MESO: Mesoscale Discussion 2118

ACUS11 KWNS 190738
SWOMCD
SPC MCD 190737
FLZ000-190830-

MESOSCALE DISCUSSION 2118
NWS STORM PREDICTION CENTER NORMAN OK
0237 AM CDT TUE AUG 19 2008

AREAS AFFECTED...CENTRAL AND SRN FL

CONCERNING...TORNADO WATCH 840...

VALID 190737Z - 190830Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 840 CONTINUES.

LOW LEVEL SHEAR PARAMETERS REMAIN FAVORABLE FOR TORNADOES WITHIN THE
ERN HALF OF T.S. FAY WHICH CONTINUES TO APPROACH THE SW FL COAST
EARLY THIS TUESDAY MORNING.

STRONG LOW LEVEL SHEAR /SFC-1 KM 30-35 KT/ WITHIN ERN PERIPHERY OF
T.S. FAY ENCOMPASSES MOST OF THE SRN HALF OF THE FL PENINSULA...AS
THE CENTER OF FAY /APPROXIMATELY 35 S APF AT 07Z/ CONTINUES TO
APPROACH THE SW FL COAST. LOW LEVEL SHEAR WILL CONTINUE TO INCREASE
WITH NWD EXTENT INTO CENTRAL FL THIS MORNING ALONG AND E OF THE
TRACK OF FAY. THIS WAS EVIDENT IN THE 06Z TPA SPECIAL SOUNDING
WHICH INDICATED SFC-1 KM SHEAR OF 30 KT AS COMPARED TO A VALUE OF 17
KT AT 00Z. REGIONAL RADARS INDICATED A STRONG CONVECTIVE BAND
LOCATED 30-50 NM EAST OF THE SE FL COAST WITH THIS BAND THEN ARCING
NWWD ACROSS PALM BEACH COUNTY TO LAKE OKEECHOBEE. EFFECTIVE BULK
SHEAR OF 30-35 KT EXTENDING FROM SE FL TO OFFSHORE AND MODERATE
INSTABILITY SUGGEST EMBEDDED SUPERCELL STRUCTURES WILL CONTINUE TO
DEVELOP WITHIN THIS OFFSHORE BAND AND THEN TRACK NWWD TO INLAND
LOCATIONS. ALTHOUGH OTHER CONVECTIVE BANDS EXTENDING FROM THE UPPER
KEYS AND INLAND TO SRN FL HAVE TENDED TO BE WEAKER IN INTENSITY...
STRONG LOW LEVEL SHEAR WILL ALSO SUPPORT LOW LEVEL STORM ROTATION.

GIVEN THAT THE CENTER OF FAY CONTINUES TO MOVE AWAY FROM THE LOWER
FL KEYS RESULTING IN VEERED LOW LEVEL WINDS...THE TORNADO THREAT
WILL LIKELY DIMINISH FROM THE KEYS INTO SW FL THE REST OF THE
MORNING.

..PETERS.. 08/19/2008

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MFL...MLB...KEY...TBW...

24388112 25268114 25888160 26138190 26608237 26978231
28378211 28408102 28838075 28378027 27057964 25437966
24757983 24578039

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