Hurricane JEANNE

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TROPICAL STORM JEANNE DISCUSSION NUMBER  27
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT MON SEP 20 2004

JEANNE HAS NOT CHANGED SIGNIFICANTLY IN ORGANIZATION OVER THE PAST
SEVERAL HOURS.  PEAK FLIGHT-LEVEL WINDS FROM THE AIR FORCE
HURRICANE HUNTER AIRCRAFT ARE ABOUT THE SAME AS ON THE LAST RECON
MISSION...ALTHOUGH THE CENTRAL PRESSURE IS DOWN A COUPLE OF
MILLIBARS.  CURRENT INTENSITY IS HELD AT 50 KT.  THE HURRICANE
HUNTERS FIXED THE CENTER OF THE STORM NEAR THE SOUTHERN PORTION OF
THE CONVECTIVE OVERCAST...AND SATELLITE ANALYSTS FROM TAFB...SAB...
AND AFWA LOCATED THE CENTER SLIGHTLY FARTHER NORTH.  ON SATELLITE
IMAGES...THE CLOUD PATTERN IS BECOMING A LITTLE ELONGATED FROM
SOUTHWEST TO NORTHEAST.  THIS IS INDICATIVE OF SOME SOUTHWESTERLY
SHEAR OVER THE SYSTEM...AND ANALYSES FROM THE UNIVERSITY OF
WISCONSIN CIMSS INDICATE A LITTLE OVER 15 KT OF VERTICAL SHEAR IN
THE AREA.  SOME STRENGTHENING IS FORECAST AS PER THE PREVIOUS
ADVISORIES AND THE LATEST SHIPS GUIDANCE.  A FURTHER INCREASE IN
SHEAR AND DRIER AIR IS LIKELY TO HALT THE INTENSIFICATION PROCESS
IN A COUPLE OF DAYS.  HOWEVER...IF THE SHEAR INCREASES
SIGNIFICANTLY AND SOONER THAN EXPECTED...JEANNE MIGHT NOT REGAIN
HURRICANE STATUS AFTER ALL.

THE ESTIMATED INITIAL MOTION CONTINUES TO BE  A LITTLE EAST OF
NORTH...010/7.  THE STORM IS CURRENTLY BEING STEERED BY THE FLOW
BETWEEN A WEAK MID-LEVEL TROUGH TO ITS NORTHWEST AND A RIDGE TO ITS
EAST.  THERE IS A MUCH LARGER AND STRONGER TROUGH TO THE
NORTH-NORTHEAST OF JEANNE...AND THE GFS MODEL PREDICTS THAT THE
TROPICAL CYCLONE WILL BE ENTRAINED INTO THE FLOW ON THE SOUTH SIDE
OF THIS BIGGER TROUGH...AND MOVE WELL EAST INTO THE OPEN ATLANTIC
BY THE END OF THE FORECAST PERIOD.  THE GFDL...U.K. MET...AND
NOGAPS MODELS DO NOT AGREE WITH THAT SCENARIO...AND SHOW THE LARGE
TROUGH LEAVING JEANNE BEHIND.  THOSE MODELS DEPICT VARIOUS VERSIONS
OF A LOOP BACK TO THE WEST...WITH THE TROPICAL CYCLONE FEELING THE
INFLUENCE OF A STRONG MID-TROPOSPHERIC HIGH OVER THE EASTERN UNITED
STATES.  AS HAS BEEN THE CASE FOR SOME TIME NOW...THERE IS
CONSIDERABLE UNCERTAINTY IN THE FORECAST TRACK FOR JEANNE IN THE
2-5 DAY TIME FRAME.  THIS OFFICIAL TRACK FORECAST IS A COMPROMISE OF
THE VARIOUS MODEL SOLUTIONS...AND SIMPLY HOLDS THE SYSTEM STATIONARY
AFTER DAY 3. 

FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0900Z 26.0N  71.9W    50 KT
 12HR VT     20/1800Z 26.7N  71.4W    55 KT
 24HR VT     21/0600Z 27.3N  70.5W    60 KT
 36HR VT     21/1800Z 27.3N  69.5W    65 KT
 48HR VT     22/0600Z 27.0N  68.7W    70 KT
 72HR VT     23/0600Z 26.5N  68.0W    70 KT
 96HR VT     24/0600Z 26.5N  67.5W    65 KT
120HR VT     25/0600Z 26.5N  67.5W    60 KT
 
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