[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT41 KNHC 010832
TCDAT1
HURRICANE FRANCES DISCUSSION NUMBER  30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT WED SEP 01 2004

REPORTS FROM THE LATEST AIR FORCE RESERVE HURRICANE HUNTER
MONITORING FRANCES SHOW MAXIMUM FLIGHT-LEVEL WINDS AT 700 MB OF 123
KT...DOWN A LITTLE FROM THE EARLIER FLIGHT.  HOWEVER...THE CENTRAL
PRESSURE HAS DROPPED TO 935 MB.  BASED ON THIS...THE INITIAL
INTENSITY WILL REMAIN 120 KT FOR THIS ADVISORY.  THE WSR-88D AT SAN
JUAN SHOWS THAT FRANCES HAS CONCENTRIC EYEWALLS...AND THE AIRCRAFT
DATA SHOWS THREE CONCENTRIC WIND MAXIMA.  INDEED...ON THE LATEST
PASS THROUGH THE SOUTHEASTERN QUADRANT THE HIGHEST WIND WAS IN THE
MAXIMA ASSOCIATED WITH THE OUTER EYEWALL.

THE INITIAL MOTION IS A WOBBLY 285/15.  FRANCES REMAINS ON THE SOUTH
SIDE OF A SUBTROPICAL RIDGE WHICH LARGE-SCALE MODELS FORECAST TO
WEAKEN SOMEWHAT OVER THE NEXT 72 HR.  THIS SHOULD ALLOW THE
HURRICANE TO MOVE WEST-NORTHWESTWARD IN THE GENERAL DIRECTION OF
THE FLORIDA PENINSULA.  DYNAMICAL MODEL GUIDANCE AGREES WITH THIS
SCENARIO...EXCEPT FOR THE GFDL WHICH CONTINUES TO CALL FOR A
UNREALISTIC LOOKING MOTION TOWARD THE NORTHWEST.  THE OFFICIAL
FORECAST THROUGH 72 HR IS SHIFTED A LITTLE WEST OF THE PREVIOUS
TRACK BASED MAINLY ON THE INITIAL POSITION AND MOTION AND IS ON THE
LEFT SIDE OF THE DYNAMICAL GUIDANCE.  AFTER 72 HR...THERE IS
DIVERGENCE IN THE GUIDANCE AS A SHORTWAVE RIDGE DEVELOPS NORTH OF
FRANCES OVER THE EASTERN UNITED STATES.  THE OFFICIAL FORECAST
TRACK FOR THAT TIME IS SHIFTED TO THE SOUTHWEST OF THE PREVIOUS
TRACK...ALTHOUGH NOT AS FAR AS THE UKMET WHICH MARCHES FRANCES
WESTWARD ACROSS CENTRAL FLORIDA AND INTO THE GULF OF MEXICO.

THE INTENSITY FORECAST IS MODIFIED ONLY SLIGHTLY FROM THE PREVIOUS
PACKAGE.  UPPER-LEVEL WINDS ARE FAVORABLE THROUGH AT LEAST 36-48
HR...SO FRANCES SHOULD REMAIN STRONG.  A SLIGHT WEAKENING IS
INDICATED AT 72 HR BASED ON LAND INTERACTION AND SOME POSSIBLE
WESTERLY SHEAR.  THE MAIN CONTROLLING FACTOR ON INTENSITY WILL BE
THE STRUCTURE OF FRANCES AND CONCENTRIC EYEWALL CYCLES...BOTH OF
WHICH ARE DIFFICULT AT BEST TO TIME.  GIVEN THE CURRENT STRUCTURE
OF THE HURRICANE...CHANGES IN INTENSITY WILL LIKELY BE RELATIVELY
SLOW TO OCCUR.

FORECASTER BEVEN

FORECAST POSITIONS AND MAX WINDS

INITIAL      01/0900Z 21.2N  68.5W   120 KT
 12HR VT     01/1800Z 22.0N  70.6W   125 KT
 24HR VT     02/0600Z 23.2N  72.9W   125 KT
 36HR VT     02/1800Z 24.3N  74.8W   130 KT
 48HR VT     03/0600Z 25.5N  76.6W   130 KT
 72HR VT     04/0600Z 27.0N  79.5W   125 KT
 96HR VT     05/0600Z 28.5N  81.5W    85 KT...INLAND
120HR VT     06/0600Z 31.0N  84.0W    35 KT...INLAND


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