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TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER  10
NATIONAL WEATHER SERVICE MIAMI FL
2 PM PDT THU JUL 11 2002
 
RIGHT ON SCHEDULE LIKE THE PAST 2 DAYS...TROPICAL DEPRESSION FOUR-E 
HAS UNDERGONE A BURSTING PHASE. VISIBLE SATELLITE IMAGERY INDICATES 
THE CENTER OF THE ELONGATED LOW-LEVEL CIRCULATION MAY BE CLOSER TO 
THE DEEP CONVECTION...SO THE INITIAL POSITION WAS ADJUSTED A LITTLE 
FARTHER TO THE SOUTH AS COMPARED TO THE PREVIOUS TWO ADVISORY 
POSITIONS. THE INITIAL INTENSITY WAS INCREASED TO 30 KT BASED ON 
DVORAK SATELLITE INTENSITY ESTIMATES OF 45 KT...35 KT AND 30 KT FROM 
TAFB...SAB...AND AFWA...RESPECTIVELY. HOWEVER...THE INTENSITY WAS 
HELD DOWN SLIGHTLY...LIKE THIS SAME TIME YESTERDAY...DUE TO THE 
UNCERTAINTY IN THE EXACT LOCATION OF THE LOW-LEVEL CENTER AND THE 
INTERMITTENT NATURE OF THE INNER-CORE CONVECTION THE PAST 3 DAYS.
 
THE INITIAL MOTION ESTIMATE IS 280/09.  THERE IS CONSIDERABLY MORE 
SPREAD IN THE MODEL GUIDANCE NOW THAN DURING THE PAST 24 HOURS. 
HOWEVER...THE GENERAL TENDENCY IN THE MODEL GUIDANCE...EXCEPT FOR 
THE GFDN AND GFDL MODELS...IS FOR THE CYCLONE TO TRACK WESTWARD FOR 
THE NEXT 24 HOURS AND THEN TURN MORE TOWARD THE WEST-NORTHWEST OR 
NORTHWEST AS A MID- TO UPPER-LEVEL TROUGH DIGS SOUTHWARD AND ERODES 
THE SUBTROPICAL RIDGE TO THE NORTH. THE GFDL AND GFDN MODELS TAKE 
THE DEPRESSION ALMOST IMMEDIATELY TO THE NORTHWEST...BUT THOSE 
SCENARIOS WERE DISCOUNTED DUE TO (A) THE STRENGTH OF THE SUBTROPICAL 
RIDGE TO THE NORTH AND (B) THE NORTHERLY UPPER-LEVEL SHEAR.  THE 
OFFICIAL TRACK IS CLOSE TO THE PREVIOUS TWO FORECAST TRACKS AND 
CLOSELY FOLLOWS THE AVN AND AVN 10-MEMBER ENSEMBLE AVERAGE MODELS.
 
THE SHIPS INTENSITY MODEL KEEPS THE CYCLONE BELOW HURRICANE STRENGTH 
DESPITE DECREASING VERTICAL SHEAR AND SSTS ABOVE 28C. THE NEW GFDL 
RUN BRINGS THE SYSTEM UP TO 91 KT IN ABOUT 72 HOURS. GIVEN THE 
DECREASING SHEAR EXPECTED AFTER 36 HOURS...THE OFFICIAL INTENSITY 
FORECAST BRINGS THE CYCLONE UP TO HURRICANE STRENGTH IN 48 HOURS AND 
THEN MAINTAINS THAT INTENSITY DUE TO THE SYSTEM TRACKING OVER SUB- 
26C SSTS BY 72 HOURS.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     11/2100Z 14.5N 111.9W    30 KTS
12HR VT     12/0600Z 14.7N 113.3W    35 KTS
24HR VT     12/1800Z 15.0N 115.0W    45 KTS
36HR VT     13/0600Z 15.9N 116.4W    55 KTS
48HR VT     13/1800Z 17.0N 117.2W    65 KTS
72HR VT     14/1800Z 18.5N 118.0W    65 KTS
 
 
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