[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 311457
TCDAT2
HURRICANE GUSTAV DISCUSSION NUMBER  28
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072008
1100 AM EDT SUN AUG 31 2008

GUSTAV CONTINUES TO LOOK SOMEWHAT RAGGED IN SATELLITE APPEARANCE
THIS MORNING.  THE DEEP CONVECTION IS VERY ASYMMETRIC...WITH THE
COLD TOPS DUE MAINLY TO ONE HOT TOWER IN THE WESTERN EYEWALL.
WHILE AN EYE-LIKE FEATURE IS APPARENT...IT IS DISPLACED TO THE
NORTHEAST OF THE AIRCRAFT-REPORTED CENTER.  THE LATEST REPORT FROM
A NOAA HURRICANE HUNTER INDICATES THE CENTRAL PRESSURE HAS RISEN TO
962 MB...ALONG WITH AN ELLIPTICAL 30 BY 20 N MI WIDE EYE OPEN TO THE
SOUTHEAST.  THE INITIAL INTENSITY IS REDUCED TO 105 KT...AND THIS
MIGHT BE A LITTLE GENEROUS BASED ON THE AIRCRAFT WINDS.

THE INITIAL MOTION IS 320/15.  THERE IS NO CHANGE IN THE FORECAST
PHILOSOPHY FOR THE EARLY PORTION OF THE FORECAST TRACK...WITH A
MID-LEVEL RIDGE OVER THE EASTERN UNITED STATES EXPECTED TO STEER
GUSTAV NORTHWESTWARD INTO THE NORTHERN GULF COAST.  THE NEW
GUIDANCE RUNS SHOW A SLIGHT LEFT TURN AFTER 12 HR WITH A LEFTWARD
SHIFT IN THE LANDFALL POINT ON THE LOUISIANA COAST.  THE NEW
FORECAST TRACK WILL NOT FOLLOW THIS SHIFT YET...AND THUS LIES NEAR
THE EASTERN EDGE OF THE GUIDANCE ENVELOPE AND THE PREVIOUS FORECAST
TRACK THROUGH 48 HR.  AFTER 48-72 HR...THERE IS MAJOR DISAGREEMENT
BETWEEN THE DYNAMICAL MODELS ON WHETHER GUSTAV WILL RECURVE INTO
THE WESTERLIES...STALL OVER LOUISIANA OR TEXAS...OR TURN
SOUTHWESTWARD.  SINCE THIS KIND OF SPREAD FREQUENTLY PRECEDES SLOW
MOTION...THE FORECAST TRACK WILL CALL FOR A SLOW WESTWARD MOTION
AFTER 72 HR.

AT THE RISK OF SOUNDING LIKE A BROKEN RECORD...THE INTENSITY
FORECAST REMAINS PROBLEMATIC.  ANALYSES FROM CIMSS AT THE
UNIVERSITY OF WISCONSIN SHOWS THAT GUSTAV REMAINS IN 15 TO 20 KT OF
SOUTHERLY VERTICAL SHEAR....AND THE LARGE-SCALE MODELS FORECAST AT
LEAST SOME SOUTHERLY TO SOUTHWESTERLY SHEAR TO PERSIST UNTIL
LANDFALL.  THAT...COMBINED WITH THE CURRENT RAGGED STORM STRUCTURE
AND THE MID-LEVEL DRY AIR TRYING TO WRAP AROUND THE STORM IN WATER
VAPOR IMAGERY...SUGGESTS ANY INTENSIFICATION SHOULD BE SLOW.
ADDITIONALLY..GUSTAV IS OVER A WARM EDDY IN THE LOOP CURRENT
NOW...AND SHOULD PASS OVER WATERS WITH LOWER OCEANIC HEAT CONTENT
BETWEEN NOW AND LANDFALL.  THE GUIDANCE RESPONDS TO THESE FACTORS
BY FORECASTING MODEST STRENGTHENING DURING THE NEXT 12 TO 24
HR...WITH THE GFDL FORECASTING A PEAK INTENSITY OF 120 KT AND THE
OTHER MODELS ABOUT 110 KT.  BASED ON THIS...THE INTENSITY FORECAST
WILL CALL FOR GUSTAV TO RE-INTENSIFY TO 115 KT IN 12 TO 24 HR...AND
MAKE LANDFALL ON THE NORTHERN GULF COAST AS A MAJOR HURRICANE.
GUSTAV SHOULD STEADILY WEAKEN AFTER LANDFALL.

FORECAST POSITIONS AND MAX WINDS

INITIAL      31/1500Z 25.3N  86.0W   105 KT
 12HR VT     01/0000Z 27.0N  87.7W   115 KT
 24HR VT     01/1200Z 28.6N  89.7W   115 KT
 36HR VT     02/0000Z 30.0N  91.5W    85 KT...INLAND
 48HR VT     02/1200Z 31.1N  93.0W    50 KT...INLAND
 72HR VT     03/1200Z 32.0N  94.5W    30 KT...INLAND
 96HR VT     04/1200Z 32.0N  95.0W    25 KT...INLAND
120HR VT     05/1200Z 32.0N  95.9W    20 KT...INLAND REMNANT LOW

$$
FORECASTER BEVEN




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