WX: UK: Severe Weather Watch – Weds 9th/Thurs 10th May 2012

UK SEVERE WEATHER WATCH #019
ISSUED: 1130UTC WEDNESDAY 9TH MAY 2012 (SM/DH/GJ/GS)
UPDATED: 2200UTC WEDNESDAY 9TH MAY 2012 (GJ)

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.

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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.

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