Hurricane IKE

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HURRICANE IKE DISCUSSION NUMBER  42
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092008
1100 AM EDT THU SEP 11 2008
 
DATA FROM AIR FORCE AND NOAA AIRCRAFT INDICATE THAT IKE IS
MAINTAINING AN ATYPICAL WIND STRUCTURE...CHARACTERIZED BY A VERY
BROAD WIND FIELD WITH MULTIPLE WIND MAXIMA AND RELATIVELY LITTLE
TRANSPORT OF WINDS ALOFT DOWN TO THE SURFACE.  THE NOAA AIRCRAFT
REPORTED MAXIMUM FLIGHT-LEVEL WINDS OF 103 KT 100 NMI
NORTH-NORTHEAST OF THE CENTER...BUT SFMR AND DROPSONDE DATA
INDICATE THAT THE SURFACE WINDS IN THAT AREA WERE ONLY AROUND 65
KT.  IN FACT...THERE HAS BEEN NOTHING AT THE SURFACE RECENTLY THAT
QUITE SUPPORTS THE CURRENT 85 KT ADVISORY INTENSITY.  

FORECASTING CHANGES IN THE WIND STRUCTURE OF TROPICAL CYCLONES IS
EVEN MORE CHALLENGING THAN FORECASTING THE INTENSITY...BUT IKE HAS
PLENTY OF TIME FOR ONE OF THE OUTER MAXIMA TO CONTRACT AND FOR THE
WINDS TO TRY TO CATCH UP TO THE CENTRAL PRESSURE...CURRENTLY ABOUT
945 MB.  ALTHOUGH OUTFLOW CONTINUES TO BE RESTRICTED TO THE
NORTHWEST...IT IS STRONG ELSEWHERE AND THE SHEAR IS EXPECTED TO
REMAIN LIGHT.  ONE INHIBITING FACTOR COULD BE UPWELLING/MIXING OF
COOLER WATER AHEAD OF THE PATH OF IKE DUE TO THE UNUSUALLY LARGE
EXPANSE OF STRONG WINDS.  THE OBJECTIVE GUIDANCE NEAR LANDFALL
RANGES FROM A CATEGORY FOUR FROM THE GFDL TO CATEGORY TWO FROM THE
SHIPS MODEL...ABOUT THE ERROR ONE CAN EXPECT FROM AN OFFICIAL
FORECAST ONE TO TWO DAYS OUT.  THE OFFICIAL FORECAST ROUGHLY SPLITS
THE DIFFERENCE BETWEEN THESE GUIDANCE MODELS...AND ANTICIPATES THAT
IKE WILL BE A MAJOR HURRICANE AT LANDFALL.

THE INITIAL MOTION IS 290/9. THERE HAS BEEN LITTLE CHANGE TO THE
TRACK FORECAST THINKING THROUGH LANDFALL...WITH IKE EXPECTED TO
MAINTAIN A WEST-NORTHWESTWARD HEADING UNTIL VERY NEAR
LANDFALL...WHEN IT SHOULD GENTLY TURN TO THE RIGHT AT THE WESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE. THE OFFICIAL FORECAST REMAINS
NEAR THE MODEL CONSENSUS...WITH THE ECMWF ON THE RIGHT AND THE GFS
TO THE LEFT. ONCE AGAIN...GIVEN THE TYPICAL FORECAST ERRORS FOR A
48 HOUR FORECAST...AND THE LARGE SIZE OF THE WIND FIELD...IT IS
IMPORTANT NOT TO FOCUS ON THE EXACT FORECAST TRACK.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/1500Z 25.5N  88.4W    85 KT
 12HR VT     12/0000Z 25.9N  90.0W    90 KT
 24HR VT     12/1200Z 26.6N  92.0W    95 KT
 36HR VT     13/0000Z 27.8N  94.2W   105 KT
 48HR VT     13/1200Z 29.5N  95.9W   100 KT...INLAND
 72HR VT     14/1200Z 34.5N  94.0W    35 KT...INLAND
 96HR VT     15/1200Z 38.0N  85.0W    25 KT...EXTRATROPICAL
120HR VT     16/1200Z...ABSORBED
 
$$
FORECASTER FRANKLIN
 
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