Convective/Storm Discussion Thread 25/5/16 onwards

[Flash bang flash bang etc]

That's some tasty rain floating across the channel...

[Mapantz]

I don't really intend to start doing any maps showing where I think activity may take place, as we have the likes of Nick F on here, who does a great write up with it. But, I think Estofex have it just about right for tomorrow. I still don't expect anything exciting though.. the concern (I would have thought) is from localised flash-flooding from the slow moving  downpours. It'll be interesting to see what occurs by mid-morning!

[Flash bang flash bang etc]

Fresh strike in the channel - potents means we could see some nocturnal sparks... Fings crossed!

[Flash bang flash bang etc]

More more more! :-D

[Ben Sainsbury]

ConvectiveWeather have their forecast out!

Day 2 Convective Outlook

VALID 06:00 UTC Fri 27 May 2016 - 05:59 UTC Sat 28 May 2016

ISSUED 21:49 UTC Thu 26 May 2016

ISSUED BY: Chris

An area of humid, unstable air will drift in from the south across southern parts of Britain and Ireland between Thursday evening and through Friday. This combined with daytime heating on Friday afternoon will produce CAPE values of 500-800j/kg. The highest CAPE is expected across S/Cen England; into Wiltshire / the Salisbury plain, where we will monitor the potential for an upgrade to SLGT. Moisture may be a limiting factor with some computer models only developing isolated convection. However given the CAPE available even these isolated storms could produce a lot of lightning and some locally heavy downpours. Bulk shear remains relatively weak, so while storms will be slow moving, updrafts will be generally of the pulse variety. 

[Nick F]

My storm forecast updated to include a forecast for tomorrow now ( Day 2)

Storm & Convective Forecast

Issued 2016-05-26 17:05:48

Valid: 26/05/2016 1800z to 27/05/2016 0600z

DAY 1 & 2 CONVECTIVE FORECASTS - 26TH & 27TH MAY 2016

Full forecast here: http://www.netweather.tv/index.cgi?action=convective;sess=

Synopsis

Elongated upper low extends from west of Iberia NE toward the UK on Thursday and Friday, with a weak cyclonic SWly upper flow across southern UK. Flow veers with height from E to NEly flow at the surface. An area of increasing instability will move N out of N France this evening, bringing an isolated risk of thunderstorms across parts of S England and S Wales overnight, with further thunderstorms developing across S England and Wales during Friday.

DAY 2 CONVECTIVE FORECAST - Fri 27/05 06z to Sat 28/05

... SW/S ENGLAND, MIDLANDS, WALES and EIRE ...

Scattered showers / isolated storms ongoing first thing in the morning across S/SW UK should ease and allow recovery of the atmosphere to allow sunny spells to develop. Plume of steeper mid-level lapse rates spreading north atop of increasingly moist boundary layer across southern Britain (w/ dew points reaching 12-14C) will create an increasingly unstable atmopshere by the afternoon in the above areas - with GFS indicating 300-800 j/kg CAPE. With weak flow aloft and lack of upper forcing, wind convergence will be the main forcing mechanism for heavy showers and thunderstorms to develop in the above areas. Despite environment of weak vertical shear of 10-30 knts, clouds may attain enough height to bring a MARGINAL risk of isolated large hail, also slow storm motion will bring a risk of large rainfall totalls over a small area leading to a risk of localised flooding - the marginal risk most likely SW England/Wales. Weak winds aloft and surface convergence will also be ideal conditions for a few funnels or even brief/weak tornadoes to form with stronger updrafts.

 

Issued by: Nick Finnis

Issued by the Netweather forecast team whenever there is a risk of storms or severe convective weather, these discussion based and in depth forecasts will highlight the areas at risk and give an in depth description of the risk and the factors surrounding it.

[SteveB]

Hope this cloud breaks or it's another bust.

[NO LONGER POSTING]

Hmm sat shows quite a lot of crud across the whole of southern England I knew this would be the case this morning but to what extent was debatable..

