Storm Risk Discussion Part 3

[Snowyowl9]

Thunder is not out of the question under HP,not today as the air is too dry.

Anyway a small trough is shown under with a warm east/NE-ly monday,a few showers shown.

http://91.121.93.17/pics/brack1a.gif

http://91.121.93.17/pics/Rtavn604.png

[dogs32]

slight chance for Monday

you can get a Isolated TS under High pressure.seen it throughout my 72 yrs on and off...though not that common they can happen

Thunderstorms can form in High Pressure, and a lot of people to misconcieve that notion. On every pressure system there is a positive and a negative side. These positive and negatives are vorticies values, and they determine basically the direction particles in the air are spinning.

Edited May 31, 2009 by dogs32

[Stuart]

Storm Forecast Issued: 2009-05-31 11:47:00

Valid: 2009-06-01 00:00:00 - 2009-06-01 23:59:00

Regions Affected

Central Southern England & West Country ( SW England, C & S Wales, W & S Midlands, Highlands and Grampians are all included in the WATCH )

Synopsis

A warm and humid airmass covers most of the UK on Monday under a large High pressure system centred over Scotland. Very high temperatures (mid-20`s expected) combined with high humidity and local sea breezes are expected to develop isolated thunderstorms across the Hampshire Downs/Salisbury Plain area during the afternoon, which are then forecast to drift slowly westwards on light easterly winds. Any convection that does take place may benefit from the high CAPE values on offer, with up to 1400J/kg available. Any storms that do develop pose a risk of a funnel. Scattered orographic showers are forecast to develop over the northern mountains of Scotland. Due to the less favourable environment, these showers are not expected to be thundery. Any showers that do develop are expected to decay rapidly during the evening.

http://ukasf.co.uk/module-Storm/mode-forecast/id-207/

[A.J]

Thanks Stuart, that ties in quite nicely with the various models.....Salisbury plain, always a good breeding ground for storms....

[Stuart]

Good luck ones down south

Edited May 31, 2009 by Stuart

[Harry]

There's the Kesurex gap! Storms to W, S and far E - sunny, dry and humid here.

Enjoy all should anything appear.

[Harry]

Looking at the GFS runs, the next plume event looks possible around 11th June onwards - too long to wait lol

[maidstone weather]

There's the Kesurex gap! Storms to W, S and far E - sunny, dry and humid here.

Enjoy all should anything appear.

haha yeah i see what you mean ah well we're used to it by now B)

a couple more sunny and warm-ish days before it cools down a little

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

I would like to see a storm here, but i dont think the chances are that high!

dp of 13.6C.

[*AL*]

B) Well hopefully it will be Swindons 'turn' for a storm, nothing at all here to talk about as yet.Fingers crossed again!

[Andy Bown]

Thanks Stuart, that ties in quite nicely with the various models.....Salisbury plain, always a good breeding ground for storms.... B)

Yes, and this time those of us to the W/NW of the Plain (Andy puts hand up) may benefit. It would seem that this shower risk is the only chance of rain all week.

I'll be watching the sky closely all day tomorrow, but don't expect development to occur until mid-afternoon or more likely late afternnoon into the evening.

[Devon-Nelly]

Here's hoping they drift there way over here , although its not been very humid at all today, RH was 44% during the hottest part of the day its only 55% now.

This forecast reminds me of early May 2006 when some quite severe storms sparked off on the M4 corridor and drifted eastwards during the evening into the Bristol Area/ North Devon and South Wales. Temps that day were in the mid 20's. But it wasnt forecast to my memory.

[StormChaseUK]

Here's hoping they drift there way over here , although its not been very humid at all today, RH was 44% during the hottest part of the day its only 55% now.

This forecast reminds me of early May 2006 when some quite severe storms sparked off on the M4 corridor and drifted eastwards during the evening into the Bristol Area/ North Devon and South Wales. Temps that day were in the mid 20's. But it wasnt forecast to my memory.

You mean this one :lol:

[Nick F]

Looks like there could be a few sharp showers and even an isolated t-storm over central-S and SW England, probably Wilts, Hants, Dorset and Devon most likely to see something.

After that, looks a bit of a storm drought developing ... oh well got my fix for a while

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

Looks like there could be a few sharp showers and even an isolated t-storm over central-S and SW England, probably Wilts, Hants, Dorset and Devon most likely to see something.

When will that happen? I cant see anything on the radar.

[maidstone weather]

When will that happen? I cant see anything on the radar.

tomorrow afternoon :lol:

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

tomorrow afternoon :lol: :unsure:

That explains it :lol:

[Coast]

Looks like there could be a few sharp showers and even an isolated t-storm over central-S and SW England, probably Wilts, Hants, Dorset and Devon most likely to see something.

Yep, keeping my eye on this one Nick!

Storm Forecast

Valid: Mon 01 Jun 2009 06:00 to Tue 02 Jun 2009 06:00 UTC

Issued: Sun 31 May 2009 22:27

Forecaster: SCHLENCZEK

A level 1 was issued for S Belarus and N-central Ukraine mainly for large hail.

