DAY 1 CONVECTIVE OUTLOOK
VALID 16Z SAT 01/03 - 06Z SUN 02/03 2003
ISSUED: 01/03 15:45Z
FORECASTER: DAHL

GENERAL THUNDERSTORMS ARE FORECAST ACROSS THE BISKAY ... SOUTHERN FRANCE ... THE NORTHWESTERN MEDITERRANEAN SEA.

SYNOPSIS

SPLIT-FLOW PATTERN REMAINING IN PLACE OVER EUROPE ... WITH A NEGATIVELY TILTED QUASI-STATIONARY UPPER LONG-WAVE TROUGH STRETCHTING FROM JUST S OF GREENLAND INTO WESTERN EUROPE. SHORTWAVE TROUGH AT THE SOUTHERN PERIPHERY OF THE MAIN TROUGH IS EXPECTED TO SHIFT SOUTHEASTWARDS RAPIDLY ... BECOMING PART OF THE SOUTHERN FRONTAL ZONE OVER THE NORTH-CENTRAL MEDITERRANEAN SEA. EASTWARD MOVING UPPER CUT-OFF LOW ATTM OVER NE LYBIA IS GAINING INCREASING INFLUENCE ON THE SOUTH CENTRAL MEDITERRANEAN SEA DURING THIS PERIOD. COLD FRONT/OCCLUSION ASSOCIATED WITH THE MAIN UPPER TROUGH WILL MOVE INTO THE WESTERN MEDITERRANEAN SEA AHEAD OF THE SHORTWAVE TROUGH UNTIL SUNDAY 06Z.

DISCUSSION

...BISKAY ... SOUTHERN FRANCE ... NORTHWESTERN MEDITERRANEAN ...
LARGE BAND OF ENHANCED CU/CB HAS FORMED AHEAD OF VORT MAX ASSOCIATED WITH THE ATLANTIC SHORT-WAVE TROUGH. THIS FEATURE SHOULD MAKE LANDFALL SATURDAY EVENING AND CROSS SOUTHERN FRANCE DURING THE NIGHT. INSTABILITY WILL BE RATHER MEAGER AS LAPSE RATES SHOULD BE NEARLY NEUTRAL IN THE POSTFRONTAL ENVIRONMENT. HOWEVER ... SHEAR WILL BE SUBSTANTIAL ... WITH 0-6 KM MAGNITUDES EXPECTED IN THE 70 KNOTS RANGE. SHAPE OF THE HODOGRAPH IN THE LOWEST KILOMETERS IS HARD TO ANTICIPATE GIVEN THE COMPLEX TERRAIN WHICH IS LIKELY TO PERTURB THE LOW-LEVEL WIND FIELD LOCALLY SO AS TO YIELD LARGE SRH VALUES. THUS ... GIVEN VIGOROUS LARGE-SCALE UPWARD FORCING ... STRONG VERTICAL SHEAR AND SUSPECTED LOCAL HIGH SRH VALUES ... SOME POTENTIAL FOR ORGANIZED SEVERE TSTMS EXISTS. POTENTIAL PROBLEM WILL BE LEE EFFECTS OF THE PYRENEES THOUGH MODEL GUIDANCE SUGGESTS THAT LOW-LEVEL FLOW WILL ALLIGN PARALLEL TO THE MOUNTAIN RANGE WITH SUSTAINED MOISTURE INFLUX FROM THE WESTERN ATLANTIC OCEAN ... AND ALLOVER CONFIDENCE THAT CONVECTION WILL BE MAINTAINED OVER THE NIGHT IS RATHER HIGH ... WITH PRIMARY THREATS EXPECTED TO BE STRONG/DAMAGING WIND GUSTS ALONG WITH SMALL HAIL. HOWEVER ... GIVEN SLIGHT CHANCES OF ISOLATED SHALLOW SUPERCELLS WITH QUITE LOW LCL HEIGHTS ... A BRIEF TORNADO OR TWO MAY BE POSSIBLE. IN HIGHER ELEVATIONS OF S FRANCE ... HAIL EXCEEDING SEVERE LEVELS MAY OCCUR.

...SOUTHERN MEDITERRANEAN SEA ...
POSSIBLY EVELATED TSTMS JUST OFF THE LYBIAN NORTH COAST APPEAR TO BE ASSOCIATED WITH A WEAK VORT MAX ROTATING ABOUT THE UPPER-LOW CENTER AS WELL AS SUBTLE LOW-LEVEL THETA-E ADVECTION. GIVEN SUSTAINED MOISTURE INFLUX FROM THE SOUTHERN MEDITERRANEAN SEA ... TSTMS MAY CONTINUE OVER THE VERY SOUTHERN MEDITERRANEAN SEA DURING THE NIGHT ... HOWEVER ... PRESENT THINKING IS THAT ACTIVITY WILL REMAIN OUTSIDE THE FORECAST AREA.

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