Upcoming Convective / Storm Risk Discussion - w/c 12th May

[Lauren]

Just had a very short but intense hail/rain shower in Medway.

[DAVID SNOW]

Well  that was fun, thunder lightning and garden pea size hail

[Coast]

Well  that was fun, thunder lightning and garden pea size hail

 

Looks like there are one or two reports of thunder in that area. Seems to be getting going nice and early

Edited May 23, 2013 by Coast

[Richie V]

Massive angry skies here, I hear distant thunder. It's only 4.2C after the last shower and the suns out!

[Nick F]

Storm & Convective Forecast - Issued 23/05/2013 11:00

 

Valid: 23/05/2013 11:00 - 24/05/2013 00:00

Headline: ... THERE IS A RISK OF THUNDERSTORMS FORECAST ...



Synopsis
An upper low centred over the south North Sea this morning will be stationary through much of the day, whilst a fairly deep surface low over southern Norway slides SW towards eastern England by tonight on the western side of this upper low. A strong, cold and unstable northerly flow will affect the British Isles today.

... CENTRAL, SOUTHERN & EASTERN ENGLAND ...

Despite rather meager CAPE and positive LI values shown by the GFS model over recent runs for today, upper trough moving SE over Sern Britain will produce unseasonably cold 500mb temps (as low as -35C) aloft - which will generate steep lapse rates, particularly given any surface heating in the strong late May sunshine. Although rapid infill of cloud will hamper widespread storm development today, limited sunny spells may allow a few scattered thunderstorms to develop in the above areas where moisture is greatest and lapse rates steepest. Though isolated lightning is possible anywhere in the UK. Any heavy shower or thunderstorm will be capable of producing hail along with locally torrential downpours with a risk of flooding. Thunderstorm risk should disappear after dark.

 

 

Issued by: Nick F - Forecaster for Netweather

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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.

Edited May 23, 2013 by Nick F

[AWD]

Frequent squally rain showers here currently.

Not much sun to allow for any surface heating to develop and cloud tops to rise. It's blooming cold though.

[Richie V]

Proper mental hail now, everything white.

 

EDIT: It's like friggin December out there, temp just 1.4C in the hail downburst

Edited May 23, 2013 by Richie V

[VillagePlank]

Yes, and in that respect the index is useless. If we take the high values as a good indicator of potential storm severity, then the likelihood is that any storm that develops either today or tomorrow will be severe, right? Not so. CAPE is marginal, moisture low, and vertical wind shear weak- those are the three main factors to focus on for determining the likelihood of severe convective weather occuring.

 

Well, I'm no expert, so I'm happy to take advice from just about anyone. My reason for using TTs is: http://www.skystef.be/calculator-totaltotalsindex.htm But as you say, if I put in 850hPa = -4C, 850hPa DP = -6.81, and 500hPa = -34C, I get TT=57, which is what GFS forecasts for Rochester, which, given the description, provided, seems unlikely.

[Coast]

if I put in 850hPa = -4C, 850hPa DP = -6.81, and 500hPa = -34C, I get TT=57, which is what GFS forecasts for Rochester, which, given the description, provided, seems unlikely.

 

NMM says not far off that later?

 

 

[Nick F]

Atd showing lightning over Kent, E Sussex, Suffolk, Cambs, Leicestershire and Lincs in the last hour.

[Coast]

Atd showing lightning over Kent, E Sussex, Suffolk, Cambs, Leicestershire and Lincs in the last hour.

 

Lets hope it hangs about for a while, so I can drive towards it after work.

[dave48]

Slightly more thunderstorm activity than I thought there might be today so far...

 

They often get a hard time but in this case, full credit to the met office/bbc forecast that has been mentioning this for several days.

 

Had a brief heavy rain/hail shower here in Tunbridge Wells this morning. Some lightning about this area, the closest being about 10 miles to our south and east.

[Nick F]

Slightly more thunderstorm activity than I thought there might be today so far...

 

They often get a hard time but in this case, full credit to the met office/bbc forecast that has been mentioning this for several days.

 

 

 

Yes, as the GFS convective parameter charts don't do justice to the convective threat today - so always worth taking note of the metoffice forecasts if they mention thunder, even if GFS doesn't look keen on the idea. Given how unusually cold the uppers are today (-35C at 500mb), along with some brief sunny spells and low pressure - it's the recipe for some weak storms at this time of year.

Edited May 23, 2013 by Nick F

[Alex95]

Heavy hail shower here at 10:30 this morning, but since then I've been watching the showers slide past to my west. Very gusty winds when a shower gets nearby though!

[Eye to the sky]

Frequent heavy squally showers here with hail mixed in with the rain.Some pretty dramatic clouds to my Nw but most are drifting down to my east.Pretty sure I heard two rumbles of Thunder around an hour ago but nothing since.Most of the action seems to be just east of here.

[VillagePlank]

Lots of hails showers observed here in Rochester with gusty winds inside showers.

[Evening thunder]

Just had 2 surprise gunshot type claps of thunder here, quite loud and short.

[Ben Sainsbury]

Didn't expect 1 thing today and we have had 2 torrential hail showers, 1 at 1:30pm which had a nice structure on it and the other about 10 minutes ago!

[Karl83]

Didn't expect 1 thing today and we have had 2 torrential hail showers, 1 at 1:30pm which had a nice structure on it and the other about 10 minutes ago!

Where are you in Bristol? Add it to your profile mate.

[Coast]

All the right clouds, just nothing coming out of them yet......

[AWD]

Decent heavy hail shower has just passed through Swindon.

Nice, pea sized hail turning the ground temporarily white. Sun was shining at the same time too.

[Convective]

Can see next weeks potential starting to fade away to more consecutive 'thundery showers with the odd thunderstorm' days...

[Geordiesnow]

Heavy hail shower here at 10:30 this morning, but since then I've been watching the showers slide past to my west. Very gusty winds when a shower gets nearby though!

 

I'm further East than you and I had some hail showers around here today, nothing deadly heavy apart from one at the time you mentioned and one around 2ish but interesting nonetheless. You must of been unlucky(or lucky!) to avoided the showers. 

[Arnie Pie]

Shot between 4 - 6.45pm over Birmingham (through the scaffold poles)

No T& L but

swaths of hail & rain (Virga) from todays cells travelling down the spine of the country

http://www.netweather.tv/index.cgi?action=news;storyid=5177;sess=

 

http://youtu.be/1Gos6SF4rs4

Edited May 23, 2013 by Arnie Pie

[nitro_deluxe]

Close but no cigar today - fair few fleeting showers some with hail, pretty gusty at times too. Tomorrow may well bring the goods for some, so the April showers continue...just need a bit more oomph! For my liking.