VALID 16Z MON 21/10 - 06Z TUE 22/10 2002
ISSUED: 21/10 17:55Z
FORECASTER: VAN DER VELDE

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS W FRANCE/N SPAIN - C FRANCE

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS S FRANCE, N MEDITERRANEAN, N ITALY

GENERAL THUNDERSTORMS ARE FORECAST ACROSS W EUROPE, N MED REGION

SYNOPSIS

AT MON 12Z A 971 HPA DEEP SFC LOW SW OF IRELAND WITH WARM FRONT/OCCLUSION OVER N IRELAND, NETHERLANDS INTO CENTRAL EUROPE TRANSPORTS UNSTABLE AIR INTO MOST OF WESTERN EUROPE WITH A MAJOR COMMA CLOUD TRIGGERING CONVECTION. THE LOW MOVES TO CORNWALL AROUND 06Z TUE MORNING WITH THE WARM FRONT/OCCLUSION EXTENDING OVER DENMARK AND STAGNATING OVER S SCOTLAND. ITS ASSOCIATED WIND FIELD OVER W EUROPE BECOMES STRONGER AND SHOWERS/STORMS WITH POSSIBILITY OF SEVERE GUSTS ARE THE TYPE OF WEATHER FOR MOST OF W EUROPE ON TUESDAY.

DISCUSSION

...W FRANCE/N SPAIN - C FRANCE...
CAPE IN THE ORDER OF 400-1200 J/KG IS PRESENT OVER WESTERN FRANCE AS INDICATED BY RESPECTIVELY BREST AND BORDEAUX SOUNDINGS AT 12Z MONDAY. WITH SFC WINDS OF 15 KTS, 850 HPA WINDS OF 40 KTS, 500 HPA WINDS OF 45-50 KTS, STRONG LOW LEVEL SHEAR IS PRESENT. DIRECTIONAL AND MIDLEVEL SHEAR IS MODEST, SUGGESTING SQUALL LINES AND BOW ECHOS AS THE PRIMARY CONVECTIVE MODE. BREST SOUNDING INDICATES LOW LCL/LFC AND HIGH MOISTURE IN LOWEST 100 HPA SUGGESTING STRONG TORNADIC POTENTIAL ALONG WITH THE STRONG SHEAR IN THAT LAYER. SR HELICITIES APPEAR HIGHER IN S FRANCE/N SPAIN. SANTANDER (N SPAIN) SOUNDING SHOWS CONSIDERABLY DRYER SOUNDING, SUGGESTING A FRONT AND STRONG LIFTING MECHANISM PRESENT BETWEEN SANTANDER AND BORDEAUX. CURRENT (1530Z) IR IMAGE SHOWS CURRENT CONVECTION CLUSTERED EXTENSIVELY AS A COMMA CLOUD OVER THE SW HALF OF FRANCE, WITH DISTINCT CELLS AND SFLOCS AT THE WESTERN SIDE OF THE SYSTEM AT THE TRIGGERING LINE. THESE CELLS HAVE STRONG POTENTIAL OF SEVERE WINDS (UP TO 60 KTS) AND A FEW TORNADOS APPEAR LIKELY. HIGH CAPE/SHEAR IN SOUTHERN PORTIONS OF FRANCE AND NORTHERN SPAIN ALSO POSE THREAT OF SEVERE HAIL. OBSERVATIONS SHOW BACKED WINDS OVER THE FRENCH MASSIVE CENTRAL WHICH ALLOW HIGHER HELICITIES AND THEREFORE HIGHER CHANCE OF UPDRAFT ROTATION AND TORNADOES. LEE TROUGH CREATED BY PYRENEES ALSO GENERATED BACKED WINDS AND HIGHER HELICITIES. STORMS ARE EXPECTED TO CONTINUE INTO THE EVENING (AT 21Z APPROACHING THE ALPS) AND MOVE ACROSS CENTRAL FRANCE, WHILE CAPE WILL DECREASE, STRONG TRIGGERING REMAINS AND THE ALPS FORCE UPWARD MOTION. SHEAR HOWEVER IS INDICATED TO DECREASE TO LOW-MODERATE VALUES BY AVN MON 12Z. IN SUMMARY, A MODERATE RISK IS ISSUED WITH THE PRIMARY THREAT BEING SEVERE GUSTS, A FEW TORNADOS AND SEVERE HAIL IN THE AFTERNOON, GRANTED BY THE HIGH AREAL COVERAGE OF THE STORMS.

...S FRANCE, N MEDITERRANEAN, N ITALY...
ELEVATED STORMS, MICROBURSTS POSSIBLE BECAUSE OF DRY LOW TO MIDLEVEL ENVIRONMENTS.

...W EUROPE COASTS...
SEVERE GUSTS ARE POSSIBLE ESPECIALLY NEAR CONV. SYSTEMS... NEW COMMA CLOUDS ARE FORMING ATTM

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