Hurricane Gustav: Forecast Discussion #7

HURRICANE GUSTAV DISCUSSION NUMBER 7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008
500 PM EDT TUE AUG 26 2008

AIR FORCE HURRICANE HUNTER REPORTS AND VISIBLE SATELLITE IMAGES...ON
WHICH THE EYE OF THE HURRICANE BECAME EVIDENT...INDICATE THAT THE
CENTER OF GUSTAV MADE LANDFALL AROUND 1730 UTC. A MINIMUM PRESSURE
OF 992 MB WAS REPORTED BY THE AIRCRAFT JUST AS THE CENTER MOVED
INLAND...HOWEVER A DROPSONDE RELEASED JUST EAST OF THE EYE HAD A
SURFACE PRESSURE OF 997 MB WITH SOUTHERLY WINDS OF 64 KT. SO THE
CENTRAL PRESSURE MAY HAVE BEEN SOMEWHAT LOWER THAN 992 MB. IN ANY
EVENT...NOW THAT THE CENTER IS MOVING OVER THE MOUNTAINOUS TERRAIN
OF THE SOUTHWEST PENINSULA OF HAITI...GUSTAV IS LIKELY LOSING
STRENGTH. THE EYE IS NO LONGER EVIDENT ON SATELLITE IMAGES...AND
THE SYSTEM COULD WEAKEN BELOW HURRICANE INTENSITY TONIGHT. HOWEVER
THE UPPER-LEVEL ENVIRONMENT REMAINS FAVORABLE FOR INTENSIFICATION
WITH ONLY A LITTLE NORTH-NORTHEASTERLY SHEAR...AND THEREFORE GUSTAV
IS LIKELY TO REGAIN STRENGTH AS IT APPROACHES THE WINDWARD PASSAGE
AND EASTERN CUBA TOMORROW. THE OFFICIAL INTENSITY FORECAST IS A
BLEND OF THE SHIPS...LGEM...HWRF...AND GFDL GUIDANCE AND IS VERY
SIMILAR TO THE PREVIOUS NHC WIND SPEED FORECAST. IT SHOULD BE
RECALLED THAT BOTH SUBJECTIVE AND MODEL FORECASTS OF INTENSITY HAVE
LITTLE SKILL IN THE 3- TO 5-DAY RANGE.

INITIAL MOTION IS AROUND 305/9. THE MAIN PLAYER IN THE STEERING
PATTERN FOR GUSTAV CONTINUES TO BE A MID-TROPOSPHERIC
ANTICYCLONE/HIGH CENTERED NEAR THE FLORIDA PENINSULA. THE TROPICAL
CYCLONE'S HEADING SHOULD GRADUALLY BEND TOWARD THE LEFT AS IT MOVES
ALONG THE SOUTHERN PERIPHERY OF THIS ANTICYCLONE. LATER IN THE
FORECAST PERIOD...GUSTAV IS EXPECTED TO TURN TOWARD THE NORTHWEST
AS IT ROUNDS THE SOUTHWESTERN PERIPHERY OF THE HIGH. THE TRACK
GUIDANCE MODELS ARE IN PRETTY GOOD AGREEMENT ON A GRADUAL TURN
TOWARD THE WEST-NORTHWEST OVER THE NEXT DAY OR SO...AND OVERALL THE
MODEL CONSENSUS HAS CHANGED LITTLE FROM THE PREVIOUS ADVISORY
PACKAGE. THEREFORE THE TRACK FORECAST FOR THIS ADVISORY IS
ESSENTIALLY AN EXTENSION OF THE PREVIOUS ONE.

FORECAST POSITIONS AND MAX WINDS

INITIAL 26/2100Z 18.4N 73.2W 65 KT
12HR VT 27/0600Z 18.9N 74.0W 75 KT
24HR VT 27/1800Z 19.3N 75.2W 80 KT
36HR VT 28/0600Z 19.5N 76.6W 85 KT
48HR VT 28/1800Z 19.6N 78.0W 90 KT
72HR VT 29/1800Z 20.3N 81.0W 100 KT
96HR VT 30/1800Z 22.5N 85.0W 105 KT
120HR VT 31/1800Z 25.5N 88.5W 105 KT


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