CONVECTIVE FORECAST
VALID 06Z SUN 15/06 - 06Z MON 16/06 2003
ISSUED: 14/06 19:32Z
FORECASTER: HUGO

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL FRANCE

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL, NORTHERN ITALY

GENERAL THUNDERSTORMS ARE FORECAST ACROSS SOUTHERN NORWAY & SWEDEN

GENERAL THUNDERSTORMS ARE FORECAST ACROSS BELARUS, NORTHERN UKRAINE & PARTS OF WESTERN RUSSIA

GENERAL THUNDERSTORMS ARE FORECAST ACROSS A LARGE SECTION OF CENTRAL & SOUTHERN EUROPE EXCLUDING THE SLGT RISK ZONES

SYNOPSIS

A RIDGE OF THE AZORES HIGH WILL BE EFFECTING THE MAJORITY OF THE UK THROUGHOUT THE FORECAST PERIOD IN ASSOCIATION WITH AN UPPER SHORT WAVE RIDGE AHEAD OF A CLOSED 500MB CYCLONIC PATTERN WITHIN THE CENTRAL NORTH ATLANTIC...HOWEVER A VERY WEAK SURFACE LOW PRESSURE WILL BE CROSSING THROUGH THE PATTERN TO THE NORTH OF SCOTLAND DURING THE FORECAST PERIOD IN ASSOCIATION WITH A WEAK PV FEATURE...A MINOR SHORT WAVE MID-LEVEL TROUGH IS DOMINATING PARTS OF NE=ERN EUROPE IN ASSOCIATION WITH A WEAK SURFACE LOW PRESSURE...THE REST OF CENTRAL & S=ERN EUROPE IS DOMINATED BY A SLACK SURFACE AND MID-LEVEL FLOW WITH SMALL MESOSCALE HIGH'S & LOW'S DOTTED THROUGHOUT THE REGION...A FRONTOLYSING COLD FRONT IS EFFECTING PARTS OF E=ERN EUROPE WITH A QUASI-STATIONARY AND WEAKENING COLD FRONT THROUGH FRANCE & INTO PARTS OF GERMANY

DISCUSSION

...CENTRAL FRANCE...
AS WITH RECENT DAYS CENTRAL FRANCE WILL BE AFFECTED BY A SLACK SURFACE PRESSURE REGION WITH A HIGH THERMAL GRADIENT TO THE SOUTH OF THE QUASI-STATIONARY COLD FRONT THROUGH N=ERN PARTS OF FRANCE...DIURNAL CONVECTIVE ACTIVITY IS EXPECTED ON A WIDESPREAD SCALE TO THE SOUTH OF THE COLD FRONT FEATURE...FORECAST SOUNDINGS THROUGH TOMORROW AFTERNOON & EVENING SHOW AN UNSTABLE ATMOSPHERE WITH FORECAST 30HPA MLCAPE VALUES BETWEEN 1200 & 1400J/KG WITH POSSIBLE SBCAPE VALUES EXCEEDING 2000J/KG...THE REGION IS VOID OF ANY SIGNIFICANT SHEAR BOTH LOW LEVEL AND DEEP LAYER SO THE RISK OF SUPERCELL DEVELOPMENT IS EXPECTED TO BE LOW OR NONE-EXISTENT ALSO IN RELATION TO LOW 0-3KM HELICITY...HOWEVER DUE TO THE LARGE EXPECTED CAPE VALUES AND REGIONAL CONVERGENCE ZONES THERE IS A MODERATE TO HIGH RISK OF MULTICELL DEVELOPMENT...MEDIUM SIZED HAIL IS EXPECTED (>1") IN ASSOCIATION WITH THE LARGE AMOUNT OF AVAILABLE CAPE AND ALSO HIGHLY FAVOURABE WBZ HEIGHTS OF BETWEEN 7500FT AND 8500FT...LARGE RAINFALL TOTALS ARE ALSO EXPECTED AND WITH LITTLE OR NO MID TO UPPER LEVEL STEERING FLOW THEN CONVECTIVE DEVELOPMENT IS EXPECTED TO BE SLOW MOVING POSSIBLY LEADING TO FLASH FLOODING IN PARTS...T2GUST FORECASTS ARE BETWEEN 30 & 40MPH SO SOME MODERATE LOCALISED WIND GUSTS ARE POSSIBLE...CONVECTION WILL REMAIN THROUGHOUT A LARGE PART OF THE EVENING BUT SHOULD SLOWLY DECAY AFTER SUNSET.

