[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 010257
TCDAT2
HURRICANE GUSTAV DISCUSSION NUMBER  30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072008
1100 PM EDT SUN AUG 31 2008

THE SATELLITE PRESENTATION OF GUSTAV BECAME MORE SYMMETRIC EARLIER
IN THE EVENING AND WAS GIVING THE IMPRESSION OF INCREASING
ORGANIZATION. OVER THE PAST HOUR OR SO...HOWEVER...THERE HAS BEEN
SLIGHT WARMING OF THE CORE CONVECTION IN THE EASTERN SEMICIRCLE.
THE CENTRAL PRESSURE...WHICH HAD BEEN FALLING...SEEMS TO HAVE
STABILIZED WITH THE MOST RECENT ESTIMATE BEING 954 MB. FLIGHT LEVEL
AND SFMR DATA INDICATE THAT THE MAXIMUM SURFACE WINDS ARE STILL
AROUND 100 KT...WITH A PEAK SMFR WIND OF 100 KT JUST OBSERVED A FEW
MINUTES AGO...AND PEAK FLIGHT LEVEL WINDS OF 114 KT. THE SFMR DATA
ALSO INDICATE THAT THE HURRICANE FORCE WINDS HAVE EXPANDED...
SPREADING OUT THE PRESSURE GRADIENT OVER A LARGER AREA.  DROPSONDE
DATA FROM THE NOAA G-IV JET AIRCRAFT ALSO SHOW SOME DRIER AIR
BETWEEN 300 AND 500 MB WORKING ITS WAY TOWARD THE CENTER OF GUSTAV
FROM THE SOUTH.  THESE DATA SUGGEST THAT THE LANDFALL INTENSITY OF
GUSTAV WILL LIKELY BE NOT VERY DIFFERENT FROM ITS CURRENT CATEGORY
THREE STRENGTH.  NONE OF THE AVAILABLE OBJECTIVE AIDS...THE
GFDL...HWRF...SHIPS...AND LGEM SHOW MUCH CHANGE IN THE REMAINING
TIME GUSTAV HAS OVER WATER.

THE INITIAL MOTION IS 315/14.  THERE HAS BEEN NO CHANGE TO THE TRACK
FORECAST PHILOSOPHY THAT SHOWS GUSTAV MOVING NORTHWESTWARD BETWEEN
A MID- TO UPPER-LEVEL LOW IN THE WESTERN GULF OF MEXICO AND
MID-LEVEL HIGH PRESSURE OVER THE OHIO VALLEY.  MODEL GUIDANCE IS
VERY TIGHTLY CLUSTERED AROUND THE PREVIOUS OFFICIAL FORECAST
THROUGH 48 HOURS AND THE NEW FORECAST IS JUST ABOUT RIGHT ON TOP OF
THE PREVIOUS ONE.  AFTER THAT...AS SOUTHWESTERLY SHEAR IS FORECAST
TO INCREASE...THE MODELS DIVERGE SHARPLY.  AS BEFORE...THE OFFICIAL
FORECAST CALLS FOR LITTLE MOTION AFTER 72 HOURS IN THE EXPECTATION
THAT GUSTAV WILL SHEAR OFF...IN GOOD AGREEMENT WITH THE SHALLOW BAM.

FORECAST POSITIONS AND MAX WINDS

INITIAL      01/0300Z 27.3N  88.1W   100 KT
 12HR VT     01/1200Z 28.6N  89.9W   105 KT
 24HR VT     02/0000Z 30.1N  91.9W    85 KT...INLAND
 36HR VT     02/1200Z 31.1N  93.3W    50 KT...INLAND
 48HR VT     03/0000Z 31.8N  94.3W    30 KT...INLAND
 72HR VT     04/0000Z 32.0N  95.0W    25 KT...INLAND
 96HR VT     05/0000Z 32.0N  95.5W    25 KT...INLAND
120HR VT     06/0000Z 32.0N  96.0W    20 KT...REMNANT LOW

$$
FORECASTER FRANKLIN

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