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#15163 - 21/09/2004 09:18 Re: South Australian and Adelaide day to day forecasting
Helen Offline
Moderator

Registered: 07/11/2001
Posts: 9633
Loc: Mid North, SA
Looks like it's going to get rather warm today, perhaps even hotter than is forecast... already 20ļC here and even warmer in Adelaide. eek
_________________________
2017 YTD - 67.8mm Yearly Average - 403mm
Jan - 32.8mm (10mm) / Feb - 35.0mm (10mm) / Mar - - (15mm) / Apr - - (31mm)
May - - (46mm) / June - - (51mm) / July - - (59mm) / Aug - - (54mm)
Sept - - (48mm) / Oct - - (38mm) / Nov - - (23mm) / Dec - - (18mm)
Total 2016 - 637.2mm



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#15164 - 21/09/2004 11:20 Re: South Australian and Adelaide day to day forecasting
Ricky Offline
Weatherzone Addict

Registered: 21/09/2003
Posts: 1567
Loc: West Richmond
Indeed, we just hit 27 here and its not even 11am. I would be looking at at least 31 atm if not higher.

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#15165 - 21/09/2004 17:18 Re: South Australian and Adelaide day to day forecasting
Thunderstruck Offline
Lightning man

Registered: 10/05/2001
Posts: 14800
Loc: Seaford Meadows, SA
Hmmm not making it over 30C! Comp still alive atm!

Tuesday 21/9/04

Fine and warm to hot conditions prevailed over much of the state. Moderate northerlies brought down a fair bit of inland heat and as a result temps are nearing 30C in the central districts and are nearing 40C well out west such as Nullabor. Adelaide reached 29.7C, and there has been some Altocumulus during the day due to a trough of low pressure to the west. This will not cause any significant weather for Adelaide.

Wednesday 22/9/04

A weak cold front with associated weak pre-frontal trough will move over the Adelaide region during the morning, causing temperatures to drop and winds to shift moderate South westerly. The wind change should arrive about 8am with a shower or two likely sometime during the afternoon or evening as the airstream has a chance to moisten up with onsore winds. I wouldn't expect much however and the day should be a more refreshing day than today.

My Forecast: - Early change, late shower - 22C
BoM Forecast - 21C

TS cool

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#15166 - 21/09/2004 18:33 Re: South Australian and Adelaide day to day forecasting
Tornadosky Offline
Member

Registered: 31/05/2004
Posts: 1739
Loc: Adelaide
Iím going to diverge from TSís forecast here wink . I reckon that a combination of a significant amount of middle level moisture (indicated by the cloud currently in the Bight) combined with some heat at lower levels in the northerlies and the approach of the trough and front will result in scattered thundery showers in the coastal districts and some isolated lightning smile , between midnight and about 10 am tomorrow.

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#15167 - 21/09/2004 19:37 Re: South Australian and Adelaide day to day forecasting
teckert Offline
Weatherzone Moderator

Registered: 27/05/2001
Posts: 17432
Loc: NE suburbs, Adelaide, South Au...
yer it could be a slight possibility, with strikes currently showing on the tracker in the Bight...

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#15168 - 21/09/2004 20:58 Re: South Australian and Adelaide day to day forecasting
Thunderstruck Offline
Lightning man

Registered: 10/05/2001
Posts: 14800
Loc: Seaford Meadows, SA
Yes I had that feeling, noticed the cloud but put past, painful experiences into thought and said bah, not a chance...but yer if you live in the middle of the Great Australian Bight smile

Good to see you are thinking with some spontaneity tornadosky laugh laugh Keep it up! The way to go IMO.