Once the sun gets to work it should begin to break up, although it could also bubble a load more up and spoil it

Ideally you want that cloud to be getting a move on pretty quick to allow a good few hours of strong may sunshine to get in..

With very light winds today any showers that do form will be slow moving as mentioned above.

Hot spot for me would probably be the very far West coast and Bristol channel 

[Ben Sainsbury]

Certainly a lot of cloud around as said by others, however Sat24 shows this clearly fairly soon this morning so hopefully things shall spark off!

[Convective]

A few of the models are flirting with the idea of more substantial plume prospects into the end of the first week of June. GFS and ECM both showing a Biscay-originating feed of humid air as we approach the end of next week. Still a long way out in terms of model watching, but not unrealistically far out...

[Harry]

Clearing skies in London - shame its not a hotspot today really.

[Frosty hollows]

Murky and misty here. Very humid, but not sure clouds are going to clear enough this morning. Good luck storm watchers!

[dec10snow]

23 minutes ago, Harry said:

Clearing skies in London - shame its not a hotspot today really.

As I posted in our regional, same here, even thought the met forecast gives us cloudy skies until 2pm, so a good start here 

[steve86]

Lovely morning here. Blue skies a little bit of broken cloud. That's all.

[MattTarrant]

Starting to brighten up here and the south West is the hotspot today so please continue to do your work sun.

[Harry]

Not sure whether it is an error in the model, but UKMO precipiation projections generate some intense downpours across the SE/Home Counties/Midlands between 04z and 07z tomorrow.

It doesn't appear to be supported however by any other model.

Interesting.

Edited May 27, 2016 by Harry

[MattTarrant]

3 minutes ago, Harry said:

Not sure whether it is an error in the model, but UKMO precipiation projections generate some intense downpours across the SE/Home Counties/Midlands between 04z and 07z tomorrow.

It doesn't appear to be supported however by any other model.

Interesting.

I knew there was a chance of some imports in the early hours but in the day

[DAVID SNOW]

4 minutes ago, Harry said:

Not sure whether it is an error in the model, but UKMO precipiation projections generate some intense downpours across the SE/Home Counties/Midlands between 04z and 07z tomorrow.

It doesn't appear to be supported however by any other model.

Interesting.

The ECM shows it too.

[Harry]

Where do people get the ECM precipation models?

NW, Meteociel, Wetterzentrale - can't find precip charts 

 

[NO LONGER POSTING]

57 minutes ago, Harry said:

Clearing skies in London - shame its not a hotspot today really.

Edited May 27, 2016 by Surrey

[NO LONGER POSTING]

Sorry Harry mobile problems again. Euro4 backs it too, interesting we await today's runs with eagerness 

[MP-R]

Mucky start after some early morning sharp showers, although a lot of the cloud is that which I'd associate with a plume so a good sign at least. The sun is already trying to break through the cloud here and it's feeling muggy compared to yesterday so fingers crossed.

[Chris K]

Sun is starting (but struggling) to make more of an appearance here. Looking at the satellite images it looks like the stubborn cloud is starting to shift away.

I know it should not be taken literally - it always changes as showers form, but current Met Office forecast shows a cluster of heavy showers around the Devon/ W-Country /Southern Wales and S Midlands during the evening.

Looking forward to any developments - it makes a change being in the centre of multiple storm risk forecasts. However the Bristol storm shield (and the typical morning grey rubbish) can be a tough one to beat.

Edited May 27, 2016 by Chris K

[Paul]

Not sure if anyone has spotted this - but it's an impressive funnel cloud photo'd in Scotland last weekend

https://www.netweather.tv/forum/profile/1580-dougimat/?status=39193&type=status

[dec10snow]

38 minutes ago, dec10snow said:

As I posted in our regional, same here, even thought the met forecast gives us cloudy skies until 2pm, so a good start here 

Spoke too soon, clouded back over from the south...