[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 190237
TCDAT1
TROPICAL STORM JEANNE DISCUSSION NUMBER  22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT SAT SEP 18 2004

SATELLITE IMAGERY AND REPORTS FROM AN AIR FORCE RESERVE HURRICANE
HUNTER AIRCRAFT INDICATE THAT JEANNE IS POORLY ORGANIZED...POSSIBLY
DUE TO INTERACTION WITH AN UPPER-LEVEL LOW SEEN IN WATER VAPOR
IMAGERY JUST SOUTH OF THE STORM.  THE CIRCULATION IS ELONGATED FROM
THE NEW CENTER THAT FORMED THIS AFTERNOON TO THE OLD CENTER...WHICH
HAS MOVED EASTWARD AND IS NOW BETWEEN GREAT INAGUA ISLAND AND
HAITI.  THE STRONGEST CONVECTION IS CURRENTLY WELL-REMOVED TO THE
EAST OF THE CENTER.  THE AIRCRAFT FOUND A MINIMUM PRESSURE OF 1002
MB AND MAXIMUM FLIGHT-LEVEL WINDS OF 44 KT WELL TO THE NORTHEAST OF
THE NEW CENTER.  BASED ON THIS...THE MAXIMUM INTENSITY REMAINS 40
KT...ALTHOUGH THIS MAY BE GENEROUS.

THE INITIAL MOTION IS A HIGHLY UNCERTAIN 360/5.  IF JEANNE IS NOT
ACTUALLY YET MOVING NORTH...IT WILL BE SOON AS SATELLITE...
RAWINSONDE...AND SURFACE OBSERVATIONS SHOW A WEAK BUT DEEP-LAYER
TROUGH HAS DEVELOPED OVER FLORIDA IN ASSOCIATION WITH THE REMNANTS
OF IVAN.  THIS HAS ERODED THE RIDGE NORTH AND NORTHWEST OF JEANNE
AND SHOULD ALLOW A NORTHWARD MOTION.  LARGE-SCALE MODELS SUGGEST
THIS SHOULD CONTINUE FOR 48 HR OR SO...THEN POSSIBLY BECOME A
NORTH-NORTHEASTWARD MOTION.  THE FIRST 72 HR OF THE FORECAST TRACK
FOLLOWS THIS SCENARIO...BEING A LITTLE SLOWER THAN AND ALONG THE
LEFT SIDE OF THE ENVELOPE OF DYNAMICAL MODELS.  AFTER 72 HR...THE
LARGE-SCALE MODELS FORECAST A DEEP-LAYER RIDGE TO BUILD NORTH AND
NORTHWEST OF JEANNE IN THE WAKE OF A DEEP-LAYER TROUGH MOVING
THROUGH THE CANADIAN ATLANTIC PROVINCES.  THIS SHOULD BLOCK THE
NORTHWARD MOTION AND COULD TURN JEANNE BACK WESTWARD BY 120 HR.
DYNAMICAL GUIDANCE CALLS FOR LOOPS OF VARIOUS SIZES AND SPEEDS...
WITH 120 HR POSITIONS BETWEEN 67W AND 76W.  THE FORECAST TRACK FOR
72-120 HR WILL NOT CALL FOR A COMPLETE LOOP...BUT WILL SHOW A
HALF-LOOP THAT IS SMALLER AND SLOWER THAN THAT OF THE GUIDANCE.
OBVIOUSLY...THE 96 AND 120 HR FORECASTS HAVE A HIGHER THAN NORMAL
LEVEL OF UNCERTAINTY.

THE INTENSITY FORECAST ALSO HAS HIGH UNCERTAINTY.  IN THE SHORT
TERM...THE BROAD CIRCULATION AND THE LACK OF DEEP CONVECTION NEAR
THE CENTER WILL AT LEAST SLOW INTENSIFICATION.  UPPER-LEVEL WINDS
SHOULD BECOME MORE FAVORABLE FOR DEVELOPMENT IN ABOUT 24 HR...BUT
BY THAT TIME JEANNE MAY BE PASSING OVER THE SEA SURFACE TEMPERATURE
WAKE OF FRANCES...WHERE SST ANALYSES INDICATE TEMPERATURES BELOW
28C IN SOME AREAS.  THIS MAY COUNTER THE OTHERWISE FAVORABLE
ENVIRONMENT.  AFTER 48-72 HR...SHEAR IS FORECAST TO INCREASE AND
JEANNE MAY INTERACT WITH A COLD FRONT...BOTH OF WHICH WOULD LIMIT
STRENGTHENING.  THE SHIPS AND GFDL MODELS BOTH TAKE JEANNE TO 65-70
KT MAXIMUM WINDS IN 48-72 HR FOLLOWED BY LITTLE CHANGE IN
STRENGTH...AND THE INTENSITY FORECAST FOLLOWS THIS.

FORECASTER BEVEN

FORECAST POSITIONS AND MAX WINDS

INITIAL      19/0300Z 22.4N  72.3W    40 KT
 12HR VT     19/1200Z 23.4N  72.5W    40 KT
 24HR VT     20/0000Z 24.8N  72.5W    45 KT
 36HR VT     20/1200Z 26.3N  72.2W    50 KT
 48HR VT     21/0000Z 27.4N  71.8W    60 KT
 72HR VT     22/0000Z 28.0N  71.0W    65 KT
 96HR VT     23/0000Z 27.5N  70.5W    65 KT
120HR VT     24/0000Z 27.0N  71.0W    65 KT


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