TS cool

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#15169 - 21/09/2004 20:59 Re: South Australian and Adelaide day to day forecasting
---- Offline
Meteorological Motor Mouth

Registered: 25/11/2002
Posts: 5786
Some speccy virga and the like this evening south east of the ranges. Would have been the odd drop or 2 reaching the ground in spots. It sat trying to build in this area all day, just not enough moisture..
Towards late evening I would not have been surprised to see the odd isolated flash off the east. Had a very unstable base about it.
Made 24.9 here today and is still 19. laugh

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#15170 - 22/09/2004 08:13 Re: South Australian and Adelaide day to day forecasting
Tornadosky Offline
Member

Registered: 31/05/2004
Posts: 1739
Loc: Adelaide
730 am - change has reached Ceduna but not Port Lincoln (judging by wind direction). None of the stations reporting on the hour to BOM website have reported any rain, so my scattered thundery showers prediction is looking a little shaky but there's still two and a half hours to go yet and quite a broad cloud band. 20.6 degrees at Kent Town with a 13 k NNE wind, and 11.4 at Marree airport with a 13 k SSE wind - figure that out. Anyone see any lightning last night?

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#15171 - 22/09/2004 11:33 Re: South Australian and Adelaide day to day forecasting
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6782
Loc: Adelaide Hills.
Well this next frontal system will be somewhat of a relief and rest-bite from the 25-26 C days we've been having so far this week smile . The temperature went down to ~ 1 C on Saturdar night, it had climbed again to ~8 C for Yesterday's min, and it was warm and sunny early on yesterday (it was actually warmer outside than it was inside, which we haven't had for a long time). So at one stage the inside and outside temperatures were about the same wink . I'm not sure what others have had, but Monday and Tuesday certainly seemed to indicate the onset of something, as those were the highest temperatures we've had since last Summer eek . The weather patterns seem to have "expanded" now over the last couple of weeks, with the gap between changes increasing and the temperatures reaching new highs. I heard briefly over the news at one point that Adelaide had had its highest September temperature for so many years (40 or something), so that seemed like a good enough indication of changing patterns to me. Just looking at GFS for today (evening into night), I wouldn't expect any more than about 10-15 mm from this system - of course I'd hope for more. GASP, however, is predicting more like 15-20 mm, so maybe in between the two models is a good estimate. LAPS on the other hand seems to be predicting roughly the same as GFS, only more widespread. Which model to go for I honesty don't know, but would guess the lower end of the scale, unless, of course, the double jet has anything to do with it smile .
:cheers:

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#15172 - 22/09/2004 16:28 Re: South Australian and Adelaide day to day forecasting
Tornadosky Offline
Member

Registered: 31/05/2004
Posts: 1739
Loc: Adelaide
Great! Refuses to rain all night frown - canít even produce those few miserable thundery showers I predicted by ten am, and now, when itís past my dealine, I check the radar and thereís a broad band of rain just reaching Adelaide :rolleyes: .

Yes Nazdeck, Iíve been looking forward to ďit was actually warmer outside than it was inside, which we haven't had for a long timeĒ since last autumn smile .

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#15173 - 22/09/2004 16:40 Re: South Australian and Adelaide day to day forecasting
Tornadosky Offline
Member

Registered: 31/05/2004
Posts: 1739
Loc: Adelaide
Folks I have just been outside and Iím happy to report that yes itís real rain falling and not Ceduna rain falling! wink

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#15174 - 22/09/2004 18:05 Re: South Australian and Adelaide day to day forecasting
Thunderstruck Offline
Lightning man

Registered: 10/05/2001
Posts: 14800
Loc: Seaford Meadows, SA
LOL yes belting down here actually, see heavier embedded yellow and green section inside main rainband.

Wednesday 22/9/04

Today saw a wind change pass over at about 10am with cooler SW winds. Increasing high and middle level cloud in response to a solid upper trough passing over behind the change. Upper and mid level moisture amounts increased significantly during the day and a band of light rain with occasinal moderate bursts has been triggered from this cloud by the upper trough. No significant falls are likely as the general surface to upper dynamics of the entire system are poorly organised and are disjointed. Falls of 2-6mm are likely in most places, some inland areas may not get more than 0.2-1mm. Totals will also be light due to the higher cloud base of the rainband in question ~10,000ft with drier air below will not lead to great totals.

