[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 142052
TCDAT1
TROPICAL STORM JEANNE DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT TUE SEP 14 2004

RECONNAISSANCE...SATELLITE...AND SAN JUAN DOPPLER RADAR DATA
INDICATE THAT TROPICAL STORM JEANNE HAS CONTINUED TO STRENGTHEN.
THE PRESSURE HAS DECREASED TO 998 MB...DOWN 4 MB IN 2 HOURS. THE
INITIAL INTENSITY OF 50 KT IS BASED ON A 1000-FT FLIGHT-LEVEL WIND
OF 58 KT...EQUAL TO ABOUT A 46-KT SURFACE WIND...AND THE IMPROVED
APPEARANCE IN SATELLITE AND RADAR IMAGERY SINCE THE RECON FIX.

THE INITIAL MOTION ESTIMATE IS 290/08...ALTHOUGH THE TWO RECON FIX
POSITIONS SUGGEST THE MOTION COULD BE CLOSER TO 285 DEGREES. THE
18Z 500 MB HEIGHT AT SAN JUAN HAS NOT CHANGED IN THE LAST 24 HOURS
...SUGGESTING THAT THE LARGE SUBTROPICAL RIDGE TO THE NORTH IS
HOLDING STEADY. ALL OF THE NHC MODEL GUIDANCE...EXCEPT FOR THE BAM
MODELS AND NOGAPS...MOVE JEANNE IMMEDIATELY NORTHWESTWARD AND TAKE
THE CYCLONE JUST NORTH OF PUERTO RICO. THIS SEEMS UNREALISTIC GIVEN
THE PAST 18-HR MOTION OF JEANNE AND THE 18Z SAN JUAN UPPER-AIR
DATA. SO IN THE SHORT TERM...JEANNE IS FORECAST TO PASS NEAR THE
SOUTH COAST OF PUERTO RICO IN 18-24 HOURS...AND THEN SKIRT THE
NORTH COAST OF THE DOMINICAN REPUBLIC AFTER THAT THROUGH 48 HOURS.
WHILE THE SPECIFIC SYNOPTIC DETAILS OF THE VARIOUS MODELS DIFFER
SIGNIFICANTLY...THERE IS GENERAL AGREEMENT THAT THE RIDGE CURRENTLY
LOCATED NORTH OF JEANNE WILL REMAIN INTACT THROUGHOUT THE FORECAST
PERIOD. HOWEVER...THE GFS AND GFDL MODELS WEAKEN THE RIDGE ENOUGH
TO ALLOW JEANNE TO MOVE ALMOST DUE NORTH AFTER 72 HOURS ALONG 70W
LONGITUDE. GIVEN THE GFS RECENT POOR HISTORY OF FORECASTING TOO
WEAK OF A RIDGE OVER THE WESTERN ATLANTIC...THE OFFICIAL FORECAST
TRACK LEANS MORE TOWARD THE UKMET AND NOGAPS MODELS. IT SHOULD BE
POINTED OUT THAT THE CANADIAN AND ECMWF MODELS KEEP A STRONG RIDGE
BETWEEN JEANNE AND IVAN THROUGH 120 HOURS...AND TAKE THE CYCLONE
WESTWARD TOWARD THE BAHAMAS AND THE FLORIDA PENINSULA.

JEANNE HAS DEVELOPED AN EXCELLENT OUTFLOW PATTERN AND THIS IS
EXPECTED TO PERSIST UNTIL THE CYCLONE NEARS PUERTO RICO. THIS
OUTFLOW PATTERN...COMBINED WITH NEARLY 29C SSTS AND A VERY TIGHT
INNER-CORE WIND FIELD AS NOTED IN THE RECON DATA...SHOULD ALLOW
JEANNE TO POSSIBLY REACH HURRICANE STRENGTH BEFORE IT REACHES
PUERTO RICO. AFTER THAT...CLOSE PROXIMITY TO HISPANIOLA SHOULD
INHIBIT STRENGTHENING UNTIL AFTER 72 HOURS...WHEN JEANNE IS
FORECAST TO MOVE AWAY FROM HISPANIOLA...AND NORTHERLY VERTICAL
SHEAR IS EXPECTED TO WEAKEN AND BECOME EASTERLY IN DIRECTION.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      14/2100Z 16.8N  63.9W    50 KT
 12HR VT     15/0600Z 17.4N  65.3W    55 KT
 24HR VT     15/1800Z 18.1N  67.0W    65 KT...INLAND PUERTO RICO
 36HR VT     16/0600Z 18.9N  68.6W    65 KT...NEAR DOM. REPUBLIC
 48HR VT     16/1800Z 19.7N  70.0W    65 KT...NEAR DOM. REPUBLIC
 72HR VT     17/1800Z 20.9N  72.0W    65 KT
 96HR VT     18/1800Z 22.5N  74.5W    70 KT
120HR VT     19/1800Z 24.5N  75.5W    75 KT


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