A level 1 was issued for S-central Italy and the S Dinaric Moutains mainly for excessive rain and large hail.

SYNOPSIS

On Monday, severe weather should only be possible in the vicinity of an upper cut-off low over SE Poland / Slovak. Rep. Initially, the trough axis is W-E oriented but this will change through the period as a longwave trough over N Scandinavia will dig southward. An upper jet streak circles around the low pressure system with a maximum of 25 m/s at 500 hPa near Sicily. In this moderately warm airmass around the upper low, MLCAPE will stay below 1000 J/kg in most places. At the eastern flank of the low, very warm air is advected northward into southern Russia.

DISCUSSION

...N France, Belgium, SW-central Germany...

Ahead of the low pressure system, diurnal heating may lead to about 500 - 1500 J/kg CAPE which should result in briefly organized multicells and pulsating storms as DLS will stay below 10 m/s. A few storms should nevertheless be capable of producing isolated large hail and severe wind gusts but overall threat will remain rather low. Rich BL moisture and a slow expected storm motion may lead to heavy rainfall which will locally result in flash floods. According to the latest runs of GFS and WRF, storms should develop over central Germany and the eastern parts of France / Belgium in the late morning / early afternoon and dissipate over C France in the late evening / night hours. The coverage of severe thunderstorms should be too low for a level 1.

Storm Forecast Issued: 2009-05-31 11:47:00

Valid: 2009-06-01 00:00:00 - 2009-06-01 23:59:00

Regions Affected

Central Southern England & West Country ( SW England, C & S Wales, W & S Midlands, Highlands and Grampians are all included in the WATCH )

Synopsis

A warm and humid airmass covers most of the UK on Monday under a large High pressure system centred over Scotland. Very high temperatures (mid-20`s expected) combined with high humidity and local sea breezes are expected to develop isolated thunderstorms across the Hampshire Downs/Salisbury Plain area during the afternoon, which are then forecast to drift slowly westwards on light easterly winds. Any convection that does take place may benefit from the high CAPE values on offer, with up to 1400J/kg available. Any storms that do develop pose a risk of a funnel. Scattered orographic showers are forecast to develop over the northern mountains of Scotland. Due to the less favourable environment, these showers are not expected to be thundery. Any showers that do develop are expected to decay rapidly during the evening.

Edited June 1, 2009 by Coast

[Lynxus]

Interesting.

You never know, with all this heat we could see something.

Will have to wait until this arvo before really looking.

[Ross B]

Convection appears to be kicking off just over the moor's to my north. Already! (A few convective Cumulus so far)

I didn't think anything would happen here but it seems the temperature today will be higher than the 24c forecast. :o

[dogs32]

some nice cloud bubbling up south of here

cant see any rotation yet :o

Edited June 1, 2009 by dogs32

[Harry]

I notice estofex have blanketed all of the SE within their watch also :o

Not expecting much though to be honest - feels a bit more humid than yesterday, but that's about it. Unless there is a surge in humidity within the next hour or two, I think at most we'll get is a light shower, if anything.

It was blue skies earlier though a fair few fair weather cumulus have formed recently, one or two of them beginning to look 'ambitious'.

Will keep an eye out.

EDIT - Hmm, pardon my hastiness in posting - I didnt realise the CAPE and storm risk maps had changed to include the London area for mid afternoon time. Well definitely be keeping an eye in that case (though still not hopeful tbh)

Edited June 1, 2009 by Harry

[VillagePlank]

Castellenus (sp?) appearing, so convection occuring. Very disparate, and to my West.

Wasn't really expecting much from this spell of warm weather, to be honest, especially after the Beeb forecast, this morning, but still there's some MLCAPE, LI's of -1.Looks like a very narrow window, to me, today, possibly about 16z.

And from this, and using the VP-Stormcard(tm - lol), I would say that thunderstorms for this location are unlikely, but if they should occur they will be moderately severe, with an outside chance of an MCS.

Incidentally, K-Index is a relatively poor cousin of LI, and the two should be used together. An LI of less than -3 is good for storms - at least it gives us four numerical values CAPE, LI, K, and TT to play with

(EDIT: If anyone wants to modify the storm-card, then please let me know - also, let me know if you find it useful! - it was highly modified after it's disastrous forecast effort the other night, so it's certainly a work in progress! Also, any other values you think should be in there ....)

Edited June 1, 2009 by VillagePlank

[Harry]

Some big cumulus clouds going up here now!

Think here though we are only the breeding ground - any initiation (if at all) will be further west me thinks.

[VillagePlank]

Updated it already ...

It should be read from left to right such that, for today, reading off the Skew-T chart(k=27, tt=51) The english language forecast should be ...

There is a moderate to low chance of convection, but if it occurs there is a low chance of thunderstorms occuring. Where convective showers occur, precipitation will be moderately intense with a low chance of lightening.

What d'ya reckon?

Edited June 1, 2009 by VillagePlank