[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 240843
TCDAT1
HURRICANE JEANNE DISCUSSION NUMBER  43
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT FRI SEP 24 2004

THE INTENSITY OF JEANNE IS A BIT OF A PUZZLE THIS MORNING.  AN AIR
FORCE RESERVE HURRICANE HUNTER AIRCRAFT MEASURED A CENTRAL PRESSURE
OF 969 MB...WHICH WOULD NORMALLY SUPPORT WINDS OF NEAR 90 KT.
HOWEVER...THE MAXIMUM FLIGHT-LEVEL WINDS REPORTED BY THE AIRCRAFT
AT 700 MB WERE ONLY 74 KT...WHICH WOULD SUPPORT CLOSER TO 65 KT
SURFACE WINDS.  POST-ECLIPSE SATELLITE IMAGES SHOW SOME COOLING OF
THE CLOUD TOPS OVER THE SOUTH QUADRANT...BUT ALSO SHOW A MUCH LESS
DEFINED EYE.  BASED MAINLY ON THE CENTRAL PRESSURE...THE INITIAL
INTENSITY IS SET TO 85 KT.  HOWEVER...THIS MAY BE GENEROUS.

THE INITIAL MOTION IS NOW 270/7.  WATER VAPOR IMAGERY SHOWS THAT A
DEEP-LAYER ANTICYCLONE OVER THE EASTERN UNITED STATES IS NOW
CENTERED NEAR THE DELMARVA PENINSULA.  LARGE-SCALE MODELS INDICATE
THIS SYSTEM WILL CONTINUE TO SHIFT TO THE SOUTHEAST AND ELONGATE
SOUTHWARD WITH TIME.  THIS PATTERN EVOLUTION SHOULD KEEP JEANNE ON
A GENERAL WESTWARD COURSE FOR 36-48 HR...FOLLOWED BY A TURN TOWARD
THE NORTHWEST AND EVENTUAL RECURVATURE INTO THE WESTERLIES.  THE
TIMING OF THE TURN IS STILL IN QUESTION...AS THE GFDL HAS SHIFTED
FAR ENOUGH TO THE EAST TO MISS THE FLORIDA COAST...WHILE THE NOGAPS
DRIVES JEANNE ACROSS SOUTHERN FLORIDA TO THE GULF OF MEXICO BEFORE
RECURVATURE.  THE OTHER DYNAMICAL MODELS ARE BETWEEN THESE TWO
EXTREMES.  THE OFFICIAL FORECAST TRACK KEEPS JEANNE ON THE LEFT SIDE
OF THE GUIDANCE DURING THE FIRST 36-48 HR...AS THE RIDGE TO THE
NORTH MAY NOT ALLOW AS MUCH NORTHWARD MOTION AS SHOWN BY THE GFDL
AND GFS.  AFTER THAT...THE TRACK FOLLOWS THE MODEL CONSENSUS.
IT SHOULD BE NOTED THAT THE UKMET AGAIN APPEARS TO BE TOO FAST IN
THE FIRST 12 HR.

THE AIRCRAFT DATA INDICATES THAT JEANNE CURRENTLY HAS A BROAD WIND
FIELD...WITH A RADIUS OF MAXIMUM WINDS OF 35-45 NM.  BETWEEN THAT
AND THE COLD UPWELLING WATER THE HURRICANE IS CURRENTLY OVER...
LITTLE CHANGE IN STRENGTH IS LIKELY FOR 12 HR OR SO.  BEYOND THAT
TIME...JEANNE SHOULD MOVE OVER 82F WATER AND REACH 83-84F WATER BY
36 HR.  THIS COULD ALLOW FOR MORE SIGNIFICANT STRENGTHENING IF THE
STORM STRUCTURE HAS REORGANIZED BY THAT TIME...AND THE INTENSITY
FORECAST CALLS FOR JEANNE TO REACH 100 KT INTENSITY IN 48 HR.  THIS
IS SLIGHTLY HIGHER THAN BOTH SHIPS AND THE GFDL.  AFTER 48 HR...A
COMBINATION OF INCREASING SOUTHWESTERLY VERTICAL SHEAR AND LAND
INTERACTION SHOULD PRODUCE STEADY WEAKENING.

THE FORECAST TRACK AND WIND RADII REQUIRE A HURRICANE WARNING FOR
THE NORTHWESTERN BAHAMAS...A TROPICAL STORM WARNING FOR THE CENTRAL
BAHAMAS...AND A HURRICANE WATCH FOR PORTIONS OF THE FLORIDA EAST
COAST AT THIS TIME.

FORECASTER BEVEN

FORECAST POSITIONS AND MAX WINDS

INITIAL      24/0900Z 26.1N  71.6W    85 KT
 12HR VT     24/1800Z 26.1N  73.1W    85 KT
 24HR VT     25/0600Z 26.2N  75.4W    90 KT
 36HR VT     25/1800Z 26.6N  77.6W    95 KT
 48HR VT     26/0600Z 27.1N  79.5W   100 KT
 72HR VT     27/0600Z 30.0N  81.5W    80 KT...INLAND
 96HR VT     28/0600Z 34.0N  78.5W    50 KT...INLAND
120HR VT     29/0600Z 39.5N  69.5W    35 KT...OVER WATER


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