[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT44 KNHC 030840
TCDAT4
TROPICAL STORM IVAN DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT FRI SEP 03 2004

SATELLITE INTENSITY ESTIMATES AT 06Z WERE 2.5...OR 35 KT...FROM BOTH
TAFB AND SAB.  BASED ON THIS AND THE IMPRESSIVE SATELLITE
SIGNATURE...T.D. NINE IS UPGRADED TO TROPICAL STORM IVAN.  IVAN
CONTINUES TO MOVE ON THE SOUTH SIDE OF A SUBTROPICAL RIDGE AND
THE INITIAL MOTION IS 275/12.  GLOBALS MODELS INDICATE THAT THE
SUBTROPICAL RIDGE WILL MOVE WESTWARD IN TANDEM WITH IVAN THROUGH
THE FORECAST PERIOD. ACCORDINGLY...DYNAMICAL MODELS ARE IN
EXCELLENT AGREEMENT...SAVE NOGAPS WHICH IS SLOWER AND MORE
POLEWARD...AND THERE ARE NO MAJOR CHANGES TO THE OFFICIAL TRACK.
THE OFFICIAL FORECAST IS VERY CLOSE TO THE MODEL CONSENSUS AND
ESSENTIALLY MAINTAINS A CONSISTENT FORWARD SPEED OF 15 TO 17 KNOTS.

IVAN IS UNDER THE INFLUENCE OF SOME EASTERLY SHEAR AND THE LOW
LEVEL CIRCULATION IS SITUATED ON THE EASTERN SIDE OF THE DEEP
CONVECTION.  HOWEVER...THE SHEAR IS FORECAST TO WEAKEN SLIGHTLY AND
IVAN WILL BE MOVING OVER VERY WARM WATERS. THE GFDL CONTINUES TO
AGGRESSIVELY STRENGTHEN IVAN TO A CATEGORY FOUR HURRICANE BY 84
HOURS BUT THIS APPEARS A BIT MUCH GIVEN THE EASTERLY SHEAR WILL NOT
TOTALLY DIMINISH. THE OFFICIAL FORECAST CALLS FOR A MORE MODEST
STRENGTHENING IN LINE WITH THE SHIPS AND FSU SUPER ENSEMBLE.

FORECASTER RHOME/JARVINEN


FORECAST POSITIONS AND MAX WINDS

INITIAL      03/0900Z 10.0N  30.7W    35 KT
 12HR VT     03/1800Z 10.1N  33.0W    40 KT
 24HR VT     04/0600Z 10.3N  36.3W    50 KT
 36HR VT     04/1800Z 10.6N  39.5W    55 KT
 48HR VT     05/0600Z 10.9N  42.7W    60 KT
 72HR VT     06/0600Z 11.6N  49.0W    70 KT
 96HR VT     07/0600Z 13.0N  55.2W    80 KT
120HR VT     08/0600Z 15.0N  61.0W    85 KT


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