbert	A rather impressive field of cold air just getting into southwest WA, what looks better though is a large grouping of enhanced cold CB's well south of WA, concentrated near a vorticity region within a 500hpa thermal trough, this region may generate a new low over the next 6 to 12 hours.
8	Clyve Herbert	An interesting comment about the fetch of the present cloud band coming ashore on the central NSW coast. An interesting comparison can be made with a similar cloud band that wrapped around the developing low over Victoria on the 21 April 2001 and brought record 24hr/48hr/72hr and monthly record totals to the Geelong area, on that occasion the cloud band had a similar extent.
8	Clyve Herbert	This is a very interesting photo (see below), especially seeing that this waterspout is very close to a populated area,although small the waterspout is relative to the congesting cumulus,this was an interesting day with a light southeast flow and rather mild(about 18c). The lower layers were very moist and unstable with deep low level convection, cu bases were around 300m and tops to about 3000m, there was a weak inversion at about 2000m, lapse rates were very steep in the lower 3000m, but the cu appears to have been driven more through the condensation process than strong surface heating. The previous day there was a weak vorticity centre just west of Mt Gambier, this low level system may have moved just north of central Victoria on Sunday.
6	Lindsay Smail	Waterspout at Lorne - pic taken by Kevin Flynn. Courtesy Geelong Weather Services
1	Clyve Herbert	Some impressive vorticity north of Kalgoorlie tonight, looks like some good rainfall in that area and embedded storms too. Also a very nice looking low over the Tasman, interestingly this Tasman Sea low can in part be traced back to a small wave low that developed along a weakening cold front a few days ago over Victoria and then moved into the Tasman to be enhanced by some pre existing vorticity in that area.