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Hurricane JEANNE


ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
HURRICANE JEANNE DISCUSSION NUMBER  35
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT WED SEP 22 2004
 
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT REPORTED A CENTRAL
PRESSURE OF 968 MB AT 0609Z WITH MAXIMUM FLIGHT-LEVEL WINDS OF 83
KT AT 700 MB IN THE SOUTHWESTERN EYEWALL.  A DROPSONDE IN THE
NORTHWESTERN EYEWALL SUGGESTED SURFACE WINDS OF ABOUT 80 KT. 
SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB REMAIN 77 KT...AND
THE MAXIMUM INTENSITY WILL REMAIN 80 KT.  ANALYSES FROM CIMMS AT
THE UNIVERSITY OF WISCONSIN INDICATE 15-20 KT OF WEST-SOUTHWESTERLY
VERTICAL SHEAR...AND WATER VAPOR IMAGERY SHOWS A LOT OF DRY AIR
SURROUNDING JEANNE.  SOME DRY AIR MAY HAVE REACHED THE SOUTHWESTERN
EYEWALL BASED ON THE AIRCRAFT DATA. 

THE INITIAL MOTION IS 180/3.  WATER VAPOR IMAGERY SHOWS A DEEP LAYER
TROUGH NORTHEAST OF JEANNE AND A LARGE-DEEP LAYER RIDGE CENTERED
OVER THE CENTRAL GREAT LAKES...WITH STRONG NORTHERLY FLOW BETWEEN
THE TWO FEATURES TO THE NORTH OF JEANNE.  LARGE-SCALE MODELS
FORECAST THE RIDGE BUILD OR MOVE EASTWARD INTO THE ATLANTIC DURING
THE NEXT 3-4 DAYS...WITH HEIGHTS FALLING OVER THE EASTERN UNITED
STATES BY DAYS 4-5.  THIS EVOLUTION SHOULD START JEANNE ON A
GENERAL WESTERLY TRACK IN 24 HR OR SO...THEN CAUSE A MORE NORTHWARD
MOTION AFTER 72-96 HR.  TRACK FORECAST GUIDANCE HAS COME INTO MUCH
BETTER AGREEMENT...WITH ALL THE DYNAMICAL MODELS...INCLUDING THE
GFS...AGREEING WITH THIS SCENARIO.  THE OFFICIAL FORECAST TRACK IS
SHIFTED SOUTHWARD DURING THE FIRST 36 HR...THEN IS SHIFTED
CONSIDERABLY TO THE WEST FROM THE PREVIOUS PACKAGE DURING THE REST
OF THE FORECAST PERIOD.  THE NEW TRACK IS JUST TO THE RIGHT OF THE
MODEL CONSENSUS.  IT IS POSSIBLE THE FORECAST TRACK MAY HAVE TO BE
SHIFTED FARTHER WEST ON SUBSEQUENT ADVISORIES.

WHILE THE TRACK FORECAST IS MORE CLEAR-CUT...THE INTENSITY FORECAST
REMAINS PROBLEMATIC.  LARGE-SCALE MODELS SUGGEST THE CURRENT SHEAR
MAY SUBSIDE AS A CUT-OFF LOW OR SHARP CYCLONIC SHEAR AXIS FORMS
NEAR FLORIDA IN ABOUT 24 HR.  INDEED...THE UPPER-LEVEL WINDS MAY
BECOME SOUTHEASTERLY OVER JEANNE.  HOWEVER...IT IS NOT TOTALLY
CLEAR WHETHER THIS SYSTEM WILL ACT AS AN OUTFLOW CHANNEL OR JUST
CHANGE THE DIRECTION OF THE SHEAR.  BY 48 HR... AN UPPER-LEVEL
ANTICYCLONE SHOULD DEVELOP OVER JEANNE PROVIDING A MORE FAVORABLE
ENVIRONMENT.  HOWEVER...NONE OF THE INTENSITY FORECAST MODELS...
EVEN EXPERIMENTAL ONES...FORECAST AN INTENSITY ABOVE 95 KT.  THE
REASONS FOR THIS ARE UNCLEAR...BUT IT COULD BE THAT THE DRY AIR IS
RESTRAINING THE DEVELOPMENT.  THE INTENSITY FORECAST WILL CALL FOR
MODEST STRENGTHENING...BUT IT WOULD NOT BE A SURPRISE TO SEE JEANNE
GET STRONGER THAN CURRENTLY FORECAST IN 72-96 HR.  THE MODELS HAVE
BACKED OFF A BIT ON THE SHEAR IN THE 96-120 HR TIMEFRAME...SO THE
FORECAST WILL SHOW LESS WEAKENING AT THAT TIME.

THE NEW FORECAST TRACK INCREASES THE THREAT TO THE SOUTHEASTERN
COAST OF THE UNITED STATES.  HOWEVER...IT IS TOO EARLY TO TELL
WHICH PART OF THE COAST...IF ANY...MAY BE AFFECTED BY JEANNE.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      22/0900Z 26.6N  68.6W    80 KT
 12HR VT     22/1800Z 26.3N  68.8W    80 KT
 24HR VT     23/0600Z 26.1N  69.5W    85 KT
 36HR VT     23/1800Z 26.1N  70.5W    85 KT
 48HR VT     24/0600Z 26.3N  71.8W    85 KT
 72HR VT     25/0600Z 27.0N  74.5W    85 KT
 96HR VT     26/0600Z 29.0N  77.0W    75 KT
120HR VT     27/0600Z 32.0N  78.0W    65 KT
 
 
$$
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Page last modified: Wednesday, 22-Sep-2004 08:33:27 UTC