[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 140839
TCDAT4
HURRICANE IVAN DISCUSSION NUMBER  48
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT TUE SEP 14 2004

A RECONNAISSANCE PLANE JUST WENT THROUGH THE EYE OF IVAN AND
MEASURED A PRESSURE OF 924 MB WITH A DROP AND ESTIMATED 920 MB BY
EXTRAPOLATION. MAX FLIGHT LEVEL WINDS SO FAR ARE 142 KNOTS AND WITH
THE PRESSURE RISING...THE INITIAL INTENSITY MAY BE LITTLE LOWER.
BECAUSE THE PLANE HAS NOT SAMPLED THE ENTIRE CIRCULATION YET...WE
WILL KEEP THE WINDS AT 140 KNOTS AT THIS TIME. SATELLITE IMAGES
CONTINUE TO SHOW A WELL-DEFINED EYE SURROUNDED BY VERY COLD
CONVECTIVE TOPS. SOME WEAKENING IS FORECAST AS IVAN MOVES FARTHER
NORTH OVER THE EASTERN GULF OF MEXICO DURING THE NEXT COUPLE OF
DAYS...AND ENCOUNTERS SOME WESTERLY SHEAR. HOWEVER...IVAN SHOULD
STILL BE A MAJOR HURRICANE WHEN IT REACHES THE UNITED STATES COAST.

IVAN IS MOVING TOWARD THE NORTHWEST OR 320 DEGREES AT 8 KNOTS. THERE
HAS BEEN NO SIGNIFICANT CHANGE IN THE STEERING WHICH CONTINUES TO
BE CONTROLLED BY A SUBTROPICAL RIDGE CENTERED OVER THE WESTERN
ATLANTIC. IVAN IS FORECAST TO GRADUALLY TURN NORTHWARD AROUND THE
PERIPHERY OF THE SUBTROPICAL RIDGE WITH NO SIGNIFICANT CHANGE IN
SPEED BEFORE LANDFALL. THIS IS CONSISTENT WITH GUIDANCE WHICH
BRINGS THE HURRICANE NEAR THE NORTH CENTRAL GULF COAST IN ABOUT 48
HOURS. ONCE INLAND...THE GUIDANCE SLOWS DOWN A WEAKENED IVAN OVER
THE SOUTHEASTERN UNITED STATES. THIS COULD PRODUCE ANOTHER
SIGNIFICANT RAIN EVENT IN THAT AREA.

NOTE: DUE TO FORECAST ERRORS...ONE SHOULD NOT FOCUS ON THE EXACT
TRACK AS THE EVENTUAL LANDFALL POINT. THE ENTIRE HURRICANE WATCH
AREA IS AT RISK.

FORECASTER AVILA

FORECAST POSITIONS AND MAX WINDS

INITIAL      14/0900Z 22.6N  86.0W   140 KT
 12HR VT     14/1800Z 24.0N  86.6W   140 KT
 24HR VT     15/0600Z 26.0N  87.7W   135 KT
 36HR VT     15/1800Z 28.0N  88.3W   130 KT
 48HR VT     16/0600Z 30.0N  88.0W   120 KT
 72HR VT     17/0600Z 33.5N  86.5W    50 KT...INLAND
 96HR VT     18/0600Z 35.5N  84.5W    20 KT...INLAND
120HR VT     19/0600Z 37.0N  82.0W    20 KT...INLAND


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