[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT44 KNHC 052035
TCDAT4
HURRICANE IVAN DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT SUN SEP 05 2004

LATEST SATELLITE IMAGERY INDICATES THAT IVAN HAS INTENSIFIED AND
MAXIMUM WINDS ARE ESTIMATED TO BE NEAR 110 KT.  AS NOTED
EARLIER...IT IS UNPRECEDENTED TO HAVE A HURRICANE THIS STRONG AT
SUCH A LOW LATITUDE IN THE ATLANTIC BASIN.  THE EYE IS EMBEDDED IN
CLOUD TOPS COLDER THAN -70 DEG C AND THE UPPER-LEVEL OUTFLOW IS
QUITE SYMMETRIC AND STRONG.  THE OFFICIAL WIND SPEED FORECAST IS
CONSERVATIVE BECAUSE OF OUR LIMITED SKILL IN PREDICTING INTENSITY
CHANGE...AND OBVIOUSLY IVAN COULD BECOME STRONGER THAN INDICATED
HERE.

INITIAL MOTION IS WNW...285/18.  A STRONG DEEP-LAYER HIGH IS LIKELY
TO BE MAINTAINED TO THE NORTH OF THE HURRICANE...AND THIS PATTERN
SHOULD MAINTAIN ABOUT THE SAME STEERING FLOW FOR IVAN OVER THE NEXT
FEW DAYS.  LATE IN THE PERIOD...GLOBAL MODELS FORECASTS AT THE 500
MB LEVEL ARE SHOWING A TROUGH OVER THE EAST-CENTRAL UNITED STATES
AND AN ANTICYCLONE OVER THE WESTERN ATLANTIC WITH A RIDGE EXTENDING
TO FLORIDA.  HOWEVER THE DETAILS VARY FROM MODEL TO MODEL...AND
THERE IS UNCERTAINTY IN HOW MUCH IVAN WILL TURN TOWARD THE
NORTHWEST BY DAY 5.  THE OFFICIAL FORECAST IS CLOSE TO A CONSENSUS
OF THE DYNAMICAL MODELS WHICH EXCLUDES THE GFS.  THE LATTER MODEL
IS INITIALIZING THIS TROPICAL CYCLONE TOO WEAK AND SHALLOW...SO ITS
MORE SOUTHERN TRACK IS CONSIDERED UNREALISTIC.

FORECASTER PASCH

FORECAST POSITIONS AND MAX WINDS

INITIAL      05/2100Z 10.4N  47.7W   110 KT
 12HR VT     06/0600Z 11.0N  50.4W   115 KT
 24HR VT     06/1800Z 11.9N  54.0W   120 KT
 36HR VT     07/0600Z 12.8N  57.5W   125 KT
 48HR VT     07/1800Z 13.6N  61.0W   125 KT
 72HR VT     08/1800Z 15.5N  66.5W   125 KT
 96HR VT     09/1800Z 18.5N  71.5W    70 KT...INLAND
120HR VT     10/1800Z 21.5N  76.0W    75 KT...OVER WATER

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