Thursday 23/9/04

Generally a cool day, moderate to fresh southwest winds. Cloudy especially in the morning with the likelyhood of morning drizzle patches and light showers and possible low cloud over the ranges but that should clear. Then as the high progresses eastward slowly, it should clear most shower activity later on towards the weekend.

My Forecast: - Cloudy periods, early shower or two then mainly fine: - 18C

BoM 18C

TS cool

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#15175 - 23/09/2004 08:12 Re: South Australian and Adelaide day to day forecasting
Tornadosky Offline
Member

Registered: 31/05/2004
Posts: 1739
Loc: Adelaide
730 am Thursday Payneham - looks like a fairly typical post-frontal spring morning in Adelaide, barometer rising, middle level cloud gone, thereís some low cloud south and west of Adelaide but over the city itís clear at present. Kent Town has had 4.2 mm since 9am yesterday.

Two things I found particularly interesting about the system just passed were
1. how the wheel can turn - the two previous systems were major cutoff lows with rain, showers, and in some parts storms, and I was inclined to think that the Western Australian trough would deepen to produce another cutoff low in the present case, but it did nothing of the sort
2. for a day or so as the trough approached we had mostly thin high cloud and a very dry lower atmosphere, and one could easily be forgiven for predicting that with such dry air there would be no rain band, but nevertheless in due course up went the moisture levels and in comes a rain band.

It can be a hazardous business forecasting in the spring smile .

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#15176 - 23/09/2004 15:06 Re: South Australian and Adelaide day to day forecasting
Thunderstruck Offline
Lightning man

Registered: 10/05/2001
Posts: 14800
Loc: Seaford Meadows, SA
Watching the position of the jetstreams can really aid in determining if rain will fall. Yesterday the subtropical jet and the polar jet were overlapping pretty much and in response to that upper trough really caused middle and upper level moisture to increase rapidly and cloud quikcly formed, lots of upper level divergence and due the the trigggers (jet, upper trough and sfc front of sorts) it rained nicely, 10mm in Whyalla, who would have thought.

Atm, thick thick Sc @ 3100ft is persistent and refuses to leave. Unlikely to get anywhere near 18C, didnt quite dry out as quickly as I would have hoped. Never mind, always learning.

TS cool

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#15177 - 23/09/2004 16:14 Re: South Australian and Adelaide day to day forecasting
TrenthamStormchasers Offline
Meteorological Motor Mouth

Registered: 15/04/2001
Posts: 6258
Loc: Trentham 705m
The other thing to watch is the moisture supply, and you tend to see this happening very clearly on satellite loops - there was a disctinct weakening in the moisture flow into the trough moving through the southeast that actually began a couple of days ago and at about the same time there were signs of increasing vorticity in the part of the trough over Western Australia - split in moisture feed, system to the east began to weaken, system in west strengthened.

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#15178 - 23/09/2004 17:52 Re: South Australian and Adelaide day to day forecasting
Tornadosky Offline
Member

Registered: 31/05/2004
Posts: 1739
Loc: Adelaide
Yes, my next step in learning to be a more accurate forecaster is to routinely look at the various upper level charts and the jetstream and moisture maps. Reading tea leaves is just not sufficient these days frown .

Now, it seems that forecasters are going to face some interesting challenges over the next week or so. After the present high moves east, BOM are forecasting ďmiddle level cloud will thicken ahead of the low bringing the risk of isolated showers to southern coasts on Saturday, ahead of a greater chance of patchy rain and isolated thunderstorms over western and southern agricultural districts on SundayĒ and then ďGenerally fine and warmer weather is then expected ahead of another developing low pressure system over Western Australia.Ē (BOM Notes on the Weather). A good time to start studying those charts methinks smile .

