[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 190839
TCDAT1
TROPICAL STORM JEANNE DISCUSSION NUMBER  23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT SUN SEP 19 2004

AN AIR FORCE HURRICANE HUNTER AIRCRAFT HAS BEEN INVESTIGATING JEANNE
AND THEY FOUND PEAK FLIGHT LEVEL...1500 FT...OF 53 KT ABOUT 50 N MI
NORTHEAST OF THE CENTER.  USING A STANDARD REDUCTION FOR THIS
ALTITUDE GIVES A MAXIMUM SURFACE WIND SPEED OF 40-45 KT.  THE
TROPICAL CYCLONE HAS BEEN MOVING AWAY FROM THE DISRUPTING INFLUENCE
OF AN UPPER-LEVEL LOW...AND CURRENTLY SEEMS TO BE ESTABLISHING A
BETTER-DEFINED UPPER-LEVEL OUTFLOW PATTERN.  THEREFORE SOME
STRENGTHENING IS LIKELY OVER THE NEXT COUPLE OF DAYS.  THE OFFICIAL
FORECAST SHOWS JEANNE EVENTUALLY RESTRENGTHENING INTO A
HURRICANE... AS DO THE SHIPS AND GFDL MODELS.  HOWEVER...THE GFS
200 MB WIND FOREAST SHOWS FAIRLY STRONG WESTERLY FLOW...IMPLYING
SIGNIFICANT SHEAR...OVER THE AREA WHERE THE TROPICAL CYCLONE IS
FORECAST TO BE LOCATED IN 72 HOURS.  JEANNE MAY HAVE TO OVERCOME A
RATHER HOSTILE UPPER-LEVEL ENVIRONMENT ON ITS WAY TO REGAINING
HURRICANE STATUS.

BASED ON THE RECON FIXES...THE INITIAL MOTION ESTIMATE IS 340/6.  A
MID-LEVEL TROUGH OVER THE FLORIDA PENINSUAL IS FORECAST TO MOVE
EASTWARD AND TURN JEANNE NORTHWARD AND NORTH-NORTHEASTWARD DURING
THE NEXT 24-36 HOURS.  HOWEVER...IN 2-3 DAYS...THIS TROUGH IS
LIKELY TO BYPASS THE TROPICAL CYCLONE AS AN UNUSUALLY STRONG
DEEP-LAYER HIGH BUILDS OVER THE EASTERN UNITED STATES.  A RIDGE
EXTENDING FROM THIS HIGH IS PREDICTED...BY THE DYNAMICAL MODELS...
TO BLOCK THE NORTHEASTWARD MOTION OF JEANNE...AND CAUSE THE
TROPICAL CYCLONE TO EXECUTE A CLOCKWISE LOOP.  THIS OFFICIAL
FORECAST SHOWS A LITTLE WIDER LOOP THAN THE PREVIOUS ADVISORY...BUT
HAS THE SAME GENERAL IDEA.  IT SHOULD BE REPEATED THAT THIS IS A
LOWER THAN NORMAL CONFIDENCE FORECAST.

SINCE JEANNE IS MOVING AWAY FROM THE SOUTHEASTERN BAHAMAS AND HAS
TROPICAL STORM FORCE WINDS CONFINED TO THE NORTHEAST AND SOUTHEAST
QUADRANTS...THE GOVERNMENT OF THE BAHAMAS INTENDS TO DISCONTINUE
WATCHES AND WARNINGS FOR THE BAHAMAS SHORTLY.

FORECASTER PASCH

FORECAST POSITIONS AND MAX WINDS

INITIAL      19/0900Z 23.2N  72.5W    40 KT
 12HR VT     19/1800Z 24.1N  72.6W    45 KT
 24HR VT     20/0600Z 25.5N  72.2W    50 KT
 36HR VT     20/1800Z 27.0N  71.7W    55 KT
 48HR VT     21/0600Z 28.0N  70.5W    60 KT
 72HR VT     22/0600Z 27.0N  70.0W    65 KT
 96HR VT     23/0600Z 26.0N  70.0W    65 KT
120HR VT     24/0600Z 26.0N  71.5W    65 KT

$$
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