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Tropical Depression EIGHT (Text)


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TTAA00 KNHC DDHHMM
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082009
500 AM AST SAT SEP 26 2009
 
WHILE DEEP CONVECTION HAS INCREASED OVER THE PAST FEW HOURS...
GEOSTATIONARY IMAGERY AND AN AMSR-E PASS FROM AROUND 0400 UTC
SUGGEST THAT THE LOW-LEVEL CENTER IS LOCATED ON THE SOUTHWESTERN
EDGE OF THE CONVECTION. THIS STRUCTURE IS LIKELY DUE TO THE 10-15
KT OF SOUTHWESTERLY SHEAR ANALYZED OVER THE CYCLONE BY UW-CIMSS AND
THE SHIPS MODEL. DVORAK CI-NUMBERS WERE 1.5 AND 2.0 FROM SAB AND
TAFB...RESPECTIVELY...AND THE INITIAL INTENSITY IS HELD AT 30 KT
FOR THIS ADVISORY. CONDITIONS WILL BE ONLY MARGINALLY FAVORABLE FOR
INTENSIFICATION OVER THE NEXT 2-3 DAYS. SSTS WILL BE 26-27C...AND
THE SHIPS MODEL SHOWS THE SHEAR DECREASING BELOW 15 KT ONLY FOR A
BRIEF PERIOD FROM 12 TO 24 HOURS. GIVEN THIS...THE OFFICIAL
FORECAST HOLDS THE INTENSITY AT 30 KT THROUGH 24 HOURS AND THEN
SHOWS A GRADUAL WEAKENING. HOWEVER...IT IS POSSIBLE THAT THE SYSTEM
COULD BRIEFLY REACH TROPICAL STORM STATUS DURING THE NEXT DAY OR
SO. 
 
THE INITIAL MOTION ESTIMATE IS 300/12...A LITTLE TO THE LEFT OF THE
PREVIOUS ADVISORY. MOST OF THE TRACK GUIDANCE INDICATES THAT THE
CYCLONE WILL ROUND THE WESTERN EDGE OF THE SUBTROPICAL RIDGE AND
TURN TOWARD THE NORTHWEST OVER THE NEXT COUPLE OF DAYS. BEYOND THAT
TIME...THE GFS...NOGAPS AND HWRF SHOW THE DEPRESSION OR ITS REMNANTS
TURNING NORTHWARD AHEAD OF A FRONT...WHILE THE UKMET...ECMWF...AND
THE MEDIUM BAM SUGGEST THAT WHAT IS LEFT OF THE CYCLONE WILL TURN
WESTWARD. THE OFFICIAL FORECAST IS SOUTH OF THE PREVIOUS ONE FOR
THE FIRST 24 HOURS DUE TO THE INITIAL MOTION...AND IS AN UPDATE OF
THE PREVIOUS FORECAST BEYOND THAT TIME. AT DAY 3 ONLY A SLOW
NORTHWESTWARD MOTION IS INDICATED DUE TO THE LARGE SPREAD IN THE
GUIDANCE.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      26/0900Z 17.6N  33.8W    30 KT
 12HR VT     26/1800Z 18.7N  35.3W    30 KT
 24HR VT     27/0600Z 20.2N  36.9W    30 KT
 36HR VT     27/1800Z 21.6N  38.1W    25 KT
 48HR VT     28/0600Z 23.1N  39.3W    25 KT
 72HR VT     29/0600Z 24.5N  40.5W    20 KT...REMNANT LOW
 96HR VT     30/0600Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 
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Page last modified: Thursday, 31-Dec-2009 12:09:11 UTC