CONVECTIVE FORECAST - UPDATE
VALID 08Z FRI 23/05 - 06Z SAT 24/05 2003
ISSUED: 23/05 07:54Z
FORECASTER: GROENEMEIJER
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHWESTERN RUSSIA
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL UKRAINE
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE EASTERN MEDITERRANEAN
SYNOPSIS
A WESTERLY MID/UPPER FLOW IS PRESENT OVER MUCH OF NORTHERN EUROPE. AN UPPER TROUGHOVER THE EASTERN ATLANTIC IS AMPLIFYINGEN CAUSING A BACKING OF UPPER-LEVEL FLOW OVER WESTERN EUROPE. AN UPPER-LOW IS LOCATED JUST WEST OF GREECE.
DISCUSSION
...NORTHWESTERN RUSSIA...
AIR-MASS SOUTH OF AN WEST-EAST ORIENTED FRONTAL ZONE OVER NORTHERN RUSSIA WILL BECOME UNSTABLE DURING THE DAY WITH 30HPA MLCAPE RISING TO AROUND 1000 J/KG IN PLACES. FLOW SOUTH OF THE FRONT IS QUITE HELICAL AS WELL, TIELDING A SUPERCELL POTENTIAL WITH STORMS THAT FORM DURING THE AFTERNOON. THIS ACTIVITY MAY CAUSE LARGE HAIL, STRONG WIND GUSTS AND...GIVEN STRONG LOW-LEVEL SHEAR AND QUITE LOW LCL HEIGHTS...PERHAPS A TORNADO OR TWO.
...EASTERN MEDITERRANEAN...
DESTABILISATION IS TAKING PLACE IN AN AREA OF CVA AND WARM ADVECTION TO THE EAST OF THE UPPER LOW OVER THE RISK AREA. 30HPA-MLCAPE IS EXPECTED TO RISE TO 1000-1500 THIS EVENING. WIND SHEAR WILL BE SUFFIENCT TO SUPPORT SUPERCELLS. SO DURING THE EVENING...EXPECT A FEW SEVERE STORMS OVER THE AREA TO FORM THAT ARE ACCOMPANIED BY LARGE HAIL AND DAMAGING GUSTS IS PLACES. THE STORMS WILL LIKELY CLUSTER INTO A MCS OVERNIGHT.
...UKRAINE...
AIR-MASS IN PLACE OVER THE RISK AREA IS QUITE MOIST AT LOW LEVELS. IN COMBINATION WITH STEEP LAPSE RATES, THIS WILL YIELD 30HPA MLCAPES ON THE ORDER OF 1000 - 2000 J/KG IN THE AFTRENOON. SOME STORMS WILL LIKELY DEVELOP DURING THE AFTERNOON. SINCE MID-LEVELS ARE QUITE DRY, THERE IS A THREAT OF STRONG DOWNBURSTS FORMING WITH THESE STORMS. ALSO SOME LARGE HAIL MAY ACCOMPANY THE STORMS. GIVEN THE EXPECTED LOW COVERAGE OF THE STORMS, A SLGT RISK IS NOT ISSUED ATTM.
...BALKANS...
SOLAR HEATING WILL DESTABILISE THE AIR-MASS OVER MUCH OF THE BALKANS TODAY. LATENT INSATBILITY WILL RISE TO 500-1200 J/KG 30HPA MLCAPE. 0-6 KM SHEAR OF AROUND 20-35 KNOTS WILL BE SUFFIENT FOR MULTICELLS TO DEVELOP. EXPECT A FEW REPORTS OF LARGE HAIL AND STRONG WIND GUSTS WITH THE STORMS THAT WILL DEVELOP THIS AFTERNOON.
...SOUTH-CENTRAL FRANCE...
WITHIN A FRONTAL ZONE FROM SOUTHERN FRANCE TO THE BENELUX...A WAVE WILL LIKELY DEVELOP. IN THE WARM SECTOR OF THE DEVELOPING WAVE MLCAPE IS EXPECTED TO RISE TO A FEW 100'S OF J/KG THIS AFTERNOON. SOME STORMS MAY INITIATE ALONG THE COLD FRONT OF THE WAVE. GIVEN HIGH HELICITY VALUES AHEAD OF THE FRONT, THESE STORMS WILL LIKELY BE ORGANISED AND POSSIBLY BE SUPERCELLULAR. IF SUPERCELLS FORM INDEED, THERE IS A CHANCE OF LARGE HAIL, STORNG WIND GUSTS AND POSSIBLY A TORNADO. HOWEVER, GIVEN LOW INSTABILITY AND ANTICIPATED LOW COVERAGE OF STORMS WE WILL NOT ISSUE A SLGT RISK ATTM.
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