VALID 00Z SAT 16/11 - 00Z SUN 17/11 2002
ISSUED: 15/11 10:08Z
FORECASTER: HAVEN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS WRN MEDITERRANEAN SEA INTO NRN ITALY

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

GENERAL THUNDERSTORMS ARE FORECAST ACROSS BAY OF BISCAY AND AREA JUST SW OF IBERIAN PENINSULA

SYNOPSIS

N-S ORIENTATED UPPER TROUGH FROM U.K. TO IBERIAN PENINSULA IS HARDLY MOVING, WHILE UPPER RIDGE OVER BALKAN STATES REMAINS ALMOST STATIONARY. BETWEEN THESE SYSTEMS A STRONG FLOW IS MAINTAINED. LEFT-EXIT REGION OF 120-130 KT (AT 300 HPA) JETSTREAK OVER S-PART OF WRN MEDITERRANEAN AT THE BEGINNING OF THE PERIOD IS MOVING QUICKLY TO THE ALPS AND WILL ARRIVE OVER POLAND IN THE LATE EVENING. AT THE SFC...LOW OVER SE-FRANCE WILL RAPIDLY DEEPEN AT DAYTIME IN RESPONSE TO UVM ASSOCIATED WITH THE APPROACHING LEFT-EXIT REGION AND STRONG WAA NORTH OF THE ALPS. THE SFC LOW IS EXPECTED OVER E-GERMANY LATER. BAROCLINIC ZONE FROM BALTIC STATES TO ERN FRANCE TO WRN MEDITERRANEAN IS MOVING EAST AS A COLDFRONT OVER THE WRN MEDITERRANEAN AND MOV N AS WARMFRONT OVER GERMANY/POLAND.

DISCUSSION

...WRN MEDITERRANEAN SEA INTO NRN ITALY...
LOW INSTABILITY /CAPE BELOW 500J/KG / WILL BE AVAILBALE OVER THE REGION. WITH STRONG UPPER FORCING IN THE LEFT-EXIT REGION OF THE JETSTREAK...SHOWERS AND TSTMS WILL OCCUR IN THE MORNING AND EARLY AFTERNOON. STRONG SHEAR WILL BE SUFFICIENT FOR ORGANIZATION OF THE STORMS, PROBABLY INTO LINES ALONG/NEAR COLDFRONT, WITH WINDGUSTS IN EXCESS OF 50 KT POSSIBLE. WINDS WILL NOT VEER MUCH WITH HEIGHT, THEREBY DECREASING SRH AND TORNADO-POTENTIAL. LOW CAPE WILL INHIBIT THE FORMATION OF LARGE HAIL, ALTHOUGH STONES UP TO 1 OR 2 CM ARE POSSIBLE. NORTH OF THE ALPS...BOUNDARY LAYER WILL BE COOL AND SINCE DIURNAL CYCLE WILL NOT CONTRIBUTE MUCH TO DESTABILIZATION PROCESS...IT IS UNLIKELY THAT SFC BASED STORMS WILL FORM. A FEW EMBEDDED ELEVATED STORMS ARE POSSIBLE IN WAA-REGIME, BUT COVERAGE AND INTENSITY ARE TOO LOW FOR A GEN TSTM OUTLOOK. UPSLOPE FLOW OF MOIST MEDITERRANEAN AIR AND STRONG UVM ON THE SRN ALPES WILL GIVE LARGE RAINFALL AMOUNTS WITH FLOODINGS LIKELY.

...BAY OF BISCAY AND AREA JUST SW OF IBERIAN PENINSULA...
A FEW RUMBLES OF THUNDER MIGHT OCCUR AS SHOWERS DEVELOP IN A LOW TO MARGINAL UNSTABLE ATMOSPHERE IVOF THE THERMAL TROUGH. BEST CHANCES FOR TSTMS ARE NEAR SFC LOW OVER BAY OF BISCAY AND NEAR SFC TROUGH SW OF IBERIAN PENINSULA. WEAK VERTICAL SHEAR WILL MINIMIZE SEVERE THREAT.

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