Tropical Depression FOUR-E

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TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 AM PDT SUN JUL 06 2003
 
THE INITIAL POSITION OF TD-04E IS RATHER UNCERTAIN DUE TO CIRRUS
BLOWOFF TO THE EAST WHICH IS OBSCURING THE LOW-LEVEL CENTER. HAVING
SAID THAT...THE CYCLONE LOCATION FOR THIS ADVISORY WAS BASED ON
CONTINUITY WITH THE PREVIOUS FORECAST TRACK USING AN INITIAL MOTION
OF 295/10...WHICH IS CLOSE TO THE AVERAGE MOTION OF THE NHC MODEL
GUIDANCE...AND ASSUMING THE CENTER IS NEAR THE EAST SIDE OF THE
DEEPEST CONVECTION DUE TO EASTERLY SHEAR. 
 
LITTLE CHANGE WAS MADE TO THE PREVIOUS FORECAST TRACK OTHER THAN TO
BRING IT SOUTHWARD JUST A TAD AND ALSO TO ADD A 120-HOUR FORECAST
POSITION. THE PREVIOUS SHIPS INTENSITY FORECAST HAD THE CYCLONE
DISSIPATING IN 96-120 HOURS. HOWEVER...THAT OUTPUT WAS BASED ON THE
MUCH FASTER MEDIUM BAM MODEL. THE OFFICIAL FORECAST MOVES THE
DEPRESSION SLOWER THAN ALL THE BAM MODELS AND IS A BLEND OF THE
GFS...UKMET...AND THE CANADIAN MODEL TRACKS BUT USING ROUGHLY THE
SPEED OF THE GFS MODEL. ALL OF THE GLOBAL MODELS MAINTAIN A FAIRLY
STRONG E-W ORIENTED SUBTROPICAL RIDGE TO THE NORTH OF THE CYCLONE
THROUGH 96 HOURS...WITH GRADUAL EROSION OF THE WESTERN PERIPHERY OF
THE RIDGE BY 120 HOURS. HOWEVER...WHETHER OR NOT THE CYCLONE MOVES
POLEWARD BY 120 HOURS WILL BE DETERMINED BY THE EXACT STRENGTH AND
VERTICAL DEPTH OF THE SYSTEM AT THAT TIME. THE NOGAPS MODEL WAS
DISCOUNTED SINCE IT MOVES THE CYCLONE VERY LITTLE FOR THE FIRST 48
HOURS FOR NO OBVIOUS PHYSICAL REASONS...ESPECIALLY GIVEN THE STRONG
RIDGE TO THE NORTH AND THE PAST MOTION OF AT LEAST 10 KT.
 
THE CYCLONE IS EXPECTED TO MOVE OVER SUB-26C SSTS IN ABOUT 24 HOURS
WHICH SHOULD HELP TO PRECLUDE ANY SIGNIFICANT AND/OR RAPID
INTENSIFICATION FROM OCCURRING. HOWEVER...WEAKENING SHEAR OF LESS
THAN 5 KT SHOULD ALLOW GOOD OUTFLOW TO DEVELOP...WHICH IN TURN
SHOULD ALLOW FOR AT LEAST SOME MODEST INTENSIFICATION TO OCCUR AS
INDICATED BY THE SHIPS MODEL INTENSITY FORECAST.
 
FORECASTER STEWART
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/1500Z 14.3N 117.5W    30 KT
 12HR VT     07/0000Z 14.9N 118.9W    35 KT
 24HR VT     07/1200Z 15.6N 120.6W    40 KT
 36HR VT     08/0000Z 16.2N 122.5W    45 KT
 48HR VT     08/1200Z 16.8N 124.4W    45 KT
 72HR VT     09/1200Z 17.8N 128.0W    40 KT
 96HR VT     10/1200Z 19.0N 132.0W    35 KT
120HR VT     11/1200Z 20.0N 136.0W    30 KT...DISSIPATING
 
 
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