[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT44 KNHC 072047
TCDAT4
HURRICANE IVAN DISCUSSION NUMBER  22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT TUE SEP 07 2004

AN AIR FORCE RECONNAISSANCE PLANE JUST MEASURED A PRESSURE OF 956 MB
WITH A DROP AND 955 MB EXTRAPOLATED FROM 700 MB. IT ALSO MEASURED
118 KNOTS AT FLIGHT LEVEL AND A CLOSED EYEWALL OF 14 NMI DIAMETER.
T-NUMBERS REMAIN AT 5.5 ON THE DVORAK SCALE. INITIAL INTENSITY IS
105 KNOTS. SHIPS MODEL INDICATE THAT THE SHEAR WILL REMAIN LOW OVER
THE CENTRAL AND WESTERN CARIBBEAN. GLOBAL MODELS APPEAR TO SHOW A
FAVORABLE UPPER-LEVEL ENVIRONMENT FOR STRENGTHENING. IN
ADDITION...IVAN IS EXPECTED TO REACH THE WESTERN CARIBBEAN SEA
WHERE THERE IS AN AREA OF HIGH OCEAN HEAT CONTENT...HIGH OCTANE GAS
FOR HURRICANES...WHICH COULD ADD TO THE INTENSIFICATION.  IVAN
COULD BECOME STRONGER THAN FORECAST. INDICATIONS ARE THAT THERE
WILL BE A VERY DANGEROUS HURRICANE OVER THE NORTHWESTERN CARIBBEAN
SEA...WESTERN CUBA OR SOUTHEASTERN GULF OF MEXICO IN FIVE DAYS.

THERE HAS BEEN NO CHANGE IN THE STEERING AND IVAN IS STILL MOVING
TOWARD THE WEST OR 280 DEGREES AT 16 KNOTS. THIS GENERAL MOTION IS
EXPECTED TO CONTINUE FOR THE NEXT 3 DAYS. THEREAFTER...THE FORECAST
BECOMES UNCERTAIN. GLOBAL MODELS CONTINUE TO DEVELOP A TROUGH OVER
THE CENTRAL UNITED STATES AND THE GULF OF MEXICO. THIS TROUGH IS
FORECAST TO ERODE THE RIDGE LEAVING A LARGE AREA OF WEAK STEERING
CURRENTS IN THE NORTHWESTERN CARIBBEAN AND SOUTHEASTERN GULF OF
MEXICO.  BY THEN...THE HURRICANE COULD MOVE NORTH OVER WESTERN CUBA
AND SOUTH FLORIDA AS INDICATED BY THE GFS...THE UK AND NOGAPS...OR
CONTINUE ON A SLOW WEST-NORTHWEST TRACK AS INDICATED BY THE GFDL
AND THE FSU SUPERENSEMBLE. THE LATTER ASSUMES THAT THE TROUGH IN
THE GULF OF MEXICO WILL NOT BE STRONG ENOUGH TO STEER THE HURRICANE
NORTHWARD...AND THAT THERE WILL BE ENOUGH RIDGING TO STEER THE
HURRICANE TOWARD WESTERN CUBA AND THE GULF OF MEXICO. THE OFFICIAL
FORECAST IS IN AGREEMENT WITH THE LATTER OPTION BIASED TOWARD THE
CONSENSUS.

FORECASTER AVILA

FORECAST POSITIONS AND MAX WINDS

INITIAL      07/2100Z 12.0N  62.0W   105 KT
 12HR VT     08/0600Z 12.5N  64.5W   115 KT
 24HR VT     08/1800Z 13.5N  67.7W   120 KT
 36HR VT     09/0600Z 14.7N  70.7W   120 KT
 48HR VT     09/1800Z 16.0N  73.5W   120 KT
 72HR VT     10/1800Z 18.0N  77.5W   120 KT
 96HR VT     11/1800Z 20.0N  81.0W   120 KT
120HR VT     12/1800Z 23.0N  84.0W   120 KT


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