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TROPICAL DEPRESSION NINE DISCUSSION NUMBER   5
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT THU SEP 12 2002
 
TROPICAL DEPRESSION NINE HAS CONTINUED TO BECOME BETTER 
ORGANIZED...AT LEAST IN THE LOW-LEVELS. SURFACE OBSERVATIONS AND 
SATELLITE MICROWAVE IMAGERY INDICATE THE DEPRESSION HAS A TIGHT 
INNER CORE WIND FIELD WHILE THE OUTER WIND FIELD HAS ALSO EXPANDED 
AND STRENGTHENED...MAINLY IN THE EASTERN SEMICIRCLE. A SMALL BURST 
OF DEEP CONVECTION HAS DEVELOPED JUST SOUTH OF THE WELL-DEFINED 
SURFACE CENTER AND BANDING HAS IMPROVED TO THE EAST. THE INITIAL 
INTENSITY OF 30 KT IS BASED ON 2 SHIPS LOCATED WITHIN 30 NMI 
SOUTHEAST AND SOUTHWEST OF CENTER THAT REPORTED 30 KT AND A PRESSURE 
OF 1003.6 MB. A RECON AIRCRAFT IS CURRENTLY INVESTIGATING THE 
SYSTEM.
 
THE DEPRESSION HAS ESSENTIALLY BEEN STATIONARY THE PAST 3 HOURS 
AFTER LOOPING TO THE SOUTH AT AROUND 6 KT. HOWEVER...A GENERAL SLOW 
DRIFT TO THE NORTH IS EXPECTED TO RESUME LATER TONIGHT WITH A 
GRADUAL INCREASE IN FORWARD SPEED. THERE HAS BEEN A MAJOR WESTWARD 
SHIFT BY ALL OF THE MODEL GUIDANCE FOR THIS ADVISORY PACKAGE...WITH 
THE GFDL AND GFDN MODELS BEING THE FARTHEST WEST OVER THE SOUTHEAST 
TIP OF LOUISIANA IN ABOUT 24 HOURS. HOWEVER...INFORMATION FROM A 
GULFSTREAM-IV AIRCRAFT OVERFLYING THE CYCLONE INDICATES THAT WHILE 
THE MID- AND UPPER-LEVEL SHEAR HAS WEAKENED...THE FLOW WAS STILL 
FROM THE WEST ON THE WEST SIDE. 00Z UPPER-AIR DATA SHOWS THAT 500 MB 
HEIGHTS HAVE RISEN ABOUT 30 TO 40 METERS ACROSS FLORIDA AND CUBA 
DURING THE PAST 24 HOURS...WHICH INDICATES THAT THE SUBTROPICAL 
RIDGE IS BUILDING TO THE SOUTH OF THE DEPRESSION. THE INCREASED 
MID-LEVEL RIDGING TO THE EAST AND SOUTH SHOULD GRADUALLY BEGIN TO 
NUDGE THE CYCLONE NORTHWARD. WHILE THE NHC MODEL SUITE HAS SHIFTED 
WESTWARD...IT IS MORE TIGHTLY PACKED THAN ON PREVIOUS ADVISORIES. 
THE GFDL AND GFDN KEEP THE DEPRESSION SHALLOW AND WEAK...WHICH 
PROBABLY EXPLAINS THE MORE WESTWARD TRACK AS THE CYCLONE GETS 
STEERED MORE BY THE LOW-LEVEL EASTERLY FLOW. HOWEVER...THE OFFICIAL 
FORECAST CALLS FOR A STRONGER AND DEEPER SYSTEM TO BE STEERED MORE 
NORTHWARD BY THE BUILDING RIDGE TO THE EAST THROUGH 24 HOURS AND 
THEN TURN TOWARD THE NORTHEAST AFTER THAT AS AN APPROACHING 
UPPER-LEVEL TROUGH PICKS UP THE CYCLONE. ALSO...WITH SOME WESTWARD 
UPPER-LEVEL FLOW COMPONENT IMPINGING ON THE CYCLONE THROUGHOUT THE 
PERIOD...A MORE EASTWARD BIAS IS EXPECTED. THE OFFICIAL FORECAST 
TRACK IS A LITTLE WEST OF THE PREVIOUS TRACK AND IS BETWEEN THE AVN 
AND UKMET SOLUTIONS. IMPORTANT NOTE...A MORE WESTWARD TRACK THAN 
WHAT IS CURRENTLY FORECAST WOULD REQUIRE THE ISSUANCE OF TROPICAL 
STORM WARNINGS FOR SOUTHEAST LOUISIANA AND THE REMAINDER OF THE 
MISSISSIPPI GULF COAST BY FRIDAY MORNING.
 
WHILE THE UPPER-LEVEL SHEAR HAS WEAKENED AND IS FORECAST TO WEAKEN 
EVEN MORE PRIOR TO LANDFALL...THE PRESENCE OF DRY AIR TO THE WEST OF 
THE CYCLONE SHOULD HINDER THE DEVELOPMENT PROCESS. HOWEVER...BY 24 
TO 36 HOURS...THE AVN MODEL IS FORECASTING A WEAK RIDGE TO DEVELOP 
ABOVE THE CYCLONE WHICH MAY ALLOW FOR A BRIEF PERIOD OF MORE 
SIGNIFICANT STRENGTHENING TO OCCUR. THE SHIPS INTENSITY MODEL WAS 
CLOSELY FOLLOWED AND IT BRINGS THE SYSTEM TO 45 KT IN 36 HOURS.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     13/0300Z 26.6N  87.9W    30 KTS
12HR VT     13/1200Z 27.5N  88.0W    35 KTS
24HR VT     14/0000Z 29.0N  88.0W    45 KTS
36HR VT     14/1200Z 30.9N  86.9W    50 KTS...INLAND
48HR VT     15/0000Z 32.8N  84.8W    30 KTS...REMNANT LOW INLAND
72HR VT     16/0000Z 35.5N  79.5W    25 KTS...INLAND LOW
 
 
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