DAY 1 CONVECTIVE OUTLOOK
VALID 22Z MON 09/12 - 12Z TUE 10/12 2002
ISSUED: 09/12 21:27Z
FORECASTER: HAVEN

GENERAL THUNDERSTORMS ARE FORECAST ACROSS SOUTHERN IBERIAN PENINSULA

GENERAL THUNDERSTORMS ARE FORECAST ACROSS CENTRAL AND SOUTHERN ITALY AND SURROUNDING SEA AREAS

SYNOPSIS

STRONG BLOCKING UPPER FLOW PATTERN OVER EUROPE WITH UPPER HIGH STATIONARY BETWEEN ICELAND AND NORTH SEA, AND UPPER LOW NORTHWEST OF PORTUGAL MOVING SLOWLY NORTHEAST. JETSTREAM REMAINS OVER EXTREME SOUTHWESTERN EUROPE AND FURTHER SOUTH OVER AFRICAN CONTINENT. EMBEDDED SPEED MAXIMUM, WEST OF IBERIAN PENINSULA IS ROTATING AROUND THE UPPER LOW, EXPECTED OVER SOUTHERN SPAIN EARLY ON TUESDAY. AT LOWER LEVELS... MUCH OF CONTINENTAL EUROPE HAS BEEN INVADED BY COLD, DRY CONTINENTAL AIR FROM RUSSIA, THEREBY REDUCING THUNDERSTORM CHANCES TO NEAR ZERO. SURFACE LOW OVER PORTUGAL IS NOT CHANGING MUCH WITH EASTWARD MOVING COLDFRONT OVER SPANISH-PORTUGESE BORDER AT 18Z.

DISCUSSION

...SOUTHERN IBERIAN PENINSULA...
METEOSAT IR LOOP OF THE LAST FEW HOURS SHOWS POPPING UP OF CONVECTION OVER SOUTHERN SPAIN ALONG COLDFRONT. LATEST DATA BY LIGHTNING DETECTION SYSTEM ALSO SHOW ISOLATED LIGHTNING STRIKES ARE OCCURING. AS COLDFRONT PROGRESSES EAST AND LEFT-EXIT REGION OF SPEED MAX OVERLAPS COLDFRONT...UVM WILL BE ENHANCED WITH INCREASING THUNDERSTORM COVERAGE AND INTENSITY EXPECTED OVER SOUTHEASTERN SPAIN/SOUTHWESTERN MEDITERRANEAN, TUESDAY MORNING. 40+ KTS DEEP LAYER SHEAR WILL BE SUFFICIENT FOR ORGANIZED MULTICELLS. HOWEVER...PROGSOUNDINGS SHOW ONLY LOW INSTABILITY /CAPE BELOW 150 J KG-1/ NEAR AND EAST OF COLDFRONT. BEHIND COLDFRONT... COLD AIR ALOFT AND LOW INSTABILITY MAY RESULT IN BRIEF THUNDERSTORM ACTIVITY.

......
NEAR COLDFRONT OVER SOUTHEASTERN SPAIN /SOUTHWESTERN MEDITERRANEAN AND BEHIND COLDFRONT OVER PORTUGAL/SOUTH OF 40N/ A FEW BRIEF /NEAR SEVERE/ GUSTS MAY OCCUR, BUT ALL OVER THREAT SEEMS TOO LOW TO WARRANT A SLIGHT RISK.

...CENTRAL AND SOUTHERN ITALY AND SURROUNDING SEA AREAS...
FRONTAL REMNANTS AND MINOR SURFACE LOW OVER THYRENIAN SEA AND IONIAN SEA ARE MOVING SLOWLY NORTHEAST. WEAK UPPER THROUGH EMBEDDED IN WESTERLY UPPER FLOW AT 20Z OVER NORTHERN THYRENEAN SEA CAN BE CLEARLY SEEN IN WV-IMAGERY AND IS MOVING EAST. LOW INSTABILITY AND WEAK VERTICAL SHEAR WILL STRONGLY LIMIT CHANCES FOR SEVERE WEATHER. THUNDERSTORM ACTIVITY IS EXPECTED TO DECREASE AS WEAK RIDGE APPROACHES FROM WEST TUESDAY MORNING.

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