VALID 00Z MON 21/10 - 00Z TUE 22/10 2002
ISSUED: 20/10 18:37Z
FORECASTER: HAVEN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS LARGE PARTS OF WRN AND SWRN EUROPE

GENERAL THUNDERSTORMS ARE FORECAST ACROSS THE AREA SURROUNDING THE SLGT RISK AREA

GENERAL THUNDERSTORMS ARE FORECAST ACROSS NORWEGIAN BASIN AND SURROUNDING LAND AREAS

SYNOPSIS

SOUTHWESTERLY JETSTREAM OVER SOUTHWESTERN EUROPE WITH SEVERAL EMBEDDED VORTICITY MAXIMA. SYNOPTIC SCALE STORM SYSTEM SOUTHWEST OF IRELAND IS SLOWLY MOVING EAST-NORTHEAST. ASSOCIATED WARMFRONT AT 00Z PROGGED OVER THE ENGLISH CHANNEL AND NORTHERN FRANCE IS MOVING ACROSS BENELUX AND GERMANY IN THE MORNING AND IS FOLOWED BY A COLDFRONT, AT 00Z FROM SOUTHEAST-IRELAND TO NORMANDY TO CENTRAL SPAIN. 24 HOURS LATER IT IS EXPECTED AS AN OCCLUSION FROM NORTH-IRELAND TO DENMARK TO CENTRAL POLAND, THEN AS A COLDFRONT CURVING TOWARDS THE WESTERN ALPES. BEHIND THIS FRONTAL SYSTEM SEVERAL TROUGHS WILL MOVE ACROSS WESTERN EUROPE IN A STRONG SOUTHWESTERLY AIRFOW OF POLAR AIR.

DISCUSSION

...WESTERN EUROPE - NEAR WARMFRONT...
VERY STRONG WARM ADVECTION OVER WESTERN EUROPE AS SUBTROPICAL AIR BEING ADVECTED NNE-WARD. THIS CAN BE SEEN IN SEVERAL 12Z SOUNDINGS BY THE STRONGLY VEERING WINDPROFILES WITH HEIGHT OVER SOUTHERN U.K. AND WESTERN FRANCE. 12Z SOUNDINGS OF BORDEAUX AND BREST ALSO SHOW VERY STEEP MIDLEVEL LAPSE RATES OF 9 K/KM. BOUNDARY LAYER SEEMS TOO COOL TO SUPPORT SURFACE-BASED STORMS HOWEVER. IF ELEVATED STORMS SHOULD FORM IN THE WAA-REGIME OVER SRN U.K./BENELUX/GERMANY...SHEAR IN THE STORM BEARING LAYER WILL BE UNSUFFICIENT FOR ORGANIZED STRONG STORMS, ALTHOUGH A DRY MICROBURST CANNOT BE RULED OUT.

...WESTERN AND SOUTHWESTERN EUROPE - NEAR AND BEHIND COLDFRONT...
400-800 J/KG SBCAPE WILL BE AVAILABLE NEAR AND BEHIND COLDFRONT. STRONG UVM AND SFC CONVERGENCE NEAR COLDFRONT AND SFC TROUGHS WILL ALLOW SHOWERS AND TSTMS TO DEVELOP. DEEP LAYER SHEAR WILL BE SUFFICIENT FOR ORGANIZED STRONG TO SEVERE TSTMS OVER A LARGE AREA, ALTHOUGH SHEAR WILL BE LOWER OVER SEA AREAS DUE TO STRONG SFC WINDS. PRIMARY THREAT WILL BE DAMAGING WINDS AND LOCALLY SOME (MARGINAL) LARGE HAIL. CONVECTIVE MODE IS EXPECTED TO BECOME MULTICELLS, PROBABLY ARRANGED IN LINES. WINDS WILL BE ALMOST UNIDIRECTIONAL WITH HEIGHT, SO SUPERCELL THREAT IS QUITE LOW. IF A STORM COULD MANAGE IT TO BECOME RIGHTMOVING...TORNADO THREAT IS ENHANCED. GREATEST /BUT STILL QUITE LOW/ THREAT FOR TORNADOES IS OVER NRN IBERIAN PENINSULA AND FRANCE WHERE 0-3KM SRH OVER 300 M2S-2 ARE CALCULATED BY AVN MODEL.

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