Updated 1700AEST - 30th July 2000

July 2000 Forecast Outlook, Discussion & Report Page

Victoria
Date Name

Information
30 Clyve Herbert Hello 'weather people', The rather spectacular cold outbreak last week brought snowfall from Victoria to far north NSW between 400m and 800m and sea level snow to Tasmania, also useful rainfall to parts of southern Victoria.

This week is shaping up to be under an anticyclonic phase with a tendency for the high pressure belt to persist across southern Australia and for occasional frontal activity to be weak.

A rather large but interesting high level cloud band over SE Australia on Sunday (31st) should gradually dissipate and move to the east on Monday. High pressure should then establish across SE Australia on Monday and persist to at least late Wednesday when  another weak frontal system may reach SE Australia, with the possibility of light showers.

We may then see a decline in anticyclone control from Thursday with the appearance of more active fronts towards Friday and the coming weekend.

Temperatures should remain close to normal throughout the week . Light winds may see the development of fogs and light frosts at times with fogs more likely in southern Victoria and frosts favouring the northern parts of the state. At this stage no significant rain is expected.

RISKS: The upper cloud band across SE Australia this weekend (31st) is associated with a weakening front and an upper disturbance. Although this system appears to be dissipating there is a possibility of further upper disturbances moving across from central WA to SA mid-week. If development of this system occurs it may generate more general areas of light rain across SA and NSW with a slight risk for Victoria from Wednesday to Friday.

Clyve Herbert and Geelong Weather Services.

26 Clyve Herbert (observation) Geelong
Great day down south - very nice cold air field early this morning, snow line about 800m. The arrival of what appears to be a thermal trough around 1200hrs brought the start of the coldest air in Melb CBD. The temp dropped from 10c to 6c at about 1400 this was accompanied by a snow line to about 500m with brief snow down to 400m under larger cells.  Areas along the divide - unconfirmed reports of snow to 350m. I arrived home in Geelong at 1800hrs with a temp of 4c.  Even at my home (only 6ks from Bass Strait), it was 4.5c.  Wind WSW.  A remarkable warming occurred at 1935 with the temp rising to 8.8 after 1930 temp of 4.8c.  This was accompanied by a wind change from WSW to SSW and a pressure jump of 4hpa. It appears the strengthening wind has brought warmer surface air from over the nearby Bass Strait.  I have seen this phenomenon on several occasions especially when associated with abnormally cold air.
26 Chris Daley (observation) Mooroolbark
2mm hail at 17300AEST
26 Jane ONeill (observation ) Mt Dandenong
Late afternoon / early evening - snow (as in large flakes), graupel, small hail - temp was 1.1C, snowflakes were getting down to 480 - 500m & settling on the carpark of the lookout at 630m!!!!!
26 Miguel de Salas (observation) Tasmania
You might be interested to know that it's been snowing non stop in much of southern Tasmania above 500m since this morning at ~6:00, and that snow was settling at 200m a.s.l. in Hobart suburbs at noon. Further snow is forecast down to even lower levels tonight, when the coldest air pool moves over us.
24 Patrick Tobin (ACT) The latest MRF is still running a pretty amazing scenario for Wednesday and Thursday of this week. Even WA sees some cold air with -2 temps at 850hpa tomorrow clipping the southern coast - not sure if this just gives the Stirling ranges the possibility of a few passing snow flakes.

Wednesday looks to be the most interesting day for Victoria (and eastern SA) as the sub 528 pool traverses north over the western district and then swings NE to be over a large area of the NSW inland, slopes and ranges for Thursday; and leaving a smaller cold pool centred over the NSW Northern Tablelands on Friday.

If MRF plays out as indicated, then it looks like the NSW tablelands (southern, central and northern) will bear the brunt. I guess this means the Blue Mtns and most parts of the Central Tablelands are likely to become isolated by road (and rail) for a couple of days and possibly even the Hume Hwy closing for a while. We could also hear reports of snow falls from places as far apart as Mt Lofty, Flinders ranges, possibly central Aust ranges and the Stanthorpe area in Qld as well as numerous lower level stations in Vic and NSW.

MRF also hints at some possible interesting further snowfalls for especially the Vic ranges from the "returning" cold air heading back southward over the weekend. There is always the potential for some interesting effects from any local pools of cold air that end up trapped in valleys or over the inland in the wake of the outbreak.

It all looks rather exciting - the skis remain ready and waiting.....

The above scenario has support from GASP and to a slightly lesser degree the EC.