...CENTRAL, NORTHERN ITALY...
CENTRAL AND N=ERN REGIONS OF ITALY WILL BE EFFECTED BY DIURNAL CONVECTIVE DEVELOPMENT IN ASSOCIATION WITH TWO MESOSCALE LOW PRESSURE FEATURES TO THE WEST AND EAST OF THE COUNTRY...CONVECTION WILL INTITIATE DURING THE LATTER STAGES OF THE MORNING HOURS AND INTO THE AFTERNOON AS SOLAR INPUT INCREASES...FORECAST SOUNDINGS FOR THE REGION ARE VERY UNSTABLE WITH 30HPA MLCAPE VALUES IN EXCESS OF 2000J/KG ALONG WITH LIFTED INDICIES BETWEEN -5 AND -6...SBCAPE DOES EXCEED 3000J/KG HOWEVER THERE IS A MODERATE LEVEL OF CIN PRESENT (>-70J/KG) AT THAT STAGE...WITH FORECAST CAPS OF BETWEEN 2C AND 3C CONVECTION MAYBE PROHIBITED FOR A TIME AND A 'LOADED GUN' SITUATION MAYBE POSSIBLE INTO THE AFTERNOON ONCE HIGH TEMPERATURES AND A VERY HIGH LOWEST 30HPA WBPT TEMPERATURES OF >20C TAKE EFFECT ALLOWING THE RELEASE OF BUILT-UP DIURNAL HEAT...LOW LEVEL AND DEEP LAYER SHEAR IS WEAK (0-6KM <15KT), HOWEVER WITH A LIMITED S.C.P VALUE (<2)TO THE SOUTH OF ALPS THERE IS A LOW RISK OF ISOL SUPERCELL DEVELOPMENT...THERE IS HOWEVER A HIGH RISK OF MULTICELL ACTIVITY IN ASSOCIATION WITH THE LARGE CAPE VALUES AND POSSIBLE CONVERGENCE ZONES...THERE IS A RISK OF MEDIUM SIZED HAIL BUT WITH UNFAVOURABLE WBZ HEIGHTS (>10,000FT) LARGE HAIL IS GENERALLY NOT EXPECTED...WITH LITTLE OR NO MID TO UPPER LEVEL STEERING FLOWS FLASH FLOODING IS POSSIBLE AS ANY CONVECTIVE ACTIVITY WILL BECOME SLOW MOVING...T2GUST FORECASTS ARE BETWEEN 40 AND 50MPH SO SOME MODERATE TO STRONG WIND GUSTS ARE POSSIBLE...CONVECTION WILL REMAIN THROUGH A LARGE OF THE EVENING BUT WILL SLOWLY DECAY DURING THE NIGHT.

...SOUTHERN NORWAY & SWEDEN...
A WEAK SURFACE AREA OF LOW PRESSURE OVER S=ERN NORWAY & SWEDEN DOES BRING THE RISK OF SOME GENERAL TSTSM ACTIVITY DURING THE FORECAST PERIOD...HOWEVER ANY CONVECTIVE ACTIVITY IS EXPECTED TO BE KEPT TO A MINIMUM IN ASSOCIATION WITH A LACK OF SURFACE HEATING PARTIALLY CAUSED BY ASSOCIATED FRONTAL FEATURES AND CLOUD BUT ALSO RELATIVELY LOW ATMOSPHERIC THICKNESS VALUES & SURFACE TEMPERATURES...FORECAST SOUNDINGS SHOW SOME LIMITED SBCAPE (200J/KG) BUT NOTHING MORE. ANY ISOL TO SCT TSTSM ACTIVITY IN ASSOCIATION WITH THIS FEATURE WILL QUICKLY DISPERSE TOWARDS SUNSET.

...BELARUS, N=ERN URKAINE & PARTS OF W=ERN RUSSIA...
THESE REGIONS WILL BE AT RISK OF GENERAL TSTSM ACTIVITY IN ASSOCIATION WITH A WEAK SURFACE LOW PRESSURE AND A SHORT WAVE 500MB TROUGH WITH ITS ASSOCIATED PV REGION OVER THE AREA...FORECAST SOUNDINGS FOR THE REGION SHOW ONLY LIMITED MLCAPE VALUES (<300J/KG) HOWEVER THERE IS SOME REASONABLE DEEP LAYER SHEAR (0-6KM >30KT) IN CONJUNCTION WITH A 300MB JET INTERACTING WITH THIS FEATURE AND ALSO SOME LOW LEVEL SHEAR (0-1KM >15KT)...IF CONVECTION CAN BE INTIATED IN RELATION TO SOLAR INPUT DURING THE DAY AND ALSO DYNAMIC FORCING IN ASSOCIATION WITH THE FRONTAL FEATURES THERE IS A RISK OF SOME LIMITED ORGANISATION, ESPECIALLY ALONG THE COLD FRONT OTHERWISE NO MAJOR TSTSM ACTIVITY IS EXPECTED WITH THIS FEATURE AT PRESENT.

...REST OF CENTRAL, S=ERN EUROPE EXCLUDING SLGT RISK REGIONS...
THE REST OF CENTRAL, S=ERN EUROPE IS AT RISK OF DIURNAL CONVECTIVE ACTIVITY IN ASSOCIATION WITH THE SLACK SURFACE PRESSURE GRADIENTS AND ALSO REASONABLE LOW ATMOSPHERIC PRESSURE (<1013MB) AND ALSO SMALL MESOSCALE LOWS AND HEAT LOWS...WITH HIGH SURFACE TEMPERATURES EXPECTED IN ASSOCIATION WITH A HIGH 1000-500MB THICKNESS (>564DAM) CONVECTION WILL INITIATE DURING THE LATTER STAGES OF THE MORNING AND INTO THE AFTERNOON, ESPECIALLY ACROSS PARTS OF GREECE AND SPAIN...FORECAST SOUNDINGS SHOW MODERATELY UNSTABLE ATMOSPHERES WITH MLCAPE VALUES RANGING BETWEEN 800 AND 1500J/KG...CONVERGENCE ZONES WILL BE FOCAL POINTS FOR POSSIBLE MULTICELL DEVELOPMENT ESPECIALLY SEA BREEZE CONVERGENCE ZONES ACROSS THE SPANISH PLATEAU...WITH WEAK LOW LEVEL AND DEEP LAYER SHEAR ACROSS THE MAJORITY OF CENTRAL & S=ERN EUROPE THERE IS LITTLE OR NO RISK OF ANY SUPERCELL DEVELOPMENT BUT SOME MODERATE SIZED HAIL, MODERATE WIND GUSTS AND TORRENTIAL RAINFALL ARE POSSIBLE ESPECIALLY JUST BEFORE THE MATURING STAGE OF THE CONVECTIVE CYCLE IS REACHED...A SLGT RISK MAYBE NEEDED FOR SPECIFIC REGIONS DURING THE COURSE OF THE AFTERNOON DEPENDING ON THE OVERAL TSTSM ORGANISATION & ACTIVITY THAT OCCURS.

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