[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 312052
TCDAT2
HURRICANE GUSTAV DISCUSSION NUMBER  29
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072008
500 PM EDT SUN AUG 31 2008

VISIBLE SATELLITE IMAGERY DURING THE PAST COUPLE OF HOURS SUGGESTS
THAT GUSTAV IS GETTING A LITTLE BETTER ORGANIZED...WITH A HINT OF
AN EYE RETURNING.  ADDITIONALLY...THE CENTRAL PRESSURE REPORTED BY
AN AIR FORCE RESERVE HURRICANE HUNTER HAS FALLEN TO 957 MB.  ON THE
OTHER HAND...THE MAXIMUM 700 MB FLIGHT-LEVEL WINDS WERE 105 KT WHILE
THE MAXIMUM SFMR WINDS WERE 93 KT.  ALSO...THE CONVECTION...WHILE
VIGOROUS...IS STILL RATHER ASYMMETRIC AROUND THE 30 NM WIDE EYE
THAT IS OPEN TO THE SE.  BASED ON THE AIRCRAFT DATA...THE INITIAL
INTENSITY IS LOWERED TO 100 KT.

THE INITIAL MOTION IS WOBBLING BETWEEN 315 AND 320 DEGREES AT 15-16
KT...WITH 320/16 BEING THE ADVISORY MOTION.  THERE IS NO CHANGE IN
THE TRACK FORECAST PHILOSOPHY...WITH A
MID-LEVEL RIDGE OVER THE EASTERN UNITED STATES EXPECTED TO STEER
GUSTAV NORTHWESTWARD INTO THE NORTHERN GULF COAST.  THE NEW
GUIDANCE RUNS...MOST NOTABLY THE HWRF...SHOW A SLIGHT LEFT TURN
AFTER 12 HR WITH A LEFTWARD SHIFT IN THE LANDFALL POINT ON THE
LOUISIANA COAST.  THE NEW FORECAST TRACK IS SHIFTED SLIGHTLY TO THE
LEFT OF THE PREVIOUS TRACK...AND SINCE IT LIES NEAR THE EASTERN
EDGE OF THE GUIDANCE ENVELOPE SOME ADDITIONAL SMALL SHIFTS MAY BE
NECESSARY LATER.  AFTER 48-72 HR...THERE REMAINS MAJOR DISAGREEMENT
BETWEEN THE DYNAMICAL MODELS ON WHETHER GUSTAV WILL RECURVE INTO
THE WESTERLIES...SHEAR APART AND STALL OVER LOUISIANA OR TEXAS...OR
TURN SOUTHWESTWARD.  THE FORECAST TRACK AFTER 72 HR FOLLOWS THE
SHEAR-APART-AND-STALL SCENARIO...CALLING FOR GUSTAV TO MOVE SLOWLY
WESTWARD AS IT WEAKENS OVER LAND.

ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATE THAT
GUSTAV REMAINS IN ABOUT 20 KT OF SOUTHERLY SHEAR...WITH A LOT OF
MID/UPPER-LEVEL DRY AIR SEEN IN WATER VAPOR IMAGERY SOUTH AND WEST
OF THE CYCLONE.  THE EYE HAS MOVED NORTHWEST OF THE DEEP WARM WATER
OF THE LOOP CURRENT...AND THAT COMBINED WITH THE LIKELIHOOD OF
CONTINUED SHEAR REDUCES THE CHANCES OF SIGNIFICANT INTENSIFICATION.
THE SHIPS MODEL FORECASTS NO STRENGTHENING BEFORE LANDFALL...WHILE
THE GFDL AND HWRF FORECAST ABOUT 10 KT OF STRENGTHENING.  GIVEN THE
FALLING PRESSURES AND THE COLD CONVECTION...THE INTENSITY FORECAST
CALLS FOR WINDS TO INCREASE TO 110 KT BEFORE LANDFALL...WITH GUSTAV
MAKING LANDFALL AS A MAJOR HURRICANE.  GUSTAV SHOULD WEAKEN AFTER
LANDFALL AND BECOME A REMNANT LOW IN ABOUT 120 HR.


FORECAST POSITIONS AND MAX WINDS

INITIAL      31/2100Z 26.4N  87.3W   100 KT
 12HR VT     01/0600Z 27.9N  88.9W   110 KT
 24HR VT     01/1800Z 29.4N  90.9W   100 KT...INLAND
 36HR VT     02/0600Z 30.7N  92.7W    60 KT...INLAND
 48HR VT     02/1800Z 31.5N  93.9W    35 KT...INLAND
 72HR VT     03/1800Z 32.0N  95.0W    30 KT...INLAND
 96HR VT     04/1800Z 32.0N  96.0W    25 KT...INLAND
120HR VT     05/1800Z 32.0N  96.5W    20 KT...INLAND REMNANT LOW

$$
FORECASTER BEVEN



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