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#15179 - 23/09/2004 20:48 Re: South Australian and Adelaide day to day forecasting
Thunderstruck Offline
Lightning man

Registered: 10/05/2001
Posts: 14800
Loc: Seaford Meadows, SA
Thursday 23/9/04

Persistent Stratocumulus associated with a ridge of high pressure directing moist onshore winds resulted in an overcast day with basically no sun apart from the very early morning. Consequently, temps were down from the forecast max of 18C. max was 14.4C. Light drizzle fell from this cloud, chiefly later in the day as the temperature fell closer to the dewpoint, lowering the cloud base resulting in a thicker deck and I would expect a fair bit of drizzle to fall tonight.

Friday 24/9/04

Early drizzle patches, low cloud and fog in the hills, then clearing out to a partly cloudy day, still pretty cool with light southerly winds. The ridge of high pressure will still persist so temps will be down and cloud will lurk. Not quite as bad as today however.

My Forecast: - Cool, overcast with early drizzle clearing to a partly cloudy but fine afternoon. Max 17C

BoM Forecast - 18C

TS cool

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#15180 - 24/09/2004 07:05 Re: South Australian and Adelaide day to day forecasting
Tornadosky Offline
Member

Registered: 31/05/2004
Posts: 1739
Loc: Adelaide
Iíve just been studying the BOM forecast charts for the next four days. They are forecasting a weak low coming from the head of the Bight area to track approx south-east along the SA coastline more or less, on Saturday night and Sunday, to be centred on Bass Straight by Sunday evening. This looks like quite an uncertain situation to me - simply not possible to forecast accurately. Even a small change in the path of this low might substantially alter the weather any particular district in southern SA receives. There are plenty of situations where forecasters and computers can predict the next few daysí weather with considerable confidence. I can happily say this isnít one of them smile . If I were forecasting in this situation I would go with the most probable predictions of the computer models but indicate a high level of uncertainty and keep the forecast as general as I could.

Thereís a price to pay for the interesting weather to come though - this morning 630 am itís as TS predicted - a drifting SW airstream on the eastern side of a high (centred near Ceduna at 4 am), full low cloud cover over Adelaide and vicinity, range crest immersed in low cloud, some drizzle (ground wet at Payneham), I will agree with TS and play it safe and forecast a cloudy morning with some drizzle clearing to a mostly fine partly cloudy afternoon (I wonít mention sun in the forecast although there may be some but it might just as easily turn into anticyclonic gloom with no afternoon sun at all frown ).

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#15181 - 24/09/2004 12:20 Re: South Australian and Adelaide day to day forecasting
seaworthy Offline
Weatherzone Addict

Registered: 16/08/2004
Posts: 3672
Loc: Gawler East, SA - 102m
tornado, i know what you mean about uncertain forecasts. yesterday on the adelaide 7-day outlook they were forecasting rain, showers and the whole shabang but now its back to showers < 1mm for monday.

however, on the 7 day synoptic outlook for monday it says a band of moderate rain and storms to develop over SA along a jetstream and another low centered somewhere near Giles, WA. i hope it changes back to a positive outlook soon!

and btw TS, thanks for your explanation on the cause of the drizzle, very simple yet understandable smile

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#15182 - 24/09/2004 18:36 Re: South Australian and Adelaide day to day forecasting
Thunderstruck Offline
Lightning man

Registered: 10/05/2001
Posts: 14800
Loc: Seaford Meadows, SA
Friday 24/9/04

After overnight showers and drizzle, the low cloud gradually burnt off during the day as the onshore airstream moderated and the ridge of high pressure contracted eastward. Hence the sun was seen for a fair deal of the day. However, an upper level disturbance over WA and its associated surface low is starting to spin off high and middle level cloud and we saw some Cirrus and Cirrostratus later this afternoon with some Ac/As as well.

Saturday 25/9/04

Geneally the high cloud should clear overnight, but it will persist in patches that should increase once more later on tomorrow as that low and upper level feature pushe closer toward us. Should be a pretty nice day, light to moderate NE to N winds with a feel of warmth in the air.

My Forecast: - Fine and mild, increasing high cloud - 24C

BoM Forecast 23C.

TS cool

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