[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 152034
TCDAT1
TROPICAL STORM JEANNE DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT WED SEP 15 2004

JEANNE TRIED TO FORM AN EYE IN BOTH RADAR AND SATELLITE IMAGERY JUST
AS IT WAS MAKING LANDFALL IN SOUTHEASTERN PUERTO RICO.  WSR-88D
DATA FROM SAN JUAN INDICATES IT RETAINS A GOOD STRUCTURE ALTHOUGH
THE CURRENT DOPPLER WINDS DO NOT SUPPORT SUSTAINED SURFACE WINDS OF
HURRICANE FORCE.  THIS AGREES WITH AN AIR FORCE RESERVE HURRICANE
HUNTER AIRCRAFT...WHICH FOUND 57 KT FLIGHT-LEVEL WINDS AS IT FLEW
AROUND THE PUERTO RICO COAST.  THE INITIAL INTENSITY REMAINS 60 KT
FOR THIS ADVISORY.

THE INITIAL MOTION IS NOW 300/8.  THERE IS LITTLE CHANGE IN THE
TRACK FORECAST PHILOSOPHY.  JEANNE IS CURRENTLY ON THE SOUTHERN
PERIPHERY OF A DEEP LAYER RIDGE...AND MODEL GUIDANCE AGREES THAT
THIS RIDGE SHOULD PERSIST AND MOVE JEANNE ON A CONTINUED
WEST-NORTHWEST MOTION THROUGH ABOUT 48 HOURS.  BEYOND THAT
TIME...THE SOLUTIONS SOMEWHAT DIVERGE...OWING TO DIFFERENCES IN
HOW EACH MODEL HANDLES A WEAKENING IVAN OVER THE SOUTHEASTERN
UNITED STATES AND HOW MUCH RIDGING WILL REMAIN OVER THE EXTREME
WESTERN ATLANTIC.  MOST OF THE DYNAMICAL GUIDANCE CALLS FOR JEANNE
TO TURN NORTHWESTWARD AND EVEN NORTHWARD AFTER 48 HR.  WHILE THE
GFDL IS STILL A LEFT OUTLIER...IT HAS SHIFTED CONSIDERABLY TO THE
RIGHT IN BETTER AGREEMENT WITH THE OTHER MODELS.THE OFFICIAL
FORECAST IS SIMILAR TO THE PREVIOUS PACKAGE WITH A LITTLE MORE
NORTHWARD MOTION AFTER 72 HR.  THE FORECAST TRACK IS TO THE LEFT OF
ALL THE DYNAMICAL GUIDANCE SAVE THE GFDL AND FSU SUPERENSEMBLE.

THE INTENSITY FORECAST REMAINS A CHALLENGE.  WHILE THE OUTFLOW HAS
IMPROVED THIS AFTERNOON...AN UPPER-LEVEL TROUGH OR CYCLONIC SHEAR
AXIS IS CURRENTLY JUST WEST OF JEANNE.  LARGE-SCALE MODELS HAVE A
VARIETY OF IDEAS FOR THE EVOLUTION OF THIS FEATURE...FROM
PERSISTING FOR THREE OR MORE DAYS TO QUICK DISSIPATION.  MOST
LIKELY ENOUGH THIS FEATURE WILL CREATE ENOUGH SHEAR TO AT LEAST
SLOW INTENSIFICATION FOR 48-72 HR...AND THIS IS REFLECTED IN THE
INTENSITY FORECAST.  AFTER THAT...JEANNE SHOULD MOVE INTO A MORE
FAVORABLE ENVIRONMENT AND GRADUALLY STRENGTHEN.  ANOTHER
COMPLICATION IS LAND INTERACTION.  IF JEANNE MOVES OVER OR NEAR THE
DOMINICAN REPUBLIC ALL BETS WILL BE OFF ON THE INTENSITY FORECAST.

HURRICANE WARNINGS WILL REMAIN UP FOR PUERTO RICO AND THE VIRGIN
ISLANDS UNTIL JEANNE MOVES AWAY...AS EVEN SLIGHT STRENGTHENING AS
THE CENTER MOVES OFFSHORE COULD MAKE THE SYSTEM A HURRICANE.

FORECASTER BEVEN

FORECAST POSITIONS AND MAX WINDS

INITIAL      15/2100Z 18.4N  66.5W    60 KT...OVER PUERTO RICO
 12HR VT     16/0600Z 18.8N  67.7W    65 KT...OVER WATER
 24HR VT     16/1800Z 19.7N  69.2W    65 KT
 36HR VT     17/0600Z 20.6N  70.9W    65 KT
 48HR VT     17/1800Z 21.6N  72.4W    70 KT
 72HR VT     18/1800Z 23.5N  74.5W    75 KT
 96HR VT     19/1800Z 26.0N  76.5W    80 KT
120HR VT     20/1800Z 29.5N  77.5W    85 KT


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