wxman007
(Meteorologist)
Fri Sep 13 2002 03:18 AM
Wow...

Awesome discussion...Kudos Mr Stewart...probably the best of the season!

028
WTNT44 KNHC 130304
TCDAT4
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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