Stormy weather - Thursday 10th May

[Coast]

UKASF going with:

Slight

Forecaster: Dan

Last Updated: 2012-05-09 09:01:00

Valid: 2012-05-09 08:33:00 - 2012-05-09 23:59:00

Areas Affected:

SLGT: SE Wales, Midlands, E Anglia, Home Counties, West Country

Synopsis:

South of a warm front, advection of high WBPTs will move across southern Britain with potential for some slight instability.

Discussion:

Some slight instability may be generated today ahead of the next pulse of heavy rain arriving late afternoon/evening from the southwest. If any brightness can develop over the highlighted areas, there is potential for a few hundred J/kg CAPE which may allow a few shallow heavy showers or thunderstorms for a time, but it must be stressed this is a slight risk - main concern is excessive cloudiness and rather saturated profiles may hinder convection somewhat.

However, forecast soundings highlight some good directional and speed shear, with some reasonable helicity coupled with up to 14m/s LLS and 30m/s DLS, if a shower/storm should develop there is a chance of perhaps a low-topped supercell capable of producing a tornado and/or moderately-sized hail.

For now we only go for a SLGT risk due to the uncertainties and lack of confidence, but we will monitor the situation and may issue updates if necessary.

SkyWarn:

SKYWARN UK SEVERE WEATHER WATCH #019

ISSUED: 1130UTC WEDNESDAY 9TH MAY 2012 (SM/DH/GJ/GS)

SKYWARN UK HAS ISSUED A SEVERE WEATHER WATCH FOR THE FOLLOWING REGIONS: WALES ENGLAND SCOTLAND

IN EFFECT FROM 1130UTC WEDNESDAY 9TH UNTIL 2359UTC THURSDAY 10TH MAY 2012

STRONG WARM AIR ADVECTION UNDER THE DIVERGENT NOSE OF A DEEP JETSTREAM, WITH CYLOGENESIS PROVIDING FURTHER DEEP MOISTURE CONVERGENCE AND INSTABILITY

THERE IS A POSSIBILITY OF SEVERE WEATHER AFFECTING THE INDICATED REGIONS IN THE TIME PERIOD SPECIFIED. THREATS WITHIN THIS WATCH INCLUDE, BUT ARE NOT LIMITED TO: HEAVY RAIN...FLOODING...STRONG GUSTS...FUNNELS / WEAK TORNADOES

DISCUSSION:

THERE IS STRONG MODEL AND PARTNER AGENCY CONFIDENCE ON THE POSSIBILITY OF A NUMBER OF SEVERE WEATHER RISKS THROUGH WED AND THUR, DETAILED SEPARATELY WITHIN THIS WATCH. IN THE COMING HOURS, A WARM FRONT PUSHES NORTHEAST ACROSS THE WATCH AREAS WITH CYCLOGENESIS TO THE SOUTHWEST PROVIDING SOME VEERING OF THE LOW LEVEL WINDS AHEAD OF IT. A ZONE OF CONVERGENCE MAY BECOME THE FOCUS FOR SPORADIC EMBEDDED CONVECTION, WITH AREAS BETWEEN WALES AND EASTERN ENGLAND POSSIBLY AT RISK OF MORE ORGANISED ORGANISED CONVECTION GIVEN THE DIRECTIONAL SHEAR PROFILE IN THE LOW TO MID LEVELS AND STRENGTHENING DLS WITH THE ONCOMING JET AND FRONTAL WAVE ALOFT. BRIEF SUPERCELL CHARACTERISTICS CANNOT BE RULED OUT, THOUGH THIS RISK IS MARGINAL.

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

DURING THURSDAY AFTERNOON, THERE IS POTENTIAL FOR STRONG CONVECTIVE INITIATION ACROSS PARTS OF NORTHEAST ENGLAND IN A HIGHLY SHEARED ENVIRONMENT. HEAVY GENERAL PRECIPITATION WITH POSSIBLE CONVECTIVE ELEMENTS WILL LINGER OVER SCOTLAND DURING THE DAY, POSSIBLY ACCUMULATING AS MUCH AS 30-40MM IN CENTRAL AREAS. FLOODING IS ALSO POSSIBLE HERE THOUGH LESS LIKELY.

[Coast]

I feel tired for an unexplained reason...

Yep, The Voice does that to me too.......

[Mapantz]

94% humidity here, the highest humidity level in a long long time!

I find that interesting, the humidity has hit the 90's every day here for the last 24 days.

Edited May 9, 2012 by Mapantz

[Eskimo]

I find that interesting, the humidity has hit the 90's every day here for the last 24 days.

