VALID 00Z SUN 27/10 - 00Z MON 28/10 2002
ISSUED: 26/10 12:14Z
FORECASTER: GROENEMEIJER

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN ENGLAND, THE BENELUX COUNTRIES, NORTHERN FRANCE, NORTHERN AND CENTRAL GERMANY WESTERN POLAND AND THE WESTERN CZECH REPUBLIC

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SURROUNDING THE MODERATE RISK AREA

GENERAL THUNDERSTORMS ARE FORECAST ACROSS MUCH OF THE NORWEGIAN SEA, SOUTHERN SCANDINAVIA, NORTHWESTERN CONTINENTAL EUROPE, THE BRITISH ISLES AND ADJACENT PARTS OF THE ATLANTIC.

SYNOPSIS

A STRONG ZONAL JET IS PRESENT OVER WESTERN EUROPE. A BAROCLINIC WAVE IS RAPIDLY EVOLVING INTO A INTENSE LOW PRESSURE AREA NEAR 50N 20W. IN STABILITY IN POLAR AIR-MASS TO THE SOUTHWEST AND WEST OF THIS SYSTEM WILL.

DISCUSSION

...SOUTHERN IRELAND, SOUTHERN ENGLAND, THE BENELUX COUNTRIES, FRANCE, NORTHERN AND CENTRAL GERMANY, WESTERN CZECH REPUBLIC, WESTERN POLAND....
AFOREMENTIONED INTENSE SURFACE CYCLONE WILL TRACK EASTWARD. STRONG WIND FIELD WILL INDUCE VERY HIGH WIND SHEAR /NEAR 50 KNOTS/ IN THE 0-1 KM LAYER. INSTABILITY WILL BE HIGH ENOUGH FOR THE DEVELOPMENT OF SEVERE THUNDERSTORMS. HIGHEST GUSTS /PROBABLY ON THE ORDER OF 80 KNOTS/ ARE EXPECTED ON LINEAR SYSTEMS ON PASSAGE OF SURFACE TROUGH/BACK-BENT OCCLUSION. VERY HIGH SHEAR VALUES IN COMBINATION WITH LINEAR FORCING WILL LEAD TO LINEAR CONVECTIVE SYSTEMS. SOME EMBEDDED ROTATING UPDRAFTS MAY DEVELOP GIVEN EXTREME LOW-LEVEL SHEAR THAT CAN EASILY YIELD HIGHLY HELICAL INFLOWS IN REACTION TO SMALL FLOW PERTURBATIONS (BY CONVECTION OR OROGRAPHY). A FEW TORNADOES AND SOME HAIL WILL LIKELY OCCUR IN ASSOCIATION WITH THESE UPDRAFTS. HAIL SIZE WILL BE MOSTLY BELOW SEVERE LIMITS OR MARGINALLY SEVERE GIVEN LOW WB0 HEIGHTS. IF DEVELOPMENT OF WIND FIELD IS SLIGHTLY MORE AGGRESSIVE THAN CURRENTLY ANTICIPATED AN UPGRADE TO HIGH RISK IS NECESSARY.

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