[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 151437
TCDAT1
TROPICAL STORM JEANNE DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT WED SEP 15 2004

SATELLITE IMAGERY AND WSR-88D RADAR DATA FROM SAN JUAN SUGGEST THAT
JEANNE MAY BE SUFFERING FROM SHEAR AND DRY AIR INTRUSION THIS
MORNING.  THE LOW LEVEL CENTER IS AT THE SOUTHERN EDGE OF THE
PRIMARY CONVECTION...AND THE OUTER BANDING HAS BECOME SOMEWHAT
RAGGED COMPARED TO YESTERDAY.  SATELLITE INTENSITY ESTIMATES ARE 65
KT FROM TAFB AND SAB...AND 45 KT FROM AFWA.  DOPPLER RADAR WINDS
SUGGESTS SURFACE WINDS OF ABOUT 55-60 KT.  BASED ON ALL THE ABOVE...
THE INITIAL INTENSITY WILL BE 60 KT.

THE INITIAL MOTION REMAINS 295/7.  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.  ON THE OTHER
HAND...THE GFDL IS A LEFT OUTLIER...CALLING FOR JEANNE TO TRACK
ACROSS THE DOMINICAN REPUBLIC AND THE BAHAMAS TO SOUTH FLORIDA BY
DAY 5.  THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS PACKAGE
WITH A LITTLE MORE NORTHWARD MOTION AFTER 96 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.  AN UPPER-LEVEL TROUGH
OR CYCLONIC SHEAR AXIS IS CURRENTLY JUST WEST OF JEANNE AND CAUSING
SHEAR.  LARGE-SCALE MODELS HAVE A VARIETY OF IDEAS FOR THE
EVOLUTION OF THIS FEATURE...FROM PERSISTING FOR THREE OR MORE DAYS
TO ALMOST INSTANT 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.
PASSAGE OVER PUERTO RICO MAY AT LEAST SLOW DEVELOPMENT...AND IF
JEANNE MOVES OVER OR NEAR THE DOMINICAN REPUBLIC ALL BETS ARE OFF
ON THE INTENSITY FORECAST.

IT SHOULD BE NOTED THAT JEANNE COULD STILL BECOME A HURRICANE BEFORE
REACHING PUERTO RICO.  EVEN IF IT DOES NOT...HURRICANE FORCE WINDS
ALOFT SEEN ON THE SAN JUAN RADAR WILL AFFECT HIGHER ELEVATIONS.

FORECASTER BEVEN

FORECAST POSITIONS AND MAX WINDS

INITIAL      15/1500Z 17.8N  65.8W    60 KT
 12HR VT     16/0000Z 18.3N  66.9W    65 KT
 24HR VT     16/1200Z 19.2N  68.6W    65 KT
 36HR VT     17/0000Z 20.2N  70.4W    65 KT
 48HR VT     17/1200Z 21.1N  71.9W    65 KT
 72HR VT     18/1200Z 23.0N  74.5W    70 KT
 96HR VT     19/1200Z 25.5N  76.5W    75 KT
120HR VT     20/1200Z 28.0N  77.5W    80 KT


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