DAY 1 CONVECTIVE OUTLOOK
VALID 06Z SUN 23/03 - 06Z MON 24/03 2003
ISSUED: 23/03 01:42Z
FORECASTER: VAN DER VELDE

GENERAL THUNDERSTORMS ARE FORECAST ACROSS WRN SPAIN, PORTUGAL

GENERAL THUNDERSTORMS ARE FORECAST ACROSS GREECE/AEGEAN SEA, SICILY

SYNOPSIS

HIGH PRESSURE AREA DOMINATING EUROPE FOR ALREADY MORE THAN A WEEK, SITUATED OVER ERN EUROPE ATTM, BUILDS IN SWRN DIRECTION TOWARDS S-CNTRL EUROPE. SHALLOW LOW WITH UNSTABLE AIR OVER THE IBERIAN PENINSULA MOVES NORTHWARD. AT THE EASTERN PERIPHERY OF THE HIGH, AN ULL WITH INTENSIFYING GRADIENT AT ITS WESTERN SIDE DESCENDS INTO THE ERN MEDITERRENEAN LATER IN THE FORECAST PERIOD, THE COLD UPPER AIR CAUSING DESTABILIZATION OF THE AIRMASS OVER SEA.

DISCUSSION

...WRN SPAIN, PORTUGAL...
GFS MODEL INDICATES INSTABILITY IN THE ORDER OF A FEW HUNDRED J/KG CAPE AND CONVERGENT SFC FLOW OVER THE WESTERN IBERIAN PENINSULA ...WITH LITTLE TO NO CAPPING INVERSION. PREVIOUS DAY TSTM ACTIVITY IN THIS REGION ALREADY SEEMED TO BE SURFACE-BASED UNDER INFLUENCE OF CONVERGENT SURFACE FLOW AND LOCAL OROGRAPHY INDUCED LIFT. THE 00Z GIBRALTAR SOUNDING SHOWS THAT THE CAP PRESENT IN THE 12Z SOUNDING HAS CONSIDERABLY WEAKENED. THIS MEANS THAT TSTMS SHOULD BE ABLE TO FORM AGAIN, PROBABLY ALREADY BY EARLY-MID AFTERNOON. SHEAR PROFILES INDICATED BY THE PRESENT SOUNDINGS ARE VERY WEAK. PORTUGAL SEEMS TO BE THE MOST FAVORED AREA FOR TSTM ACTIVITY TOMORROW, WITH THE HIGHEST THETA-E AND CONVERGENCE.

...GREECE/AEGEAN SEA, SICILY...
SICILY WILL LIKELY SEE SOME MINOR TSMS AT THE START OF THE FCST PERIOD AS THE COLD FRONT LEADING THE COLD CONTINENTAL AIRMASS PASSES, WITH SOME CVA AHEAD OF THE 500 HPA TROUGH AND SOME CAPE INDICATED BY THE GFS MODEL. DRY AIR ALOFT COULD CAUSE SOME INTENSE DOWNDRAFTS, BUT NOT ENOUGH TO WARRANT A RISK. BETWEEN 00Z AND 06Z ON MONDAY, THE ULL DESCENDING INTO THE ERN MEDITERRANEAN WILL CAUSE INSTABILITY OVER THE AEGEAN SEA. THE LEFT EXIT OF THE JETSTREAK AT THE WRN SIDE OF THIS AREA WILL BE SUFFICIENT TO TRIGGER WIDESPREAD TSMS DURING THE EARLY MONDAY MORNING. HOWEVER, GFS MODEL INDICATED VERTICAL SHEAR OVER THE AEGEAN SEA ITSELF WILL BE RATHER WEAK. THERE MAY BE A POSSIBILITY OF NON-SUPERCELL WATERSPOUTS IN THIS AREA HOWEVER, GIVEN THE STRONG INSTABILITY AND LOW VERTICAL SHEAR. GUSTS UP TO 40 KTS (BELOW SEVERE LIMITS) WILL BE POSSIBLE WITH THIS CONVECTION. ISOLATED TSMS ARE POSSIBLE IN THE REMAINDER OF THE GEN TSMS AREA IN THE MEDITERRENEAN.

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