[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT44 KNHC 091452
TCDAT4
HURRICANE IVAN DISCUSSION NUMBER  29
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT THU SEP 09 2004

THE LAST RECONNAISSANCE FIX WAS EARLIER THIS MORNING ABOUT 1141Z.
FLIGHT LEVEL...700 MB...WINDS WERE 156 KNOTS WITH AN EXTRAPOLATED
PRESSURE OF 917 MB AND 921 MB MEASURED BY A DROP. IVAN HAS AN
OUTSTANDING SATELLITE PRESENTATION...HOWEVER...THE RING OF
CONVECTION SURROUNDING THE EYE HAS WEAKENED A LITTLE BIT. INITIAL
INTENSITY REMAINS AT 140 KNOTS. HURRICANES NORMALLY DO NOT MAINTAIN
SUCH PEAK INTENSITY FOR A LONG TIME AND MOST LIKELY THERE WILL WE
SOME SLIGHT WEAKENING. THE HURRICANE WILL PROBABLY FLUCTUATE
BETWEEN CAT 4 AND 5 UNTIL IT REACHES CUBA.  THEREAFTER..THE EFFECTS
OF LAND...INCREASING SHEAR AND LOWER OCEAN HEAT CONTENT WILL CAUSE
WEAKENING.

IVAN IS MOVING TOWARD THE WEST-NORTHWEST AT 13 KNOTS. THIS GENERAL
MOTION WITH A GRADUAL DECREASE IN FORWARD SPEED IS EXPECTED DURING
THE NEXT 3 DAYS. THERE HIGH CONFIDENCE IN THIS PORTION OF THE
FORECAST BECAUSE THE HURRICANE WILL BE STEERED BY THE FLOW
SURROUNDING A WELL-ESTABLISHED SUBTROPICAL RIDGE. ALL MODELS ARE
HIGHLY CLUSTERED DURING THIS PERIOD...BRINGING THE HURRICANE
BETWEEN CUBA AND THE CAYMAN ISLANDS. THEREAFTER...THE FORECAST
TRACK BECOMES HIGHLY UNCERTAIN. STEERING CURRENTS ARE FORECAST TO
COLLAPSE AND CONSEQUENTLY...THE HURRICANE IS EXPECTED TO SLOW DOWN
AS IT CROSSES CUBA.  A RIDGE OVER THE BAHAMAS A LITTLE STRONGER
THAN ANTICIPATED...WILL BRING THE HURRICANE TOWARD THE EASTERN GULF
OF MEXICO AS INDICATED BY THE UK...CANADIAN AND NOGAPS GLOBAL
MODELS. A WEAKER RIDGE THAN ANTICIPATED COULD RESULT ON A MORE
NORTHWARD TRACK OVER THE BAHAMAS AND NEARBY THE EAST COAST OF
FLORIDA AS INDICATED BY THE GFS. THE 4-5 DAY OFFICIAL
FORECAST...WHICH IS HIGHLY UNCERTAIN...CALLS FOR A SOLUTION IN
BETWEEN...BRINGING THE HURRICANE OVER WEST/CENTRAL CUBA INTO THE
SOUTHEASTERN GULF OF MEXICO AND THEN FLORIDA.

FORECASTER AVILA

FORECAST POSITIONS AND MAX WINDS

INITIAL      09/1500Z 14.5N  71.4W   140 KT
 12HR VT     10/0000Z 15.3N  73.3W   140 KT
 24HR VT     10/1200Z 17.0N  75.2W   135 KT
 36HR VT     11/0000Z 18.5N  77.3W   135 KT
 48HR VT     11/1200Z 19.5N  79.0W   135 KT
 72HR VT     12/1200Z 21.0N  80.5W   130 KT
 96HR VT     13/1200Z 24.0N  82.0W   115 KT
120HR VT     14/1200Z 28.5N  82.0W    85 KT INLAND


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