CONVECTIVE FORECAST
VALID 06Z THU 08/05 - 06Z FRI 09/05 2003
ISSUED: 07/05 19:17Z
FORECASTER: GATZEN

GENERAL THUNDERSTORMS ARE FORECAST ACROSS CENTRAL EUROPE

GENERAL THUNDERSTORMS ARE FORECAST ACROSS WESTERN EUROPE

GENERAL THUNDERSTORMS ARE FORECAST ACROSS SOUTHEASTERN EUROPE

GENERAL THUNDERSTORMS ARE FORECAST ACROSS WESTERN MEDITERRANEAN

SYNOPSIS

CUT-OFF LOW PLACED OVER IBERIAN PENINSULA ... AND UPPER RIDGE PRESENT OVER CENTRAL/EASTERN EUROPE. ALONG IT'S AXIS, WARM AND DRY AIRMASS SPREADS OVER SOUTHERN CENTRAL EUROPE. RAWINSONDE DATA INDICATE STEEP LAPSE RATES WITHIN THIS AIRMASS. AT LOWER LEVELS ... COLD AND DRY AIR HAS ENTERED INTO NORTHERN EUROPE. SOUTH OF NORTHERN FRANCE, CENTRAL GERMANY, CENTRAL POLAND AND WHITE RUSSIA ... RELATIVELY WARM AIRMASS PERSISTS WITHIN THE BOUNDARY LAYER.

DISCUSSION

...CENTRAL EUROPE...
UPPER JET STREAK ATTM OVER WESTERN MEDITERRANEAN HEADS NORTHWARD AS CORIOLIS FORCE DIVERTS IT TO THE EAST. THE JET STREAK IS EXPECTED OVER SOUTHEASTERN GERMANY ON FRIDAY, 00 UTC. UNDERNEATH ... STATIONARY WARMFRONT OVER BENELUX ... CENTRAL GERMANY ... CENTRAL POLAND IS FORECAST TO OCCLUDE AS COLDFRONT OVER SOUTHWESTERN EUROPE MOVES INTO SOUTHERN GERMANY. AHEAD OF THE COLDFRONT ... MODELS SUGGEST STRONG MOISTURE RETURN INTO CENTRAL GERMANY, ESPECIALLY ALONG THE WAMRFRONT'S CONVERGENCE ... WITH DEW POINTS UP TO 15C IN THE AFTERNOON (GFS). ABOVE THE BOUNDARY LAYER ... WARM AND DRY AIRMASS OVER SOUTHERN CENTRAL EUROPE SPREADS NORTHEASTWARD ... AND STEEP LAPSE RATES YIELD TO CAPE VALUES IN THE ORDER OF 1000 J/KG. WITHIN THE DAY ... CONVECTION SHOULD INITIATE AT THE TRIPLE POINT AND SPREAD EASTWARD ALONG THE FRONTAL BOUNDARY. UPPER JET STREAK SHOULD SUPPORT ORGANISED CONVECTION OVER GERMANY ... AND SUPERCELLS MAY FORM ALONG AND NORTH OF MENTIONED WARMFRONT, WHERE SHR SHOULD BE ENHANCED. LARGE HAIL, STRONG WIND GUSTS AND A FEW TORNADOS SHOULD BE POSSIBLE IF THIS SCENARIO COMES TRUE ... HOWEVER ... AFFECTED AIRMASS HAS NOT A HISTORY OF PRODUCING STRONG CONVECTION, AND SOUNDINGS DO NOT INDICATE DEEP MOISTURE ABOVE THE SURFACE. LATER OBSERVATIONS MUST BE AWAITED TO ISSUE A CATEGORICAL RISK. TO THE SOUTH ... SHOWERS AND THUNDERSTORMS SHOULD FORM AHEAD AND ALONG THE COLD FRONT. SYNOPTIC SCALE UVM SHOULD BE WEAK SE OF THE JETSTREAK, AND SOUNDINGS SHOW LARGE CIN OVER PARTS OF SOUTHERN CENTRAL EUROPE. HOWEVER ... CONVECTION SHOULD DEVELOP WITH OROGRAPHIC SUPPORT. OVER SOUTHEASTERN CENTRAL EUROPE ... MODELS SUGGEST CONVERGENCE LINE WITHIN THE WAA-REGIME. INSTABILITY SEEMS TO BE SOMEWHAT BETTER THAN OVER GERMANY, AND THUNDERSTORMS SHOULD DEVELOP IN THE AFTERNOON. SEVERE THUNDERSTORMS ARE NOT LIKELY AS VERTICAL WIND SHEAR REMAINS QUITE LOW WITHIN THE DAY. HOWEVER ... OROGRAPHY COULD INFLUENCE LOW LEVEL SHEAR SOMEHOW ... AND INTERACTION OF CELLS COULD LEAD TO ISOLATED ENHANCED SRH. AS A CONSEQUENCE, SUPERCELLS ARE NOT RULED OUT ATTM. ISOLATED LARGE HAIL AND STRONG WIND GUSTS WILL BE POSSIBLE THEN.

...WESTERN EUROPE...
RELATIVELY COLD AND HUMID AIRMASS AFFECTS WESTERN EUROPE. DIURNAL INSTABILITY SHOULD ALLOW CONVECTION TO DEVELOP UNDERNEATH THE TROUGH AXIS. STRONG THUNDERSTORMS ARE NOT EXPECTED DUE TO LOW SHEAR AND INSTABILITY.

...WESTERN MEDITERRANEAN...
EAST OF CUT-OFF LOW ... UVM IS FORECAST OVER WESTERN MEDITERRANEAN ALONG THE FRONTAL BOUNDARY. INSTABILITY IS LOW BY NOW. HOWEVER ... THUNDERSTORMS SHOULD DEVELOP OVER NORTHERN AFRICA AND SPREAD NORTHWARDS INTO SOUTHWESTERN MEDITERRANEAN WITHIN THURSDAY EVENING/ NIGHT. AS DEEP LAYER SHEAR IS QUITE BIG, SOME ORGANISED THUNDERSTORMS MAY FORM. HOWEVER ... CHANCE FOR SEVERE THUNDERSTORMS SEEMS TO BE LOW AS INSTABIITY REMAINS WEAK.

#