[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 182034
TCDAT1
TROPICAL STORM JEANNE DISCUSSION NUMBER  21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT SAT SEP 18 2004

HIGH RESOLUTION SATELLITE IMAGES SHOW THAT THE LOW-LEVEL CENTER OF
JEANNE THAT WAS TRACKED SINCE IT MOVED AWAY FROM HISPANIOLA HAS RUN
WESTWARD AHEAD OF THE CONVECTION...AND IS DISSIPATING. SURFACE DATA
FROM THE BAHAMAS AND FROM A RECONNAISSANCE PLANE INDICATE THAT A
NEW CENTER HAS REFORMED UNDER THE CONVECTION WELL TO THE NORTHEAST
OF THE PREVIOUS LOCATION. THIS BY NO MEANS INDICATES A
NORTHEASTWARD MOTION OF THE CYCLONE. THE INITIAL INTENSITY IS
ESTIMATED AT 40 KNOTS BASED ON SURFACE OBSERVATIONS FROM GRAND
TURK. AN UPPER-LOW WHICH GLOBAL MODELS WERE FORECASTING TO MOVE
SOUTH AND WEAKEN...INSTEAD MOVED OVER THE CYCLONE AND AMPLYFIED...
DISRUPTING THE CLOUD PATTERN. THIS RESULTED IN WEAKENING. NOW THIS
NEW CENTER LOCATION IS UNDER A LITTLE MORE FAVORABLE ENVIRONMENT
AND GLOBAL MODELS INSIST ON THE DEVELOPMENT OF AN UPPER-LEVEL
ANTICYLONE OVER THE SYSTEM. THIS SUGGESTS STRENGTHENING AS
INDICATED IN THE OFFICIAL FORECAST AND GOES ALONG WITH BOTH SHIPS
AND THE GFDL MODELS.

THE TRACK FORECAST REASONING HAS NOT CHANGED. IT IS ONLY BEING
SHIFTED EASTWARD DUE TO THE REFORMATION. JEANNE IS FORECAST TO MOVE
TOWARD THE NORTH-NORTHWEST AND NORTH ABOUT 6 KNOTS FOR THE NEXT 3
DAYS. THEREAFTER...A RATHER STRONG HIGH IS EXPECTED TO REPLACE THE
TROUGH AND DEPENDING HOW FAR NORTH JEANNE MOVES...THE CYCLONE COULD
BE BLOCKED AND MOVE WESTWARD OR COULD TURN NORTHEASTWARD FOLLOWING
THE TROUGH. SINCE THERE IS MUCH UNCERTAINTY IN GLOBAL MODELS BEYOND
3 DAYS...THE BEST OPTION AT THIS TIME IS TO KEEP JEANNE NEARLY
STATIONARY BETWEEN BERMUDA AND THE BAHAMAS AT DAYS THREE THROUGH
FIVE. IN FACT...NOW ALL THE RELIABLE GLOBAL MODELS...THE GFS...THE
UKMET AND NOGAPS KEEP THE CYCLONE LOOPING WITHIN THIS REGION
THROUGH THE PERIOD OR LONGER.

FORECASTER AVILA

FORECAST POSITIONS AND MAX WINDS

INITIAL      18/2100Z 22.0N  72.3W    40 KT
 12HR VT     19/0600Z 22.9N  72.5W    40 KT
 24HR VT     19/1800Z 24.1N  72.6W    40 KT
 36HR VT     20/0600Z 25.7N  72.5W    50 KT
 48HR VT     20/1800Z 27.0N  72.5W    60 KT
 72HR VT     21/1800Z 28.5N  71.5W    65 KT
 96HR VT     22/1800Z 28.5N  71.5W    65 KT
120HR VT     23/1800Z 28.5N  71.5W    65 KT


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