On the other hand NGP, as Michael observes is not really coming to the party to anything like the same extent - just a strongish but relatively normal winter cold change with not much moisture and some good frosts as the high moves in. My head says that one should place more emphasis on the model that is closest to 'normal' conditions (in this case NGP) ... but the speculation of the more extreme event is much more attractive...
24 Clyve Herbert Things are looking better for our much expected cold outbreak Tues/Wed here in Victoria. A rather nice splotch of mid high cloud near to the head of the Bight looks interesting even showing a weak comma shape and possibly hiding large scale surface convection under an upper cold pool and one of the longest cold air streamflows pushing northward from below 60 south . With thickness at 500 showing a possibility of reaching 524-528 by Wed hopefully for NSW some of this cold air may extend into the central and northern tablelands. But for Victoria look out for the possibility of up to 3 days of cold cb action and snow over high ground especially if the high west of WA continues to strengthen a ridge towards Antarctica.

Clyve Herbert and Geelong Weather Services.

24 Andrew McDonald Thicknesses are varying between 528 and 532 as a lowest figure down S (here) and the 540 line has been seen to have been pushed as far N as Longreach on one model. Now whether this would have enough moisture to generate some interesting weather up that far N I don't know. There is potential for some severe cold-air CB's with this system and after looking at the huge amount of them last night in the cold pool behind the main front I could safely say we'll see a few of them here and there reaching severe status. 500mb temperatures are forecast to drop below -30C into NSW and below -34C in the S. South Australia should see some pretty intense weather today/tonight and probably easing by Wednesday. I think we'll see things start to become interesting tomorrow and easing off by Thursday with Wednesday probably being the most interesting of the days. Snowfalls are possible down to about 600m and heavy falls are likely above 1000m as of tomorrow night. I wouldn't be surprised to see up to 60-70cm of fresh snow up on the higher Victorian ski fields and probably 40-50cm on the lower ones such as Baw Baw, Donna Buang and Lake Mountain.
24 Clyve Herbert Hello 'weather people',

Following an interesting week of strong winds and general rain and good falls over parts of southeast Australia and Tasmania, and excellent snow falls across elevated parts of the dividing range, the trend of 'active' weather will continue for the coming week with even better prospects for good rainfall/snowfall.

A rather broad long wave trough continues to affect the Australian Bight region with a very favourable area of low pressure around 50 degrees south, with some of these lows at times approaching 950 hpa.

Another interesting development is a strengthening high south west of Perth. This system looks as if it will push a ridge southward towards Antarctica on Sunday and Monday assisting in the process of cold air advection towards southeast Australia Tuesday to Thursday.

Cold fronts will affect south east Australia sporadically from Sunday to Thursday.

Showers, some locally heavy, are expected Monday to Thursday and a mass of very cold air should arrive late Monday or Tuesday with possibly heavy falls of snow affecting high ground. Snow and sleet might extend to lower levels i.e. 300 to 500 metres on Tuesday or Wednesday.

From Tuesday the large high south west of WA should push slowly east to reach the Australian Bight by Thursday or Friday. Strong winds are expected to affect southeast Australia from Sunday to Wednesday. Temperatures should remain cold to very cold especially on Tuesday and Wednesday. Frosts will increase in sheltered inland areas from Tuesday to Saturday.

Precipitation will be enhanced across the Divide and near the Otways and heavy accumulations of snow should occur, especially above 1200 metres. A settling trend is probable from Friday to next Sunday as the large high increasingly influences southeast Australia.

RISKS:
Very cold air advection across the Australian Bight and waters west of Tasmania on Monday to Wednesday might see this area becoming favourable to major cyclogenesis. This could lead to increased precipitation over Tasmania and parts of southeast Australia. For western Tasmania there is a risk of severe flooding, while near record snowfall accumulation across the Tasmanian and Victorian high country is likely, especially above 1400 metres. Significant rainfall is also a risk over the Otway Ranges with enhanced stream flows possible.

Clyve Herbert and Geelong Weather Services.

23 Patrick Tobin (ACT) The models are continuing to suggest quite a strong cold outbreak for SE during the middle of this week (and I will certainly enjoy it whether or not it is as strong as May).

The latest run of the AVN 191 model accessed through NOAA's READY site has 1000 - 500mb thicknesses of less than 526 centred on NW Victoria (around Mildura) at 12z on Wednesday with 500mb temps of less than -35!!

NGP (while not quite as intense) has a large area of sub 540 streaming well north and almost into the tropics. GASP and EC are also consistent with a substantial cold outbreak.
22 Andrew McDonald An interesting set-up is forecast for early-mid next week with a decent looking cold outbreak forecast. Here is a quick analysis of what the models are telling us and my forecast of likely events as a result of these models. Before I get into it we can expect some more vigorous NW'ly winds preceding the passage of the front due to the tightening of the pressure gradient as we have seen over the last few days.

