

130 

WWUS20 KWNS 241832

SEL8

SPC WW 241832

FLZ000-CWZ000-250100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 18

NWS STORM PREDICTION CENTER NORMAN OK

135 PM EST WED FEB 24 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTH FLORIDA

       COASTAL WATERS



EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 135 PM UNTIL

800 PM EST.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 65

STATUTE MILES EAST AND WEST OF A LINE FROM 15 MILES WEST

NORTHWEST OF VERO BEACH FLORIDA TO 70 MILES SOUTHWEST OF MIAMI

FLORIDA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



DISCUSSION...THUNDERSTORMS WILL CONTINUE INCREASING IN COVERAGE AND

INTENSITY ACROSS SRN FL THIS AFTERNOON.  17Z SPECIAL SOUNDING FROM

MFL INDICATE MODEST INSTABILITY BUT STEEP LAPSE RATES AND STRONG

LOW/DEEP LAYER SHEAR.  THIS SUGGESTS ADDITIONAL POTENTIAL FOR LARGE

HAIL AND DAMAGING WINDS AS ACTIVITY EVOLVES AS SUPERCELLS AND

CLUSTERS OF STRONGER STORMS.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 350. MEAN STORM

MOTION VECTOR 26020.





...EVANS

