[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 310857
TCDAT2
HURRICANE GUSTAV DISCUSSION NUMBER  27
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072008
500 AM EDT SUN AUG 31 2008

APPARENTLY...THE INTERACTION WITH WESTERN CUBA TOOK MORE OF A TOLL
ON THE HURRICANE THAN EARLIER ESTIMATED. DATA FROM THE AIR FORCE
HURRICANE HUNTER SHOW THAT GUSTAV HAS WEAKENED WITH MAXIMUM
FLIGHT-LEVEL WINDS OF 112 KT...SFMR WINDS OF 98 KT...AND A MINIMUM
CENTRAL PRESSURE OF 958 MB. SATELLITE IMAGES CONFIRM THIS WEAKENING
TREND AS THE EYE NO LONGER VISIBLE. AIRCRAFT AND RADAR OBSERVATIONS
ALSO INDICATE THAT THE EYE HAS EXPANDED TO AROUND 25 N MI IN
DIAMETER. THE INITIAL INTENSITY IS LOWERED TO 110 KT...AND GUSTAV
MAY EVEN BE A LITTLE WEAKER FOR THE MOMENT. HOWEVER THIS WEAKENING
IS FORECAST TO BE SHORT-LIVED AS THE HURRICANE TRAVERSES THE
RELATIVELY HIGH HEAT CONTENT OF THE GULF LOOP CURRENT. BEYOND 24
HOURS...THE HEAT CONTENT DECREASES AND MOST MODELS INCREASE THE
VERTICAL WIND SHEAR NEAR GUSTAV DUE TO AN UPPER-LEVEL LOW OVER THE
WESTERN GULF. IN ADDITION...NONE OF THE NUMERICAL GUIDANCE SHOW
SIGNIFICANT RESTRENGTHENING OF GUSTAV...ALTHOUGH ADMITTEDLY THE
SKILL OF THESE MODELS IS RATHER LOW. THE OFFICIAL INTENSITY
FORECAST IS REDUCED FROM THE EARLIER ONE...BUT STILL SHOWS GUSTAV
AS A MAJOR HURRICANE AT LANDFALL.

BASED UPON AIRCRAFT DATA AND RADAR FIXES FROM KEY WEST...GUSTAV IS
MOVING FASTER TO THE NORTHWEST AND ITS MOTION IS ESTIMATED AT
320/14.  THE LARGE-SCALE STEERING PATTERN APPEARS TO BE
WELL-DEFINED...WITH A RIDGE OVER THE WESTERN ATLANTIC AND
SOUTHEASTERN UNITED STATES PROVIDING A NORTHWESTWARD MOTION TO THE
HURRICANE.  A SLIGHT BEND TO THE LEFT IS ANTICIPATED AS GUSTAV
NEARS THE COAST DUE TO THE TROPICAL CYCLONE COMING UNDER THE
INFLUENCE OF RIDGING OVER THE OHIO VALLEY.  GLOBAL MODELS ARE IN
GOOD AGREEMENT ON THE GENERAL TRACK FORECAST BUT CONTINUE TO SHOW
SOME MINOR DISCREPANCIES IN FORWARD SPEED.  MOST OF THE GUIDANCE
HAS SHIFTED EVER SO SLIGHTLY TO THE EAST...AND THE OFFICIAL
FORECAST IS NUDGED IN THAT DIRECTION.  IT IS IMPORTANT NOT TO FOCUS
ON THE EXACT TRACK OF GUSTAV AS THIS IS A LARGE HURRICANE AND
SIGNIFICANT IMPACTS ARE LIKELY TO OCCUR WELL AWAY FROM THE CENTER.

BASED ON THIS FORECAST...IT IS NOW TIME TO ISSUE A HURRICANE WARNING
FOR THE NORTHERN GULF COAST.

FORECAST POSITIONS AND MAX WINDS

INITIAL      31/0900Z 24.2N  85.0W   110 KT
 12HR VT     31/1800Z 25.6N  86.3W   120 KT
 24HR VT     01/0600Z 27.5N  88.4W   125 KT
 36HR VT     01/1800Z 29.1N  90.4W   115 KT...NEAR COAST
 48HR VT     02/0600Z 30.5N  92.2W    75 KT...INLAND
 72HR VT     03/0600Z 31.7N  93.7W    30 KT...INLAND
 96HR VT     04/0600Z 32.0N  94.5W    25 KT...INLAND
120HR VT     05/0600Z 32.0N  95.5W    20 KT...INLAND

$$
FORECASTER BLAKE/PASCH



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