NGP:
Front forecast to move into Victoria sometime Monday afternoon with follow-up fronts/troughs likely in the vigorous and unstable SW'ly airflow expected to be generated by a low pressure system. Where this low pressure system sits will depend on how intense this system becomes. The further S the less intense basically. -29C forecast over S Vic @ 500mb for Monday night.... just below -30C by Tuesday morning.....possibly down to -31C ,during Tuesday before heading back closer to -30C by Tuesday night......then warming fairly quickly overnight Tuesday to about -25C by Wednesday morning. 850mb temps are staying above -3C, probably dropping as low as -2.5C at the time of the coldest air. This give a pretty steep lapse rate between 850mb and 500mb which could make the showers/storms a little more grunty. I think with a system like this we could expect 450-300mb temps in the vicinity of -47C to -50C so some reasonable strength cold air Cb's are not unlikely in the post frontal SW'ly airstream (which as I mentioned earlier will be pretty unstable). Thickness is forecast to drop as low as 532/531 in southern Victoria with the 540 line and below freezing 850mb temps are forecast to reach a fair way into the Central Tablelands of NSW. There is also a fair bit of precip and moisture forecast for most of the duration of this system (drying out a little towards the end - later Wednesday) which could result in some heavy snowfalls above 1000m and lighter, but still significant snowfalls to about 600-800m.

GASP:
They also have the front moving through on Monday - perhaps a little later than NGP. The GASP charts are a little harder to analyse as they only give thickness and surface pressure. So I guess the only real comparison to be made is the thickness and GASP and NGP are in agreeance to some extent with GASP going a little harder and putting it down closer to 530.

MRF (9 day panel - extended outlook):
Although this model is fairly outdated and much less detailed compared to the others it still reflects the system in the charts. It is different somewhat though, in that it pushes through the initial front overnight Sunday before the more vigorous front moves through later Tuesday, leaving colder air hanging about until Thursday and maintaining the SW'ly airstream until Saturday morning. It has a fairly significant decrease in thickness, bottoming out somewhere in the low 530's which seems to be fairly standard for all models thus far.

AVN:
The current model run (out to 3 days) takes us to Monday morning. AVN seems to push a prefrontal trough through late/overnight Sunday before the main front on Monday. This could generate some nice rainfall totals ahead of the colder weather and although not good news for the ski fields, its great news for all the farmers. AVN have thickness dropping below 540 in Melbourne during the day on Monday which is interesting considering the 850mb temps aren't looking to drop below zero until late Monday/early Tuesday (probably with the passage of another front/trough).

Overall, the models tend to agree on a few factors. The first being the significant amount of moisture present in the prefrontal environment. This to me suggest a prefrontal cloud band, most likely to be a rain band with a slight risk of embedded thunderstorms amongst it (AVN raw data has LI's of 0 to -1 forecast). The next is the vigorous, cold and unstable W to SW'ly airflow forecast to push through with the surface front/s Monday and Tuesday. And finally the cold upper air which is forecast to move into the state Tuesday.   The last two factors are  likely to result in snowfalls to fairly low levels (maybe as low as 600m but more likely to 800m) and some cold air CB's in Victoria. Overall, it should be an interesting few days in the lead up to it to see how it shapes up and then an interesting few days during it to see how it performs. Hopefully it'll give us Victorians something to talk about at the next ASWA meeting (next weekend) as I think the past month has been a little lean in terms of significant weather events.

For those who don't know, we have a report on the significant weather events each month which have occurred since the last meeting. It has become a regular part of the agenda at our meetings and is very well hosted by Clyve Herbert who passes on his extensive, in-depth knowledge of surface charts, satellite pictures and general observations to all of us (thanks - much appreciated).
17 Andrew McDonald Been doing some checking of the models and it turns out that Wednesday could be more interesting than first anticipated.  AVN is currently forecasting lifted indices down to -3 around 1pm Wednesday with CAPE up to 400j/kg which is pretty impressive for winter.  After checking the humidity data sets though I think if anything is to happen, it is more likely to be embedded storms rather than isolated storms (although storms could develop behind the cloud band if we are lucky).  The main cause of this is the pretty decent upper system expected to come through with the front.  I think we could see some action come Wednesday although I don't think it'll be as organised as we'd like.
16 Andrew McDonald In addition to Clyve's forecast I'd just like to point out the potential for a decent blast of cold weather come mid-late week. There seems to be a series of cold fronts to push through over the next week and a half with the one due mid-week looking to be fairly strong.  Current forecast temperatures are for 13C and I've noticed in the last few days that the TV stations have been throwing in a few higher forecast temps - I'm wondering whether the lack of a decent cold blast has lulled them into a sense of forecasting warmer weather.

