HOME	ARCHIVES	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

ZCZC MIATCDAT3 ALL
TTAA00 KNHC DDHHMM
SUBTROPICAL STORM GUSTAV DISCUSSION NUMBER   3
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT SUN SEP 08 2002
 
GUSTAV CONTINUES TO GET BETTER ORGANIZED AND IS BEGINNING TO LOOK 
MORE TROPICAL-LIKE. A LARGE BURST OF DEEP CONVECTION HAS DEVELOPED 
JUST NORTH OF THE LOW-LEVEL CENTER...WHILE OTHER MODERATE CONVECTION 
HAS DEVELOPED SOUTHWEST AND SOUTHEAST OF THE CENTER. ANTICYCLONIC 
OUTFLOW HAS ALSO BECOME BETTER DEFINED IN ALL BUT THE EASTERN 
QUADRANT. THE LONG BAND OF MULTI-LAYERED CLOUDINESS AND CONVECTION 
TO THE EAST HAS BEGUN TO SEPARATE AND MOVE AWAY FROM THE MAIN 
CIRCULATION...FURTHER SUGGESTING THAT GUSTAV IS TRYING TO TRANSITION 
OVER TO A PURE WARM-CORE TROPICAL CYCLONE. THE INITIAL INTENSITY OF 
40 KT IS BASED ON A BLEND OF SUBTROPICAL SATELLITE INTENSITY 
ESTIMATES OF ST3.0...OR 45 KT FROM TAFB AND ST2.5 PLUS...OR 40 KT 
FROM SAB...ALONG WITH THE LAST RECON PRESSURE REPORT INDICATING 
ANOTHER 1 MB DROP. A 08/2238Z THAT JUST CAME IN ALSO CONFIRMED THE 
ADVISORY POSITION AND ALSO SHOWED A LARGE FIELD OF 35 KT WINDS IN 
THE CLEAR SLOT TO THE NORTHEAST. STRONGER WINDS WOULD LIKELY BE 
FOUND IN THE DEEP CONVECTION TO THE NORTH.
 
THE INITIAL MOTION ESTIMATE IS 305/12. THE CENTER WAS PLACED 
NORTHEAST OF ALL THE SATELLITE FIX POSITONS WHICH KEYED ON THE 
WELL-DEFINED MID-LEVEL CIRCULATION. HOWEVER...I HAVE FOLLOWED 
CONTINUITY WITH A CONSERVATIVE CLOUD FEATURE THAT WAS CLOSE TO THE 
LAST RECON FIX POSITION. BASED ON RECENT SATELLITE TRENDS...IT 
APPEARS THAT THE LOW-LEVEL AND MID-LEVEL CENTER...ALONG WITH THE 
BAND OF DEEP CONVECTION TO THE NORTH WILL MERGE AT A LOCATION ABOUT 
120 NMI NORTHWEST OF THE CURRENT POSITION IN ABOUT 12 HOURS OR SO. 
AT THAT TIME...GUSTAV WILL LIKELY TRANSITION OVER TO A FULL TROPICAL 
STORM. UNTIL THEN...THERE MAY SOME ERRATIC MOTION IN THE FORM OF 
LARGE LOOPS. HOWEVER...THE OVERALL TREND INDICATED BY THE NHC MODEL 
GUIDANCE CALLS FOR NORTHWEST MOTION THROUGH AT LEAST 18 HOURS. AFTER 
THAT...THE MODELS DIVERGE SIGNIFICANTLY...ESPECIALLY BY 36 HOURS. 
THE GFDN AND GFDL MODELS ARE THE FARTHEST WEST AND TAKE GUSTAV 
WEST-NORTHWESTWARD TO A POSITION ABOUT 30 TO 45 NMI SOUTH OF CAPE 
FEAR IN 36 HOURS AND KEEP IT STATIONARY UNTIL 48 HOURS...AND THEN 
MOVE IT RAPIDLY OFF TO THE NORTHEAST. HOWEVER...THE GLOBAL MODELS 
ARE IN BETTER AGREEMENT IN TAKING GUSTAV NORTHWEST FOR 24 HOURS OR 
SO AND THEN NORTHWARD TO JUST EAST OF CAPE HATTERAS AT 48 HOURS... 
AND THEN RAPIDLY RECURVES IT OFF TO THE NORTHEAST AFTER THAT AS A 
STRONG MID-LATITUDE TROUGH PICKS UP THE CYCLONE. THE OFFICIAL 
FORECAST IS A LITTLE TO THE LEFT OF THE PREVIOUS FORECAST AND CLOSE 
TO THE AVN-UKMET-NOGAPS CONSENSUS.
 
GIVEN THE UNCERTAINTY ON WHEN GUSTAV WILL MAKE THE TRANSITION OVER 
TO A FULL TROPICAL CYCLONE...THE INTENSITY FORECAST WAS HELD 
SLIGHTLY LOWER THAN THE SHIPS INTENSITY MODEL FORECAST...WHICH 
BRINGS THE CYCLONE UP TO 70 KT IN 36 HOURS. HOWEVER...BY 36 TO 48 
HOURS...GUSTAV IS EXPECTED TO BE MOVING ALONG THE WARM GULFSTREAM 
AND UNDER 10 TO 15 KT OF UPPER-LEVEL SHEAR. THIS MAY CREATE A BRIEF 
PERIOD OF IDEAL CONDITIONS THAT WILL ALLOW THE CYCLONE TO REACH 
HURRICANE STRENGTH.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     09/0300Z 31.2N  72.6W    40 KTS
12HR VT     09/1200Z 32.2N  74.1W    45 KTS
24HR VT     10/0000Z 33.0N  75.7W    55 KTS
36HR VT     10/1200Z 34.4N  76.0W    60 KTS
48HR VT     11/0000Z 35.7N  74.9W    65 KTS
72HR VT     12/0000Z 39.0N  66.0W    60 KTS...EXTRATROPICAL
 
 
NNNN