Hurricane IKE

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HURRICANE IKE DISCUSSION NUMBER  43
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL092008
500 PM EDT THU SEP 11 2008
 
A PAIR OF DROPSONDES THIS AFTERNOON IN THE SOUTHEASTERN QUADRANT
FINALLY PROVIDED SOME HARD DATA TO SUPPORT THE ADVISORY
INTENSITY...WITH LOWER-LAYER MEAN WINDS OF 96 KT...WHICH ADJUST TO
80 KT AT THE SURFACE. AIRCRAFT DATA INDICATE THAT THE SMALL INNER
WIND MAXIMUM HAS ALL BUT DISSIPATED...AND THE INNERMOST RADIUS OF
MAXIMUM WINDS IS NOW AROUND 60 NMI. FLIGHT LEVEL WINDS WINDS THERE
ARE ABOUT 100 KT...AND NEARLY THAT STRONG OUT TO AT LEAST 100 NMI.
AS THE INNER WIND MAXIMUM DISSIPATED...THE MINIMUM PRESSURE ROSE TO
ABOUT 954 MB...BUT HAS SINCE FALLEN TO 950 MB.
 
THE INTENSITY GUIDANCE HAS COME DOWN SINCE THIS MORNING...ALTHOUGH
THE GFDL STILL MAKES IKE A MAJOR HURRICANE. FACTORS INHIBITING
DEVELOPMENT INCLUDE THE LARGE BROAD WIND FIELD...STRONG WINDS OVER
AREAS OF LIMITED OCEAN HEAT CONTENT ALONG AND NORTH OF THE PATH OF
IKE...AND AN UPPER-LEVEL RIDGE OVER TEXAS THAT IS FORCING DESCENT
AND CREATING DRY AIR AHEAD OF THE PATH OF THE HURRICANE. INDEED...
CONVECTION ON THE WEST SIDE OF IKE HAS BEEN RATHER THIN FOR MUCH OF
THE DAY. HOWEVER...THIS LATTER UPPER FEATURE IS FORECAST TO SLIDE
NORTHEASTWARD AS IKE ENTERS THE NORTHWESTERN GULF...AND IN THIS
CONFIGURATION WOULD PROVIDE AN UPPER PATTERN MORE CONDUCIVE TO
STRENGTHENING RIGHT BEFORE LANDFALL. CURRENTLY THE OUTFLOW IS VERY
WELL ESTABLISHED TO THE NORTHEAST AND SOUTHWEST OF THE CENTER. THE
OFFICIAL FORECAST IS UNCHANGED FROM THE PREVIOUS ADVISORY AND IS IN
BEST AGREEMENT WITH THE GFDL GUIDANCE.
 
IKE IS MOVING WEST-NORTHWESTWARD AROUND THE PERIPHERY OF A RIDGE OF
HIGH PRESSURE EXTENDING FROM THE WESTERN ATLANTIC WESTWARD OVER THE
SOUTHEASTERN UNITED STATES.  A DEEP LAYER TROUGH CURRENTLY EXTENDS
INTO THE SOUTHWESTERN STATES...AND IKE IS EXPECTED TO GENTLY RECURVE
BETWEEN THESE TWO FEATURES IN 48-72 HOURS.  THE OBJECTIVE GUIDANCE
HAS SHIFTED SLIGHTLY TO THE RIGHT...AND IS RATHER TIGHTLY CLUSTERED
THROUGH LANDFALL.  AS THE UPPER HIGH OVER TEXAS MOVES
NORTHEASTWARD...A SLIGHT BEND OF THE TRACK TO THE LEFT IS EXPECTED
PRIOR TO THE BEGINNING OF RECURVATURE.  THE OFFICIAL FORECAST HAS
BEEN NUDGED SLIGHTLY TO THE RIGHT...BUT IS STILL JUST LEFT OF THE
MODEL CONSENSUS.  IT IS WORTH NOTING THAT THE AVERAGE 36-HOUR
OFFICIAL FORECAST ERROR IS ABOUT 80 NMI.
 
BECAUSE OF THE VERY LARGE EXPANSE OF HURRICANE FORCE WINDS...IKE
WILL CREATE A STORM SURGE WELL IN EXCESS OF WHAT WOULD NORMALLY BE
ASSOCIATED WITH A STORM OF ITS INTENSITY.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/2100Z 26.0N  89.4W    85 KT
 12HR VT     12/0600Z 26.6N  90.9W    90 KT
 24HR VT     12/1800Z 27.6N  93.0W    95 KT
 36HR VT     13/0600Z 29.0N  95.0W   105 KT
 48HR VT     13/1800Z 31.5N  95.5W    65 KT...INLAND
 72HR VT     14/1800Z 37.0N  90.5W    30 KT...INLAND
 96HR VT     15/1800Z...ABSORBED IN FRONTAL ZONE
 
$$
FORECASTER FRANKLIN
 
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