[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 250858
TCDAT1
HURRICANE JEANNE DISCUSSION NUMBER  47
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT SAT SEP 25 2004

SATELLITE IMAGERY AND REPORTS FROM AN AIR FORCE RESERVE HURRICANE
HUNTER AIRCRAFT INDICATE THAT JEANNE CONTINUES TO MAINTAIN A 40 NM
WIDE EYE.  THE CENTRAL PRESSURE HAS DROPPED TO 958 MB...AND THE
AIRCRAFT REPORTED 700 MB FLIGHT-LEVEL WINDS OF ABOUT 100 KT.  THIS
IS THE BASIS FOR THE INITIAL 90 KT INTENSITY.  JEANNE IS CURRENTLY
GENERATING VERY COLD CLOUD TOPS SOUTH OF THE EYE...BUT A DRY SLOT
IS APPARENT NORTH OF THE EYE.  CIRRUS OUTFLOW IS CURRENTLY FAIR TO
GOOD IN ALL DIRECTIONS.  THE AIRCRAFT REPORTED 110 KT FLIGHT-LEVEL
WINDS AT 850 MB IN THE SOUTHWESTERN QUADRANT...APPARENTLY DUE TO AN
EYEWALL MESOVORTEX AND THE ASSOCIATED INTENSE CONVECTION.

THE INITIAL MOTION WOBBLES BETWEEN 270/12 AND 275/12.  JEANNE
REMAINS ON THE SOUTH SIDE OF A STRONG DEEP-LAYER RIDGE...WHICH
LARGE-SCALE MODELS NOW FORECAST TO PERSIST LONG ENOUGH TO DRIVE
JEANNE INTO SOUTHEASTERN OR EAST-CENTRAL FLORIDA IN ABOUT 24 HR.
BEYOND THAT TIME...THE RIDGE SHOULD WEAKEN AND MOVE FAR ENOUGH TO
THE EAST TO ALLOW JEANNE TO TURN NORTHWESTWARD...FOLLOWED BY
EVENTUAL RECURVATURE INTO THE WESTERLIES.  ALL GUIDANCE AGREES ON
THIS SCENARIO AND HAS SHOWN A WESTWARD SHIFT SINCE THE PREVIOUS
PACKAGE...BUT THERE REMAIN DIFFERENCES ON WHEN AND WHERE JEANNE
WILL TURN.  THE OFFICIAL FORECAST CONTINUES THE CURRENT MOTION
UNTIL LANDFALL IN FLORIDA IN 24 HR...THEN TURNS THE CYCLONE
NORTHWESTWARD AND NORTHWARD UP THE FLORIDA PENINSULA AND
NORTHEASTWARD ACROSS THE SOUTHEASTERN UNITED STATES.  THE FORECAST
TRACK IS ALONG THE SOUTHERN EDGE OF THE GUIDANCE FOR THE FIRST 24
HR...AND JUST EAST OF THE MODEL CONSENSUS FROM 24-72 HR.  IT HAS
BEEN SHIFTED WESTWARD FROM THE PREVIOUS PACKAGE...MOST NOTABLY OVER
THE FLORIDA PENINSULA.

GUIDANCE NOW SUGGESTS THAT UPPER-LEVEL WINDS WILL REMAIN FAVORABLE
FOR JEANNE TO STRENGTHEN UNTIL LANDFALL.  THEREFORE...THE MAIN
RESTRAINING FACTORS FOR DEVELOPMENT ARE THE CURRENT LARGE EYE...AND
THE ABUNDANT DRY AIR SURROUNDING THE HURRICANE.  SHIPS AND THE GFDL
BOTH TAKE JEANNE TO 100 KT BY LANDFALL.  GIVEN THE CURRENT
TRENDS...THE INTENSITY FORECAST WILL GO A LITTLE HIGHER AND CALL
FOR 105 KT.  IT WOULD NOT BE A SURPRISE TO SEE JEANNE GET STRONGER
THAN THAT...AND REACHING CATEGORY FOUR STATUS IS NOT OUT OF THE
QUESTION.  JEANNE SHOULD STEADILY WEAKEN AFTER LANDFALL...BECOMING
A DEPRESSION OVER THE SOUTHEASTERN UNITED STATES AND EVENTUALLY
BECOMING EXTRATROPICAL OVER THE NORTHWESTERN ATLANTIC.

FORECASTER BEVEN

FORECAST POSITIONS AND MAX WINDS

INITIAL      25/0900Z 26.5N  76.2W    90 KT
 12HR VT     25/1800Z 26.7N  78.2W   100 KT
 24HR VT     26/0600Z 27.3N  80.3W   105 KT...INLAND
 36HR VT     26/1800Z 28.6N  81.9W    75 KT...INLAND
 48HR VT     27/0600Z 30.4N  82.5W    45 KT...INLAND
 72HR VT     28/0600Z 34.0N  80.5W    30 KT...INLAND
 96HR VT     29/0600Z 38.5N  72.5W    30 KT...OVER WATER
120HR VT     30/0600Z 43.0N  62.0W    30 KT...EXTRATROPICAL


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