[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT44 KNHC 070305
TCDAT4
HURRICANE IVAN DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT MON SEP 06 2004

AN EVALUATION OF THE DATA FROM THE HURRICANE HUNTERS SUGGESTS THAT
IVAN HAS MAINTAINED ITS INTENSITY OVER THE LAST FEW HOURS.
DROPSONDES THROUGHOUT THE MISSION HAVE SHOWN A MODEST DROP IN
PRESSURE FROM 969 MB TO 963 MB.  THE MAXIMUM FLIGHT LEVEL WIND
MEASURED WAS 106 KT...CORRESPONDING TO A SURFACE WIND OF 85 KT.
SATELLITE INTENSITY ESTIMATES RANGE FROM 65 KT TO 90 KT...THE
INITIAL INTENSITY IS KEPT AT 90 KT.

THE INITIAL MOTION IS 275/18.  RECONNAISSANCE AIRCRAFT PROVIDED A
FIX TO THE SOUTH OF THE PREVIOUS FORECAST TRACK.  IVAN IS EXPECTED
TO RESUME A WEST-NORTHWEST COURSE SOON...AS UNIVERSALLY SUGGESTED
BY THE MODEL GUIDANCE.  DUE IN PART TO A MORE SOUTHERLY INITIAL
POSITION...THE FORECAST TRACK IS TO THE LEFT OF THE PREVIOUS ONE.
THERE IS A DIFFERENCE OF OPINION IN THE DYNAMICAL MODELS AT 96 AND
120 HOURS.  THE GFS...UKMET...AND THE FSU SUPERENSEMBLE BRING IVAN
WELL SOUTH OF CUBA TOWARD THE YUCATAN PENNINSULA.  NOGAPS AND THE
GFDL BRING IVAN MUCH CLOSER TO THE SOUTHERN COAST OF CUBA.  THE
OFFICIAL FORECAST SPLITS THE DIFFERENCE AND IS LINE WITH THE
CLOSELY PACKED MODEL CONSENSUS POINTS.

A NOAA JET IN IVAN THIS EVENING HAS FOUND THE EXISTENCE OF A SAHARAN
AIR LAYER IN THE NORTHERN QUADRANTS OF THE STORM.  THIS MAY HELP
EXPLAIN THE WEAKENING OF IVAN THROUGHOUT THE DAY TODAY.  IVAN IS
EXPECTED TO GRADUALLY INTENSIFY AS IT PROCEEDS TO THE WEST
THROUGHOUT THE FORECAST PERIOD.  SINCE THE NEW FORECAST KEEPS IVAN
AWAY FROM ANY MAJOR LAND AREAS...THE INTENSITY OF IVAN IN THE LATER
PERIODS ARE MAINTAINED.

FORECASTER LAWRENCE/HENNON

FORECAST POSITIONS AND MAX WINDS

INITIAL      07/0300Z 11.2N  57.2W    90 KT
 12HR VT     07/1200Z 11.8N  59.8W    95 KT
 24HR VT     08/0000Z 12.7N  62.9W   100 KT
 36HR VT     08/1200Z 13.7N  66.1W   105 KT
 48HR VT     09/0000Z 14.7N  69.1W   110 KT
 72HR VT     10/0000Z 17.2N  74.3W   115 KT
 96HR VT     11/0000Z 19.5N  78.7W   115 KT
120HR VT     12/0000Z 21.5N  82.4W   115 KT


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