CONVECTIVE FORECAST - UPDATE
VALID 10Z WED 04/06 - 06Z THU 05/06 2003
ISSUED: 04/06 10:27Z
FORECASTER: GROENEMEIJER/DAHL

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS THE BENELUX COUNTRIES AND EXTREME NORTHWESTERN GERMANY

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS AN AREA SURROUNDING THE SLGT RISK AREA INCLUDING MUCH OF DENMARK, NORTHWESTERN GERMANY, WESTERN FRANCE AND SOUTHEASTERN BRITAIN

GENERAL THUNDERSTORMS ARE FORECAST ACROSS MUCH OF WESTERN CONTINENTAL EUROPE, ITALY AND THE WESTERN BALKANS AND PARTS OF IRELAND AND NORTHERN IRELAND

SYNOPSIS

THE MAIN FEATURES ARE AN UPPER LOW WEST OF THE BRITISH ISLES AND A RIDGE OVER CENTRAL EUROPE. AN UPPER-LOW IS LOCATED OVER WESTERN RUSSIA. A MODERATELY STRONG SOUTHWESTERLY JET STREAK OVER THE BAY OF BISCAY IS EXPECTED TO PROPAGATE NORTHWARD DURING THE PERIOD. AN ASSOCIATED FRONTAL WAVE WILL MOVE NORTHWARD AS WELL.

DISCUSSION

...MODERATE RISK AREA...
WITHIN A NNE-SSW ORIENTED FRONTAL ZONE, A WAVE IS DEVELOPING, LOCATED NEAR PARIS AT 9Z. SOME WEAK CONVECTIVE ACTIVITY IS ONGOING NEAR THE TIP OF THE WAVE, BUT IN CONTRAST TO YESTERDAY'S THOUGHTS AN EXTENSIVE MCS DID NOT MANAGE TO DEVELOP. AIR MASS TO THE NORTHEAST OF THE WAVE IS VERY MOIST AT LOW LEVELS AS DEWPOINTS AROUND 20C ARE MEASURED OVER THE BENELUX COUNTRIES AND NORTHWESTERN GERMANY. MODIFYING THE 00Z DE BILT SOUNDING FOR A TEMPERATURE OF 26C AND 20C DEWPOINT, YIELDS NEAR 2000 J/KG 50HPA-MLCAPE AND ALMOST NO CIN. HOWEVER, GIVEN THAT SOME WARM AIR IS ADVECTED NORTHWESTWARD AHEAD OF THE WAVE EXPECT SOME INHIBITION TO BE PRESENT INITIALLY. THE LA VERTE-FIDAME PROFILER SHOWS 40-50 KNOT WINDS AT 500 HPA, SO THAT SHEAR IS EXPECTED TO INCREASE OVER THE BENELUX IN THE NEXT FEW HOURS. IT SEEMS LIKELY THAT CONVECTION WILL INITIATE NEAR OR JUST EAST OF THE FRONTAL ZONE OVER FRANCE, BELGIUM AND THE NETHERLANDS. THE COVERAGE OF CONVECTION WILL LIKELY INCREASE AND CLUSTER INTO AN MCS. GIVEN AMOUNT OF INSTABILITY AND SHEAR EXPECT DAMAGING GUSTS AND LARGE HAIL WITH THE ACTIVITY. HIGEST POTENTIAL OF SEVERE WEATHER WILL BE OVER THE BENELUX AND NORTHWESTERN GERMANY. GIVEN THAT LCL'S ARE GENERALLY LOW AND THERE WILL BE ABUNDANT CAPE IN THE LOWEST 3 KM, THERE IS A CHANCE OF TORNADOES AS WELL OVER THE MDT RISK AREA, IN PARTICULAR WITH MORE ISOLATED CONVECTION. THE MOST LIKELY LOCATION OF TORNADOES -THAT MAY BE SIGNIFICANT (F2 OR LARGER)- IS PROBABLY NORTH OF THE SURFACE LOW WHERE SURFACE WINDS WILL BE EASTERLY.

...SPAIN...
AS STRONG DCVA ASSOCIATED WITH AN APPROACHING ATLANTIC TROUGH OVERSPREADS THE REGION ... TSTMS SHOULD INITIATE ALONG THE COLD FRONT OVER PORTUGAL AND W SPAIN. THOUGH CAPE WILL LIKELY BE MINIMAL ... DEEP/DRY SUBCLOUD LAYER SHOULD PROMOTE STRONG DOWNWARD ACCELERATION OF THE DOWNDRAFTS ... ALONG WITH DEEP-LAYER SHEAR WILL INITIALLY BE ON THE ORDER OF 40 KNOTS ... A FEW DAMAGING WIND EVENTS SHOULD BE POSSIBLE. TSTMS MAY MERGE INTO LARGER CLUSTERS BUT WEAKENING SHEAR IS LIMITING ALLOVER SEVERE POTENTIAL.

...WESTERN BALKANS...
REF LATEST CONVECTIVE FORECAST

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