ATTENTION COASTAL STATES BORDERING THE GULF OF MEXICO
000
WTNT42 KNHC 280904
TCDAT2
TROPICAL STORM GUSTAV DISCUSSION NUMBER 13
NWS
TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072008
500 AM EDT THU AUG 28 2008
AN
AIR FORCE RECONNAISSANCE PLANE HAS FOUND A SURPRISE THIS MORNING. GUSTAV HAS EITHER REFORMED TO THE SOUTH OR BEEN MOVING MORE
TO THE SOUTH-SOUTHWEST OVERNIGHT. IN ADDITION ... THE PRESSURE IS DOWN 10 MB DURING THE LAST SIX HOURS. THE PLANE HAS NOT
YET SAMPLED THE ENTIRE STORM...BUT IT IS ASSUMED THE WINDS HAVE COME UP SLIGHTLY WITH THE SIGNIFICANT PRESSURE FALL AND THE
INITIAL INTENSITY IS INCREASED TO 45 KT. MID-LEVEL DRY AIR...SOME NORTHEASTERLY SHEAR...AND INTERACTION WITH JAMAICA MAY LIMIT
THE INTENSIFICATION OF THIS SYSTEM DURING THE NEXT DAY OR SO. THUS THE OFFICIAL INTENSITY FORECAST IS ONLY SLIGHTLY RAISED
FROM EARLIER. THEREAFTER...THE GLOBAL MODELS ARE FORECASTING AN UPPER ANTICYCLONE TO BE NEAR THE CENTER OF GUSTAV...WHICH
WOULD BE QUITE FAVORABLE FOR STRENGTHENING. IT IS EXPECTED THAT GUSTAV WILL BE A POWERFUL HURRICANE AS IT MOVES INTO
THE SOUTHERN GULF OF MEXICO ON SUNDAY. SOUTHWESTERLY VERTICAL WIND SHEAR COULD INCREASE LATE IN THE PERIOD WHEN THE SYSTEM
IS FORECAST TO BE IN THE NORTHERN GULF BUT THERE IS CONSIDERABLY UNCERTAINTY AT THAT TIME.
THE BEST ESTIMATE OF INITIAL MOTION IS 215/7. THE REFORMATION OF THE CENTER HAS CAUSED
A BIG SOUTHWARD CHANGE IN THE EARLY PART OF THE FORECAST...AND GUSTAV IS NOW FORECAST TO PASS NEAR THE SOUTH COAST OF JAMAICA.
THE NORTHEAST-SOUTHWEST ORIENTED RIDGE CENTERED OVER THE FLORIDA PENINSULA THAT HAS BEEN CAUSING THIS SOUTHWESTWARD MOTION
IS EXPECTED TO WEAKEN OVER THE NEXT FEW DAYS. THIS SHOULD ALLOW GUSTAV TO TURN MORE TO THE WEST AND THEN NORTHWEST AROUND
THE TIME IT ENTERS THE GULF OF MEXICO. A MID-LATITUDE HIGH IS FORECAST
TO BE IN THE OHIO VALLEY IN ABOUT 5 DAYS...WHICH
MAY CONTINUE STEERING THE STORM IN A NORTHWESTWARD FASHION RATHER THAN ALLOW A MORE NORTHWARD MOTION LIKE THE GFDL SUGGESTS.
THE OFFICIAL FORECAST IS SHIFTED WESTWARD IN THE LONGER-TERM...ON THE EASTERN SIDE OF THE MODEL GUIDANCE ENVELOPE...BUT THE
ECMWF AND GFDL ARE TO THE RIGHT OF THE NHC FORECAST.
FORECAST POSITIONS AND MAX WINDS
INITIAL
28/0900Z 17.8N 75.6W 45 KT
12HR VT 28/1800Z 17.5N 77.0W
55 KT
24HR VT 29/0600Z 17.8N 78.5W 60 KT
36HR VT
29/1800Z 18.5N 80.3W 65 KT
48HR VT 30/0600Z 19.5N 82.0W
75 KT
72HR VT 31/0600Z 22.0N 85.5W 95 KT
96HR VT
01/0600Z 26.0N 89.0W 100 KT
120HR VT 02/0600Z 28.5N 91.0W 100
KT
$$
FORECASTER BLAKE/AVILA