HOME	ACTIVE CYCLONES	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

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TROPICAL STORM FERNANDA DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT WED AUG 18 1999
 
THE TROPICAL CYCLONE REMAINS IN A SHEARED STATE WITH MULTI-CHANNEL
SATELLITE IMAGERY INDICATING THAT THE CIRCULATION CENTER IS JUST
ON THE NORTHEAST EDGE OF THE DEEP CONVECTION.  THIS IS CONFIRMED
BY 85GHZ DATA FROM THE LATEST TRMM SATELLITE PASS.  DVORAK CURRENT
INTENSITY ESTIMATES FROM TAFB...SAB AND AFGW ARE ALL 35 KT.
THEREFORE...TROPICAL DEPRESSION TEN-E IS UPGRADED TO TROPICAL STORM
FERNANDA.
 
USING THE TRMM POSITION ESTIMATE AND THE LATEST SATELLITE FIXES THE
INITIAL MOTION ESTIMATE IS NOW 295/15 KT.  THIS REPRESENTS A 4 KT
INCREASE IN FORWARD SPEED FROM THE LAST ADVISORY. SOME OF THE
DYNAMIC-BASED GUIDANCE IS STILL DIVERSE WITH NOGAPS BRINGING THE
CYCLONE NORTH AND DISSIPATING IT BY 36 HRS WHILE THE UKMET MOVES THE
SYSTEM WEST-NORTHWEST THROUGH 24 HRS BEFORE MAKING A SHARP LEFT TURN
TOWARD THE SOUTH-SOUTHEAST. IN BOTH INSTANCES EACH MODEL FAVORS THE
DEVELOPMENT OF A SYSTEM NEAR THE COAST OF MEXICO. THE REMAINDER OF
THE TRACK MODEL GUIDANCE AGREES ON A GENERAL WEST-NORTHWEST MOTION
THROUGH 24 HRS WITH A MORE WESTERLY HEADING THEREAFTER. THE PRIMARY
DIFFERENCES LIE IN THE FORWARD MOTION WITH THE GFDL BEING THE
SLOWEST OF WHILE LBAR AND P91E THE FASTEST.  THE OFFICIAL FORECAST
IS A COMPROMISE BETWEEN CLIPER AND P91E ALTHOUGH CONSIDERABLY SLOWER
...IN LINE WITH THE PREVIOUS PACKAGE.
 
ANALYSES FROM THE CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATE THAT
15-20 KT EASTERLY/SOUTHEASTERLY VERTICAL WIND SHEAR EXTENDS TO NEAR
125W N OF 12N. THE LATEST AVAILABLE NCEP GLOBAL MODEL OUTPUT DEPICTS
THIS FAIRLY WELL AND SUGGESTS THAT THE SHEAR WILL DIMINISH TO NEAR 
10 KT BY 36 HRS. HOWEVER...THE FORECAST TRACK BRINGS THE SYSTEM OVER
GRADUALLY COOLER WATER. THE INTENSITY FORECAST CALLS FOR GRADUAL
STRENGTHENING WITH FERNANDA FORECAST TO REACH HURRICANE STRENGTH BY
72 HRS...IN GOOD AGREEMENT WITH SHIPS. 
 
GUINEY
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     18/0900Z 15.2N 118.6W    35 KTS
12HR VT     18/1800Z 16.0N 120.3W    40 KTS
24HR VT     19/0600Z 16.6N 122.1W    45 KTS
36HR VT     19/1800Z 16.9N 123.8W    55 KTS
48HR VT     20/0600Z 17.2N 125.2W    60 KTS
72HR VT     21/0600Z 17.5N 127.5W    65 KTS
 
 
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