NGP has the 540 line well N of the Vic alps, even stretching a fair way into SE NSW. 500mb temps are currently forecast to drop below -30C over much of Vic and thickness forecast to drop below 534, possibly down to 531 over S Victoria. I guess with these figures we could/should expect some fairly decent snowfalls on the higher elevations and even some snowfalls down to about 800m (maybe 600m on Wednesday night). There is potential for some cold-air CB's on Wednesday night and into Thursday morning as well - there should be a decent cold pool being dragged up after the main front goes through. This system is forecast to blast through fairly rapidly and we should see showers clearing rapidly by later Thursday as the next ridge pushes into our region.

As I mentioned earlier, a series of cold fronts are due and the end of the weekend should see another front enter the area but I think it will be a slightly more typical front with some snow showers on the higher peaks and showers in southern and mountain areas. All in all though there is potential for a decent top-up of snow on the alps over the next two weeks. I shall hazard a guess and say, going by the current models, we can expect about 35-40cm on the higher resorts and probably 20cm or so on the lower ski fields.

16 Clyve Herbert SYNOPTIC CONDITIONS: Weather systems continue to "traffic jam" over waters south of Australia. This is due to a persistent and strong High southeast of NZ. The Tasman Sea is also favourable for cut-off Low pressure systems that have been moving in a southwesterly direction for almost a week.

Last week, low pressure systems dribbled across the Australian Bight to cross Victoria, SA and into NSW, occasionally bringing lively weather to inland eastern Australia as the occasional upper cold pools reacted to surface heating. This produced unseasonable storm activity as the upper disturbances moved over the warmer Tasman and producing Low pressure.

The large High southeast of NZ has shifted its ridge northward from near Macquarie Island and large weather systems are now moving southeast from the Australian Bight with the northern frontal extremities affecting SE Australia.

A weak front is expected to pass over Victoria early Sunday (16th) bringing showers to southern and mountain areas. A large high should then strengthen over inland SA bringing settled conditions Sunday through to at least Tuesday (18th). Frosts and fogs are probable over inland Victoria Sunday and Monday(17th).

A major frontal and Low pressure system appears likely to develop west of Victoria on Tuesday and affect SE Australia late Tuesday to Thursday. This trough and front may bring moderate and possibly heavy falls of rain especially to southern and mountain areas. Some rain should also fall in northern Victoria.

A colder trend is probable Wednesday to Friday (21st) with showers and snow over high ground.

RISKS: A Low pressure system may develop in the cold air field near Victoria on Wed - Thurs. If this occurs rainfall and mountain snow may be enhanced.

Clyve Herbert and Geelong Weather Services.

12 Michael Thompson (NSW) Some of the models are hinting at a major outbreak of cold next Tues - Wed. GASP, NGP and MRF all hint towards 5400 thickness to come well over SE Australia. Unlike the last couple of fronts the 5280 is not far behind and may affect us too. GASP has an intense low of 964mb SW of Tasmania on Tuesday with the cold air coming up behind it. There is a lovely jet coming up from way down near Antarctica driving it all too.
9 Laurier Williams (NSW) For several runs now, GASP has been predicting extraordinarily low thickness values over SE Aust for next Friday and into the weekend. The latest run (00z) has sub-528 values over eastern Victoria on Friday and Saturday morning as a surface low forms in eastern Bass Strait, then the cold pool blobs off and runs up the ranges to be over about Wagga with a 527 thickness on Sunday morning, at which time 850hPa temps are between -2 and -5 over all Tas, Vic and most of NSW.

I'd hold off waxing the skis just yet, but there is good support for the general concept of an unusual cold outbreak late this week and into the weekend from the other models, too, though they're not quite so OTT. All of them retain and strengthen the blocking high east of South Island NZ, and stall the high now moving in from the west over southern Qld or western NSW around midweek. At the same time, they strengthen a ridge connecting the two highs in a long loop down to around 55S -- in fact, both the latest GASP and yesterday's US model both have the highest pressure (around 1027hPa) 1000km south of Tasmania (!!!!) on Friday morning. This is an extraordinary looking map, and the consequence would be a long southerly fetch of very cold air directed towards SE Vic/NSW/Tas, and a slow south to SW movement of a developing Tasman Sea low. Definitely a situation worth watching.
8 Clyve Herbert SYNOPTIC CONDITIONS: Hello weather watchers! An interesting upper low disturbance was located over Southern NSW on Friday afternoon, and a cold front was approaching Victoria from the Bight. This front should move across the state on Saturday - Sunday.

