VALID 00Z TUE 15/10 - 00Z WED 16/10 2002
ISSUED: 14/10 22:32Z
FORECASTER: GROENEMEIJER

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS EXTREME SOUTHWESTERN BRITAIN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN IRELAND, SOUTHWESTERN BRITAIN AND EXTREME WESTERN FRANCE

GENERAL THUNDERSTORMS ARE FORECAST ACROSS TURKEY AND PARTS OF THE EASTERN MEDITERRANEAN

SYNOPSIS

STRONG WSW JET IS PRESENT OVER EASTERN ATLANTIC, INDUCING SURFACE CYCLOGENESIS 200 NW OF SPAIN. MOIST AIR IS TRANSPORTED NORTHWARD IN WARM SECTOR OF DEVELOPING SYSTEM WHERE FORCED ASCENT INIATIATES CONVECTION. A MARGINALLY UNSTABLY AIR-MASS IS IN PLACE OVER THE EXTREME SOUTHE EASTERN PART OF THE FORECAST AREA. ELSEWHERE STABILITY OF AIR-MASS PRECLUDES DEEP CONVECTIVE DEVELOPMENT.

DISCUSSION

...SOUTHERN IRELAND...SOUTHWESTERN BRITAIN...EXTREME WESTERN FRANCE...
RAPIDLY DEVELOPING LOW NOW LOCATED AT ABOUT 47.0N 11.5W WILL LIKELY TRACK NORTHEASTWARD. MOST MODELS SEEM TO UNDERESTIMATE ACTIVITY THOUGH HIRLAM AND MM5 SEEM TO BE CLOSE TO REAL INTENSITY. USING THESE MODELS AS A GUIDANCE, WE SHOULD FIRST NOTE THAT THE +06H OF HIRLAM RUN PUTS THE LOW SOMEWHAT TO FAR TO THE NORTHWEST AS VERFIED PER NOAA QUIKSCAT DATA. IT MIGHT HAVE PREDICTED THE LOW TO MATURE SOMEWHAT TOO FAST AND UNDERESTIMATED THE DEEPENING OF THE SYSTEM. MOREOVER, THE COURSE WILL LIKELY BE A BIT MORE EASTERLY. QUIKSCAT DATA SHOWS SUSTAINED 50 KT WINDS TO THE NORTH AND NORTHEAST OF THE LOW. ANOTHER /45KT/ WIND MAXIMUM IS OBSERVED TO THE SOUTH OF THE SYSTEM. MM5 AND HIRLAM LET THE LOW DEEPEN TO 983 HPA AT 12Z WITH CENTER LOCATED 150 KM WEST OF LANDS END, WHEREAS HIRLAM HAS THE LOW 300 KM WEST OF LANDS END WITH A CENTRAL PRESSURE OF 979 HPA. MM5 LETS THE LOW DEEPEN TO 981 AT 18Z LOCATED OVER SOUTHWESTERN WALES. KEEPING IN MIND THAT MM5 HAS A COURSER GRID THAN HIRLAM AND MIGHT NOT ME CAPABLE TO FULLY HANDLE THE SMALL SCALE OF THE SYSTEM WE EXPECT THE FOLLOWING COURSE:

12Z 150 KM WEST OF LANDS END, 979 HPA
18Z 50 KM WEST OF SOUTHWESTERN TIP OF WALES, 979 HPA
MM5 HAS AT 00Z 50 KT 925 HPA WINDS ASSOCIATED WITH THE SYSTEM, WHEREAS IT PREDICTS 60 KTS AT 12Z. A SIMILAR INCREASE IN SEA-SURFACE WINDS GIVES US 55-60 KT WINDS OR 10-11 BFT. OVER SOUTHEASTERN ENGLAND GUSTS OF NEAR 70 KNOTS CAN BE EXPECTED. IN IRELAND WINDS WILL LIKELY BE SOMEWHAT WEAKER, GUSTS OF UP TO 55 KNOTS ARE EXPECTED THERE.

...TURKEY...EASTERN MEDITERRANEAN...
ATMOSPHERE ACROSS THE AREA IS MARGINALLY UNSTABLE. RATHER WEAK SHEAR PROFILES PRECLUDE DEVELOPMENT OF SEVERE STORMS.

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