Hurricane IKE

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HURRICANE IKE DISCUSSION NUMBER  39
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092008
500 PM EDT WED SEP 10 2008
 
 
THE RECONNAISSANCE AIRCRAFT DATA SHOW THAT IKE HAS TWO WELL-DEFINED
WIND MAXIMA OF ROUGHLY EQUAL STRENGTH.  THE PEAK FLIGHT-LEVEL WINDS
OF 93 KT WERE FOUND IN A BAND ABOUT 90 NM EAST OF THE CENTER.  A
DROPSONDE WITHIN A FEW MILES OF THE CENTER REPORTED LOW-LAYER MEAN
WINDS OF 97 KT...WHICH CORRESPOND TO 82 KT AT THE SURFACE.  THE
ADVISORY WINDS ARE SET TO 85 KT ON THIS BASIS.  THE LARGE EXPANSE
OF HURRICANE AND TROPICAL STORM FORCE WINDS EXPLAINS THE APPARENT
MISMATCH BETWEEN THE PEAK WINDS AND THE CENTRAL PRESSURE.
CONDITIONS IN THE GULF OF MEXICO REMAIN FAVORABLE FOR
STRENGTHENING...INCLUDING LIGHT SHEAR AND STRONGLY DIFLUENT
UPPER-LEVEL OUTFLOW FOR THE NEXT DAY OR TWO.  ON THE OTHER
HAND...RECENT NORTHWARD SHIFTS IN THE TRACK NOW SUGGEST THAT IKE
MAY ENCOUNTER A COOL EDDY IN THE CENTRAL GULF AND MISS A WARM EDDY.
NEVERTHELESS...ALL OBJECTIVE GUIDANCE NOW MAKES IKE A MAJOR
HURRICANE AND THE OFFICIAL FORECAST IS INCREASED SLIGHTLY OVER THE
PREVIOUS FORECAST.  OTHER THAN INTERNAL EYEWALL DYNAMICS...WHICH
ARE IMPOSSIBLE TO FORECAST MORE THAN A FEW HOURS IN ADVANCE...I SEE
NO REASON WHY IKE SHOULD WEAKEN APPRECIABLY AS IT MOVES INTO THE
WESTERN GULF.
 
THE INITIAL MOTION IS 310/7.  THE TRACK FORECAST PHILOSOPHY IS
BASICALLY UNCHANGED.  IKE IS MOVING NORTHWEST TOWARD A WEAKNESS IN
THE SUBTROPICAL RIDGE.  THIS RIDGE IS FORECAST TO BUILD IN OVER THE
NEXT DAY OR TWO...WHICH SHOULD TURN THE TRACK BACK TO THE
WEST-NORTHWEST UNTIL IKE APPROACHES A DEEP LAYER TROUGH FORECAST TO
COVER THE WESTERN UNITED STATES IN TWO DAYS.  ALL GUIDANCE TURNS
IKE NORTHWARD TO VARYING DEGREES WITHIN A DAY OR SO OF PROJECTED
LANDFALL.  THERE HAS BEEN A NORTHWARD SHIFT IN SOME OF THE
GUIDANCE...MOST NOTABLY THE GFDL AND GFS.  IT IS TO BE EXPECTED
THAT SUBTLE CHANGES IN THE MODEL EVOLUTION OF THE WESTERN TROUGH
AND RIDGE OVER THE SOUTHEASTERN U.S. WILL LEAD TO GUIDANCE FLIP
FLOPS OVER THE NEXT COUPLE OF DAYS.  WITH THAT IN MIND...THE
OFFICIAL FORECAST IS NUDGED ONLY SLIGHTLY NORTHWARD.  IKE IS A VERY
LARGE HURRICANE...AND IS EXPECTED TO REMAIN LARGE AS
IT CROSSES THE GULF OF MEXICO.  REGARDLESS OF WHERE THE CENTER
CROSSES THE COAST...THE EFFECTS OF IKE WILL BE FELT OVER A LARGE
AREA.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/2100Z 24.5N  86.1W    85 KT
 12HR VT     11/0600Z 25.0N  87.4W    95 KT
 24HR VT     11/1800Z 25.6N  89.3W   105 KT
 36HR VT     12/0600Z 26.2N  91.5W   110 KT
 48HR VT     12/1800Z 27.0N  94.0W   115 KT
 72HR VT     13/1800Z 29.5N  97.0W    90 KT...INLAND
 96HR VT     14/1800Z 34.5N  95.5W    30 KT...INLAND
120HR VT     15/1800Z...ABSORBED IN FRONTAL ZONE
 
$$
FORECASTER FRANKLIN
 
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