VALID 12Z FRI 25/10 - 06Z SAT 26/10 2002
ISSUED: 25/10 12:26Z
FORECASTER: GATZEN

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS NORTHWESTERN EUROPE

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

GENERAL THUNDERSTORMS ARE FORECAST ACROSS EXTREMELY NW EUROPE

SYNOPSIS

IMPRESSING MID-LEVEL JET IS POINTING FROM THE ATLANTIC TOWARDS EUROPE. AT 300 HPA ... BOLAM ASSUMES MORE THAN 70 M/S OVER PARTS OF WESTERN EUROPE THIS EVENING. THIS JETSTREAK IS PROGGED OVER CENTRAL EUROPE TOMORROW MORNING. AT LOWER LEVELS ... STRONG LOW AT 12Z JUST WEST OF SCOTLAND IS STILL DEEPENING WHILE PROPAGATING WESTWARD. IN THE MEDITERRANEAN ... AMPLIFYING RIDGE WILL AFFECT MOST OF THE FORECAST REGION.

DISCUSSION

...NORTHWESTERN EUROPE...
STRONG UPPER JET IS FORECASTED TO REACH THE FORECAST AREA IN THE AFTERNOON WHILE IMPRESSIVE DELTA FLOW IS SITUATING OVER CENTRAL EUROPE. TILL TOMORROW MORNING JET AXIS WILL SWAY SOUTHWARD IN CONJUNCTION WITH STRONG CYCLONAL VORTICITY ADVECTION IN THE RANGE OF UPPER SHORT-WAVE-TROUGH. AT THE SURFACE ... INTENSE LOW WILL MIGRATE TO SOUTHERN SCANDINAVIA. IT'S WINDSTORM-AREA WILL WILL CROSS COMPLETE NORTHWESTERN EUROPE, WHILE THE MAIN FOCUS SHOULD BE FOUND OVER THE SOUTHERN NORTH SEA IN THE MORNING. FOCUS OF THUNDERSTORM DEVELOPMENT SHOULD SITUATE INSIDE COLD MIXED AIRMASS (AROUND 200 J/KG CAPE) WITHIN EXTENDING TROUGH. TOGETHER WITH THE STRONG UPPER JET ... CONTAINED SHORT-WAVES COULD CREATE GREAT VORTICITY ADVECTION IN CONJUNCTION WITH UPWARD/DOWNWARD VERTICAL MOTION. IF THUNDERSTORMS WILL DEVELOP ... INTERACTION OF CONVECTION AND VERTICAL MOTION FIELDS COULD RESULT IN INTENSIVE VORT-MAX SPEEDING WITHIN THE UPPER STREAM. IN ADDITION ... CONVECTION WILL LIKELY ORGANISE CONCERNING TO STRONG VERTICAL SHEAR. HOWEVER ... DMO SUGGEST THUNDERSTORM DEVELOPMENT BEHIND THE COLD FRONT AS OF TODAY AFTERNOON. WITH THESE STORMS ... SEVERE WINDGUSTS UP TO 70 KNOTS ARE EXPECTED OVER A WIDESPREAD AREA. IF OROGRAPHY WILL AFFECT LOW LEVEL WIND FIELD ... HUGE AMOUNTS OF HELICITY ARE IMAGINABLE ... AND ROTATING UPDRAFTS SHOULD BE ABLE TO FORM. WITH THESE SUPERCELLS ... DIME TO QUARTER-SIZED HAIL AND TORNADOS WILL BE POSSIBLE.

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