The cold front should be accompanied by general showers and outbreaks of more prolonged rain along the Dividing Range and southern areas. The frontal system should then be followed by showers Sunday-Monday in those areas also.

Showers should become more isolated late Monday - Tuesday before the arrival of another frontal system on Wednesday - Thursday, with more showers and colder conditions on Friday and Saturday. Some showers may be locally heavy on Thursday.

TEMPERATURES: Should remain cool to cold through the week. Some frosts are likely in sheltered areas at times. Snow showers are likely on the Dividing Range especially above 1400m.

RISKS: The large high south of NZ is slow moving and this may cause the low pressure system SW of Adelaide to move over Victoria on Sunday. Although this system might weaken it may still intensify shower activity on Sunday - Monday.

Clyve Herbert and Geelong Weather Services.

6 Rutherglen (observation) We have had 18mm today and a thunderstorm has just passed along the Murray river to the north of here. About 5.30pm-6.30pm looked to be heavy rain in it but we just got the edge of it.
6 Matthew Pearce (NSW) The encouraging thing at the moment is the breaking down of the ridge from the NZ high over eastern Australia. Although still present, it is significantly weaker than over the last week, and this has allowed the fronts to push further east before sliding down to the southeast under the high. The next front does hold a lot of promise, with some nice upper level support, and still plenty of moisture input from the NW cloudband streaming across the continent. Both EC and GASP are going for a closed surface low to form on the front south of Adelaide with a sharp thermal trough moving across the SE early next week. However, once again the highs are well to the north behind the front, so it looks like widespread snow falls will be unlikely. On and west of the NSW southern ranges should see something though, with cold, frosty mornings looking likely towards the middle of next week once the high takes over.
6 Rod Aikman (Bendigo) Was awakened just after 04:00 this morning by some decent claps of thunder, followed shortly after by hail pinging on the iron roof. Not a bad effort from a cold front that was forecast to fizzle out to a band of patchy rain by the time it reached Victoria.
6 Rutherglen (observation) Heavy rain here this morning (Rutherglen) at 5.55am with a very severe lightning strike just to the SW of the town. Went to ground for a second or more and the thunder was almost instantaneous, so it was close. Another strike shortly after but my eyes hadn't re-focused from the first strike so I'm not sure where it was. Barometer has dropped 6 overnight and still falling slightly. Raining heavily again now (7.50am).
6 Harald Richter (Norman, OK) My summary of it is probably the old song:  with the L centred SW of Perth a few days ago the *pre-frontal* flow (on the surface) could collect plenty of moisture flowing over high(ish) SSTs along the West coast.  The result was an unstable atmosphere as cooling was observed aloft - and Perth got a good show out of it as I remember. Surface pressure in SW Western Australia dropped at least below 1002 hPa at the time. Now, at 000706/1600 UTC, SE South Australia shows the lowest pressure around 1010 hPa, with the pre-frontal flow pulling down *continental* (i.e. dry) air into Victoria. The post-frontal air should be unstable enough for footy weather (that's part of the old song, too).
5 Nick Sykes Looks like a nice NW cloudband forming from a low in The Indian Ocean. Moisture is being fed into the SE from the NW. GASP and EC have a low forming in our region around Sunday and with the good infeed of moisture there could be some nice rain. Best falls on the Ranges. Will probably fall as rain on the Alps, killing the snow ):
2 Clyve Herbert SYNOPTIC CONDITIONS: The large high over SE Australia should move eastwards Saturday and Sunday. The deep low in the Tasman Sea should continue to move away to New Zealand. As the high moves east of Victoria on Monday and Tuesday a trough should advance into Victoria probably on Wednesday.

Some patchy rain should accompany the trough with showers to follow on Thursday and Friday.

TEMPERATURES: With the high over SE Australia on Sunday-Monday, frosts and fogs will develop over inland Victoria. Conditions will be cloudy at first in the south on Sunday with some fogs developing. Conditions over this period should be cold, with a milder trend on Monday-Tuesday. A freshening wind and a colder trend will be experienced from Wednesday to Friday.

RISKS: A large cloud band over the Northern Territory should be watched on Sunday for possible developments as it moves southeast. There is a possibility this may generate patchy rain across eastern NSW and Victoria on Monday.

Clyve Herbert and Geelong Weather Services

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