Hurricane GUSTAV

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HURRICANE GUSTAV DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072008
1100 PM EDT SAT AUG 30 2008
 
THE EYE OF GUSTAV CROSSED WESTERN CUBA DURING THE PAST SEVERAL
HOURS AND IS NOW OVER THE SOUTHEASTERN GULF OF MEXICO.  THE
HURRICANE WEAKENED DURING PASSAGE OVER LAND...WITH THE EYE BECOMING
CLOUD FILLED AND THE EYEWALL CONVECTION BECOME LESS IMPRESSIVE IN
BOTH SATELLITE AND RADAR DATA.  IT IS ESTIMATED THAT THE INITIAL
INTENSITY HAS DECREASED TO 120 KT.  AN AIR FORCE RESERVE HURRICANE
HUNTER AIRCRAFT WILL ARRIVE IN THE STORM ABOUT 06Z TO DETERMINE THE
ACTUAL INTENSITY.

THE MOTION HAS BEEN WOBBLING BETWEEN 315 AND 320 DEGREES AT 13
KT...WITH 320/13 USED IN THIS PACKAGE.  THERE IS NO CHANGE IN THE
SYNOPTIC REASONING...WITH GUSTAV BEING STEERED NORTHWESTWARD BY A
MID-LEVEL RIDGE OVER THE SOUTHEASTERN UNITED STATES...AND THEN BY
AN AMPLIFYING MID-LEVEL RIDGE OVER THE EASTERN UNITED STATES.  THE
TRACK GUIDANCE IS TIGHTLY CLUSTERED THROUGH 72 HR...CALLING FOR
GUSTAV TO TRACK ACROSS THE GULF OF MEXICO AND MAKE LANDFALL IN
SOUTHEASTERN OR SOUTH CENTRAL LOUISIANA.  THE NEW FORECAST TRACK
FOLLOWS THIS SCENARIO IS LIES JUST TO THE EAST OF THE PREVIOUS
TRACK.  AFTER LANDFALL...THE DYNAMICAL MODELS DISAGREE ON HOW MUCH
MID-LEVEL RIDGING WILL DEVELOP NORTH AND WEST OF GUSTAV...WITH A
CONSIDERABLE SPREAD IN THE GUIDANCE.  THE TRACK FORECAST AT THAT
TIME CALLS FOR A SLOW WESTWARD MOTION.  IT SHOULD BE NOTED THAT THE
12Z UKMET FORECASTS GUSTAV TO TURN SOUTHWESTWARD AS IT REACHES THE
LOUISIANA COAST...WHICH APPEARS UNLIKELY AT THIS TIME.

THE INTENSITY FORECAST REMAINS PROBLEMATIC.  ANALYSES FROM CIMSS AT
THE UNIVERSITY OF WISCONSIN SUGGEST THAT THE INTENSIFICATION
OCCURRED DESPITE ABOUT 20 KT OF SOUTHERLY VERTICAL SHEAR CAUSED BY
AN UPPER-LEVEL TROUGH OVER THE GULF OF MEXICO.  THE PRESENCE OF
THIS SHEAR IS SUPPORTED BY RADAR DATA FROM THE KEY WEST WSR-88D...
WHICH CURRENTLY SHOWS A WEAK SOUTHERN EYEWALL AND LITTLE
PRECIPITATION SOUTH OF THE EYEWALL.  THE SHIPS MODEL SUGGESTS THE
SHEAR SHOULD DIMINISH SOME DURING THE NEXT 18 HR...THEN INCREASE
AGAIN AS GUSTAV MOVES BETWEEN THE TROUGH AND AN UPPER-LEVEL
ANTICYCLONE TO THE SOUTHEAST.  ON THE OCEAN SIDE...GUSTAV IS
FORECAST TO PASS OVER THE LOOP CURRENT DURING THE NEXT 24 HOURS...
THEN POSSIBLY PASS OVER A COUPLE OF COLD EDDIES NORTH OF 26N.  ALL
GUIDANCE FORECAST RE-INTENSIFICATION DURING THE NEXT 24 HR...SO THE
INTENSITY FORECAST WILL CALL FOR A PEAK INTENSITY OF 135 KT IN 24
HR...FOLLOWED BY SLIGHT WEAKENING BEFORE LANDFALL DUE TO SHEAR AND
LOWER HEAT CONTENT...THEN FASTER WEAKENING OVER LAND.  DUE TO THE
VARIOUS FACTORS...THIS IS A LOW CONFIDENCE INTENSITY FORECAST.
 
HURRICANE WARNINGS WILL LIKELY BE REQUIRED FOR PORTIONS FOR THE
NORTHERN GULF COAST ON THE NEXT ADVISORY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      31/0300Z 23.1N  83.8W   120 KT
 12HR VT     31/1200Z 24.6N  85.3W   130 KT
 24HR VT     01/0000Z 26.5N  87.4W   135 KT
 36HR VT     01/1200Z 28.3N  89.5W   130 KT
 48HR VT     02/0000Z 29.8N  91.2W   120 KT...INLAND
 72HR VT     03/0000Z 31.5N  93.0W    50 KT...INLAND
 96HR VT     04/0000Z 32.5N  94.5W    30 KT...INLAND
120HR VT     05/0000Z 32.5N  96.0W    25 KT...INLAND
 
$$
FORECASTER BEVEN
 
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