VALID 18Z SUN 13/10 - 00Z SUN 13/10 2002
ISSUED: SUN 13/10 17:01Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTWESTERN FRANCE AND THE WESTERN BENELUX

GENERAL THUNDERSTORMS ARE FORECAST ACROSS ACROSS THE EASTERN BALKAN COUNTRIES

SYNOPSIS

LONG-WAVE TROUGH OVER EAST/CENTRAL EUROPE TOWARDS WESTERN BALKAN REGIONS WILL LIFT OUT AND CONTINUE SLOW EASTWARD MOTION. A JET STREAK ATTM REACHING THE W EUROPEAN COAST...IS EXPECTED TO CONTINUE PROPAGATING EASTWARDS. SMALL SURFACE CYCLONE HAS DEVELOPED IN LEFT EXIT REGION... NOW OVER CHANNEL REGION. RATHER EXTENSIVE FILLING SFC LOW IS ASSOCIATED WITH THE MEDITERRANEAN UPPER TROUGH. ASSOCIATED COLD FRONT IS NOW OVER THE AEGEAN SEA.

DISCUSSION

...SOUTHEASTERN ENGLAND...NORTHWESTERN FRANCE...WESTERN BENELUX...
SUB-SYNOPTIC SCALE LOW HAS FORMED IN THE CHANNEL REGION. GUSTS OF 60 KTS HAVE BEEN REPORTED ALONG THE FRENCH COAST. AN ANALYSIS BASED ON BUOY DATA ESTIMATES CENTRAL SURFACE PRESSURE OF 989 HPA. PROFILERS IN SOUTHEASTERN BRITAIN SHOW STILL STRONGLY VEERING WINDS WITH HEIGHT AHEAD OF SYSTEM, SHOWING THAT SYSTEM IS STILL BAROCLINIC AND SOME FUTHER DEVELOPMENT CAN BE EXPECTED. THIS IS CONFIRMED BY KNMI-HIRLAM 1312 AND GME 1312 MODEL RUNS, THAT DEEPEN THE SYSTEM ANOTHER FEW HPA. IT IS EXPECTED THAT THE SYSTEM WILL CONTINUE ITS NORTHEASTWARD MOVEMENT. EXPECT WIND GUSTS OF UP TO 65 KTS NEAR COASTS TO 55 KTS FURTHER INLAND. THE CAMBORNE 03808 12 SOUNDING SHOWS ABOUT 300 J/KG OF CAPE IN A NEARLY UNCAPPED ATMOSPHERE. IF CONVECTIVE ACTIVITY MANAGES TO DEVELOP UNDER DRY UPPER-AIR INTRUSION ENHANCED VERTICAL MOMENTUM FLUXES WILL OCCUR AND HIGHER GUSTS MAY BE POSSIBLE.

...SOUTHERN BALKANS...AEGEAN SEA...PARTS OF THE CENTRAL MEDITERRANEAN...
SCATTERED TSTMS PERSISTING BENEATH UPPER THERMAL TROUGH OVER THE S-CNTRL MEDITERRANEAN SEA AND ACROSS GREECE/ADJACENT STATES. ADDITIONAL TSTMS HAVE DEVELOPED OVER THE AEGEAN SEA AND E GREECE ALONG THE COLD FRONT. SOUNDINGS IN THE PREFRONTAL AS WELL AS IN THE POSTFRONTAL ENVIRONMENT INDICATE NEUTRAL TO WEAKLY UNSTABLE LAPSE RATES. HOWEVER...DEEP-LAYER SHEAR ON THE ORDER OF 40 TO 50 KNOTS IS PRESENT AT THE PERIPHERY OF THE UPPER TROUGH. THIS SUGGESTS THAT A FEW STORMS MAY BECOME MULTICELLULAR...APT TO PRODUCE ISOLATED MARGINALLY SEVERE HAIL AND A FEW STRONG WIND GUSTS. ALSO...AN ISOLATED MESOCYCLONE OR TWO MAY FORM IF LOW-LEVEL WIND FIELD CAN LOCALLY BE ENHANCED BY OROGRAPHY. IN THIS CASE...QUITE LOW LCL HEIGTS SUGGEST ENHANCED LIKELYHOOD LOW-LEVEL ROTATION WITH ANY SUPERCELL. THUS...AN ISOLATED TORNADO EVENT OR TWO MAY OCCUR. BEST CHANCES FOR THIS SCENARIO WILL BE E OF THE COLD FRONT WHERE WEAK LARGE-SCALE LOW-LEVEL VEERING IS PRESENT ALREADY. HOWEVER...ALLOVER SEVERE THREAT IS TOO LOW TO WARRENT A SLIGHT RISK ATTM.

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