Tropical Storm Gustav: Forecast Discussion #10

TROPICAL STORM GUSTAV DISCUSSION NUMBER 10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008
1100 AM EDT WED AUG 27 2008

GUSTAV HAS BEEN SLOW TO DEPART THE SOUTHWEST PENINSULA OF HAITI.
HOWEVER RECENT HIGH-RESOLUTION VISIBLE SATELLITE IMAGES AND RADAR
OBSERVATIONS FROM GRAN PIEDRA CUBA SUGGEST THAT THE TROPICAL
CYCLONE IS GRADUALLY BECOMING BETTER ORGANIZED. THE LAST AERIAL
RECONNAISSANCE OBSERVATIONS IN THE STORM DID NOT ACTUALLY SUPPORT
AN INTENSITY OF 50 KT...BUT BASED ON THE TREND SEEN IN THE
SATELLITE PRESENTATION WE ASSUME THAT GUSTAV IS PROBABLY VERY NEAR
THAT INTENSITY BY NOW. CIRRUS MOTIONS INDICATE SOME MODEST
NORTHERLY SHEAR OVER THE SYSTEM BUT OTHERWISE THE ENVIRONMENT SEEMS
TO BE FAVORABLE FOR STRENGTHENING...ONCE GUSTAV PULLS AWAY FROM
HAITI. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS
ONE THROUGH DAY 3. GLOBAL MODELS SHOW SOME INCREASE IN
SOUTHWESTERLY SHEAR AT DAYS 4 AND 5... SO WE SHOW LITTLE CHANGE IN
STRENGTH IN THE LATTER PART OF THE FORECAST PERIOD.
NOTWITHSTANDING...THERE IS VERY LITTLE...IF ANY...SKILL IN
INTENSITY PREDICTIONS AT THESE EXTENDED RANGES. INDEED...IF ONE
LOOKS AT THE LATEST WIND SPEED PROBABILITY PRODUCT INCLUDED IN THIS
PACKAGE...IT CAN BE SEEN THAT THERE IS NEARLY AN EQUAL CHANCE THAT
GUSTAV WILL BE A CATEGORY 1...CATEGORY 2...OR CATEGORY 3 HURRICANE
AT THE END OF THE FORECAST PERIOD.

THE CENTER HAS BEEN WOBBLING AS IT INTERACTED WITH THE MOUNTAINOUS
LANDMASS OF SOUTHWESTERN HAITI. HOWEVER A SLOW WEST-NORTHWESTWARD
MOTION...290/4...APPEARS TO HAVE RESUMED THIS MORNING. A 500 MB
HIGH CENTERED NEAR FLORIDA WITH AN ASSOCIATED RIDGE EXTENDING
EASTWARD AND WESTWARD IS EXPECTED TO DRIVE THE STORM TOWARD THE
WEST OR WEST-NORTHWEST OVER THE NEXT COUPLE OF DAYS. BEGINNING
AROUND DAY 3...THE GLOBAL MODELS SHOW SOME WEAKENING OF THE THE
RIDGE OVER THE EAST-CENTRAL GULF OF MEXICO. THIS SHOULD CAUSE
GUSTAV TO GRADUALLY TURN TOWARD THE NORTHWEST IN 4 TO 5 DAYS. THE
OFFICIAL FORECAST IS VERY SIMILAR TO THE PREVIOUS NHC TRACK THROUGH
72 HOURS AND IS SHIFTED A LITTLE TO THE RIGHT BY DAY 5. ONE SHOULD
NOT READ MUCH INTO SUCH SHIFTS OF THE FORECAST TRACK SINCE THE
TYPICAL ERROR OF A 5-DAY PREDICTION IS OVER 300 MILES.

FORECAST POSITIONS AND MAX WINDS

INITIAL 27/1500Z 18.8N 74.0W 50 KT
12HR VT 28/0000Z 19.0N 74.8W 55 KT
24HR VT 28/1200Z 19.2N 76.0W 60 KT
36HR VT 29/0000Z 19.3N 77.5W 70 KT
48HR VT 29/1200Z 19.9N 79.4W 80 KT
72HR VT 30/1200Z 21.5N 83.0W 100 KT
96HR VT 31/1200Z 24.5N 86.0W 100 KT
120HR VT 01/1200Z 28.5N 88.5W 100 KT


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