HURRICANE IKE

HURRICANE IKE DISCUSSION NUMBER 17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092008
500 AM EDT FRI SEP 05 2008

THE EYE OF IKE HAS LOST A LITTLE OF ITS DEFINITION...AND CLOUD TOPS
OF THE EYEWALL HAVE WARMED SOMEWHAT. DVORAK T-NUMBERS HAVE COME
DOWN SLIGHTLY AND THE INITIAL INTENSITY IS SET TO 110 KT.
MICROWAVE IMAGERY JUST RECEIVED FROM THE AMSR-E DOES NOT REVEAL ANY
SIGNIFICANT DETERIORATION OF THE INNER CORE STRUCTURE...NOR DOES IT
DEPICT CONCENTRIC EYEWALLS...SO RAPID WEAKENING DOES NOT APPEAR TO
BE ABOUT TO OCCUR. THAT IMAGERY DOES SHOW SOME EROSION OF THE
NORTHWESTERN EYEWALL...AND GIVEN THE NORTHEASTERLY SHEAR...THE
OFFICIAL FORECAST CALLS FOR SOME WEAKENING IN THE SHORT TERM.
GLOBAL MODELS FORECAST THE SHEAR TO LESSEN BEYOND 24 HOURS...AS IKE
REMAINS OVER WATERS NEAR 29 CELSIUS...SO RESTRENGTHENING IS THEN
FORECAST. THE HWRF FORECASTS IKE TO BE A MAJOR HURRICANE AT DAYS
3-5...BUT THE GFDL DOES NOT SINCE ITS TRACK GOES OVER CUBA.
MEANWHILE THE SHIPS AND LGEM FORECAST A WEAKER HURRICANE...ALTHOUGH
THE LGEM PREDICTION APPEARS MORE REALISTIC SINCE IT DOES A BETTER
JOB OF TAKING INTO ACCOUNT THE EVENTUAL LESSENING OF THE SHEAR.
SINCE THE OFFICIAL FORECAST TRACK REMAINS OVER WATER THROUGH 96
HOURS...A BLEND OF THE HWRF AND LGEM SEEMS TO BE REASONABLE...AND
IKE IS FORECAST TO BE A MAJOR HURRICANE AT LONGER RANGES. THE ONLY
REASON FOR THE WEAKENING AT THE END IS THAT THE FIVE-DAY POINT IS
OVER LAND...WHICH IS NOT A CERTAINTY.

THE MID-LEVEL RIDGE HAS SETTLED IN DIRECTLY NORTH OF IKE...AS THE
HIGH-LATITUDE TROUGH DEPARTS ATLANTIC CANADA...AND THE HURRICANE IS
NOW HEADED DUE WESTWARD OR 270/13. NEXT TO DEPART THE WESTERN
ATLANTIC SCENE WILL BE HANNA...AND ALL DYNAMICAL MODELS SAY THAT IN
ITS PLACE THE RIDGE WILL EXTEND SOUTHWESTWARD TO FLORIDA IN A
COUPLE OF DAYS. A KEY UNKNOWN FOR THE 3-5 DAY FORECAST IS HOW
STRONG THAT RIDGE WILL BE AND HOW LONG IT WILL REMAIN INTACT. IN
GENERAL DURING THE LAST DAY OR TWO THE MODELS HAVE BEEN TRENDING
TOWARD THE RIDGE STAYING IN PLACE LONGER...RESULTING IN TRACKS
MAINTAINING THE GENERALLY WESTWARD MOTION LONGER AND DELAYING ANY
POTENTIAL TURN TO THE NORTH. THAT TREND HAS CONTINUED SOMEWHAT ON
THIS CYCLE...BUT THE CONSENSUS HAS ONLY SHIFTED WEST SLIGHTLY AT
DAYS 4 AND 5. THE NEW OFFICIAL TRACK FORECAST IS ALMOST IDENTICAL
TO THE PREVIOUS ONE THROUGH 72 HOURS...IS JUST NUDGED TOWARD THE
CONSENSUS BEYOND THAT TIME...AND GIVES THE MOST WEIGHT TO THE GFS
AND HWRF. IT CANNOT BE SAID ENOUGH THAT FIVE-DAY TRACK FORECASTS
CAN HAVE SIGNIFICANT ERRORS...AND COMBINED WITH THE FACT THAT THE
MODEL SPREAD IS STILL NOTABLE BEYOND 72 HOURS...ONE SHOULD NOT
FOCUS ON THE EXACT TRACK.