We are on different sides of the country, you are more prone to the onslaught of humid south westerlies.

[Aaron]

Dew Point is almost above 10C here, which would be the first time since March when it reached 10.5C.. doesn't feel muggy though, since it's cool bordering chilly.

[Mapantz]

We are on different sides of the country, you are more prone to the onslaught of humid south westerlies.

It's still strange.

Have a peek at this, http://www.gardiners.info/graphs.html Manuden, not too far from you.

The outside humidity graph shows it in the 80's and 90's quite a lot.

12.5°C dew point here. Definitely a muggy feel to it. Looking forward to some heavy rain though.

Edited May 9, 2012 by Mapantz

[Coast]

Dewpoints already creeping up:

http://www.netweathe...rrent;type=maxd

[Eskimo]

Dew points are 13.7C here, muggy muggy muggy.

[Snowangel-MK]

Same here...mild and moist

Temperature 15.8 °C

Dew Point 14 °C

Humidity 94%

[Harry]

Same here...mild and moist

Temperature 15.8 °C

Dew Point 14 °C

Humidity 94%

Sorry...always tickles me when anything is described as "moist"

I always stick with humid, oppressive or muggy hehe!

Speaking of which, this humidity is really ramping up now!!! Thoroughly expecting the heavens to give way tonight!!

[gottolovethisweather]

Here she comes, Bridgette from Biscay.

Currently 13.7c here after a max of 14.2c @ 1420BST, DP currently 13.1c, RH 96% and rising slowly barometer reading of 1008.1hpa.

No sferics detected yet but good luck all, who knows what might come off.

Regards

gottolovethisweather

[Eskimo]

Sorry...always tickles me when anything is described as "moist"

I always stick with humid, oppressive or muggy hehe!

Speaking of which, this humidity is really ramping up now!!! Thoroughly expecting the heavens to give way tonight!!

Don't get me started lol

[Coast]

good luck all, who knows what might come off.

I'm reasonably confident of rain, lots and lots of rain!!!!

[Snowangel-MK]

Here she comes, Bridgette from Biscay.

............, who knows what might come off.

Regards

gottolovethisweather

*tsk* is she another one of your 'models'

[gottolovethisweather]

I'm reasonably confident of rain, lots and lots of rain!!!!

I think you are onto something there for sure, where will be the highest total and how much?

I'd hazard a guess at Brize Norton and a 38mm (0900 to 0900) rainfall total. Of course, I am cheating slightly as the total would include today's rainfall thus far.

Cheers

gottolovethisweather

Edited May 9, 2012 by gottolovethisweather

[Aaron]

NAE is forecasting the highest totals to be in south west Scotland..

[Snowangel-MK]

Sorry...always tickles me when anything is described as "moist"

Really Harry.... I'm only taking about the weather

[gottolovethisweather]

*tsk* is she another one of your 'models'

She's French and I'll say no more other than my area could be very moist, come the morning.

[Aaron]

Actually NAE Is now forecast the highest totals to be in NW England

[gottolovethisweather]

Actually NAE Is now forecast the highest totals to be in NW England

Let's play place your bets......

[A.J]

Could have sworn this thread was about a storm chase and tomorrow's convective potential?.......

[gottolovethisweather]

Could have sworn this thread was about a storm chase and tomorrow's convective potential?.......

??? Is there another thread AJ? I'll try not to derail this thread any further...............

Edited May 9, 2012 by gottolovethisweather

[Supacell]

Rain is a certainty, but what about thunderstorms, lightning, tornadoes, supercells?

[Mapantz]

Here she comes, Bridgette from Biscay.

Currently 13.7c here after a max of 14.2c @ 1420BST, DP currently 13.1c, RH 96% and rising slowly barometer reading of 1008.1hpa.

No sferics detected yet but good luck all, who knows what might come off.

Regards

gottolovethisweather

It looks like it's scooting up at a more acute angle than that. The heavier stuff looks like going towards the IoW and East.

[Harry]

Really Harry.... I'm only taking about the weather

The tongue of warmth is really depicted well there in that graphic! Often leads to an exciting and quite electric atmosphere with pulsating bursts of energy once the moisture has been knocked out of the way......I can go on but I won't

Could have sworn this thread was about a storm chase and tomorrow's convective potential?.......

Tomorrow's potential will be determined by how tonight pan's out...so both IMO are significantly interconnected and relevant within this thread

When the NAE charts are chopping about, which are normally one of the most reliable in the short time frame, it usually means a complex setup which could go either way.

Really wouldn't want to second guess anything at the moment to be honest!