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TROPICAL DEPRESSION THIRTEEN DISCUSSION NUMBER   7
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT MON SEP 23 2002
 
THE CYCLONE CONTINUES TO PRODUCE A LARGE CLUSTER OF DEEP CONVECTION. 
HOWEVER...IT IS BELIEVED THAT THE LOW LEVEL CENTER REMAINS WEST OF 
THE CONVECTION.  THERE IS ALSO SOME QUESTION AS TO WHETHER THE 
CIRCULATION IS CLOSED AS QUIKSCAT DATA FROM LAST EVENING INDICATED 
THE DEPRESSION MAY BE AN OPEN WAVE.  BECAUSE OF THESE UNCERTAINTIES 
THE SYSTEM WILL REMAIN A 30 KT DEPRESSION.  A RECONNAISSANCE PLANE 
WILL INVESTIGATE THE SYSTEM LATER THIS MORNING TO ANSWER THESE 
QUESTIONS.  IF THE PLANE FINDS A TROPICAL STORM IT WILL REQUIRE US 
TO UPGRADE THE TROPICAL STORM WATCHES TO WARNINGS QUICKLY.  
 
THE SYSTEM IS BEING STEERED WESTWARD BY A MID LEVEL RIDGE TO THE 
NORTH AND THE INITIAL MOTION IS ESTIMATED TO BE 280/20 KT. THE 
LATEST GFS MODEL SHIFTED THE FORECAST TRACK WELL NORTH OF THE 
PREVIOUS RUN.  THE GFS SOLUTION MAY BE INFLUENCED BY A WEAKNESS IN 
THE RIDGE CAUSED BY TROPICAL STORM KYLE.  IN ANY CASE...MOST OF THE 
MODEL GUIDANCE SLOW THE SYSTEM DOWN IN ABOUT 48 HOURS...AS DOES THE 
OFFICIAL FORECAST.  THE OFFICIAL FORECAST IS NEAR THE SOUTHERN 
EDGE OF THE MODEL ENVELOPE AND CLOSER TO THE GFDL AND THE PREVIOUS 
ADVISORY. 

THE OUTFLOW REMAINS IMPRESSIVE IN THE NORTHERN SEMICIRCLE AND THE 
SHIPS INTENSITY MODEL FORECASTS A LOW SHEAR ENVIRONMENT.  ASSUMING 
THAT THE PLANE FINDS A CLOSED CIRCULATION....THE FORECAST IS FOR 
GRADUAL STRENGTHENING WHICH IS CONSISTENT WITH THE PREVIOUS ADVISORY 
BUT IS LESS AGGRESSIVE THAN THE SHIPS MODEL.
 
FORECASTER JARVINEN/BROWN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     23/0900Z 12.7N  58.4W    30 KTS
12HR VT     23/1800Z 13.2N  61.4W    35 KTS
24HR VT     24/0600Z 14.0N  64.6W    40 KTS
36HR VT     24/1800Z 14.8N  67.2W    50 KTS
48HR VT     25/0600Z 15.6N  69.3W    55 KTS
72HR VT     26/0600Z 17.0N  72.5W    65 KTS
 
 
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