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Tropical Depression FIFTEEN-E


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TROPICAL DEPRESSION FIFTEEN-E DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 PM PDT WED SEP 28 2005
 
TROPICAL DEPRESSION 15-E REMAINS A WELL-ORGANIZED TROPICAL CYCLONE
IN TERMS OF THE LOW-LEVEL WIND FIELD... AS NOTED IN 28/1302Z
QUIKSCAT WIND DATA. EVEN THOUGH THE DEPTH AND AMOUNT OF CONVECTION
HAS DECREASED SHARPLY SINCE THIS MORNING... THERE REMAINS A
SIGNIFICANT CONVECTIVE BAND WRAPPING AROUND THE CENTER IN THE
NORTHWEST SEMICIRCLE. THE ADVISORY INTENSITY OF 30 KT IS BASED ON A
CONSENSUS DVORAK SATELLITE INTENSITY ESTIMATE OF T2.0/30 KT FROM
ALL THREE SATELLITE AGENCIES. UPPER-LEVEL REMAINS FAIR TO GOOD IN
ALL QUADRANTS... EXCEPT TO THE NORTHEAST DUE TO UPPER-LEVEL SHEAR.

THE INITIAL MOTION ESTIMATE REMAINS 270/06. THE LOW-LEVEL CENTER IS
A LITTLE DIFFICULT TO ASCERTAIN AS A COUPLE OF SMALL VORTICES HAVE
BEEN NOTED ROTATING CYCLONICALLY AROUND THE SOUTHERN AND EASTERN
QUADRANTS THIS AFTERNOON. THE LAST FEW IMAGES... HOWEVER... SUGGEST
THAT THE DOMINANT CIRCULATION CENTER HAS PULLED UNDERNEATH THE
WELL-DEFINED MID-LEVEL CENTER... AND THAT WAS THE FEATURE USED TO
LOCATE THE CENTER OF TD-15E FOR THIS ADVISORY. THE BROAD EAST-WEST
ORIENTED SUBTROPICAL RIDGE LOCATED ACROSS TEXAS AND NORTHERN MEXICO
IS FORECAST TO REMAIN INTACT THROUGH ABOUT THE NEXT 48 HOURS...
WHICH SHOULD ACT TO KEEP TD-15E MOVING IN A WEST-NORTHWESTWARD
DIRECTION. AFTERWARDS...  ALL OF THE GLOBAL MODELS AND THE GFDL
MODEL ARE IN GOOD AGREEMENT ON A MID-LEVEL SHORTWAVE TROUGH TO DIG
SOUTHWARD FROM THE FAR NORTH PACIFIC AND ERODE THE WESTERN PORTION
OF THE RIDGE. AN ELONGATED MID-LEVEL TROUGH OR A CLOSED LOW IS
FORECAST TO PERSIST OFF THE CALIFORNIA COAST IN 72 TO 120 HOURS...
WHICH IS EXPECTED TO TURN THE CYCLONE MORE NORTHWARD AND POSSIBLY
RESULT IN LANDFALL ALONG THE WEST COAST OF BAJA CALIFORNIA IN
96-120 HOURS. THE MAIN DIFFERENCE BETWEEN THE MODELS REMAINS THE
TIMING AND DEGREE OF EROSION OF THE RIDGE. THE GFDL MODEL ROCKETS
THE CYCLONE NORTHWARD AND HAS IT OVER SOUTHERN UTAH IN 120 HOURS.
THIS IS CLEARLY THE OUTLIER MODEL AT THIS TIME SINCE THE REMAINDER
OF THE MODEL GUIDANCE IS MUCH SLOWER AND KEEPS THE CYCLONE OVER OR
SOUTHWEST OF BAJA CALIFORNIA THROUGHOUT THE FORECAST PERIOD. SINCE
THE GLOBAL MODELS INITIALIZED TD-15E QUITE WELL AT 12Z...  THE
OFFICIAL TRACK IS CLOSE TO THE NHC MODEL CONSENSUS... ONLY SLOWER
DUE TO CONTAMINATION CAUSED BY THE MUCH FASTER GFDL MODEL. 
 
THE VERTICAL SHEAR IS GRADUALLY DECREASING AND IS NOW ABOUT 15 KT
FROM THE NORTHEAST.  BY 48 HOURS... THE SHEAR IS STILL FORECAST TO
DECREASE TO 5 KT OR LESS WHILE THE CYCLONE IS OVER 28-29C SSTS.  AS
A RESULT... INTENSIFICATION TO HURRICANE STRENGTH IS FORECAST...
WHICH REMAINS HIGHER THAN THE SHIPS INTENSITY MODEL... BUT SIMILAR
TO THE GFDL MODEL. BY DAYS 4 AND 5... THE CYCLONE IS FORECAST TO
MOVE OVER MUCH COOLER WATER AND GRADUALLY WEAKEN. HOWEVER... DUE TO
THE SHARP SST-GRADIENT THAT EXISTS WITHIN 100 NMI OF THE WEST COAST
OF BAJA CALFIFORNIA... JUST A SLIGHT DEVIATION RIGHT/LEFT OF TRACK
COULD RESULT IN A SIGNIFICANTLY HIGHER/LOWER INTENSITY AT 72 HOURS
THROUGH 120 HOURS.
 
FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      28/2100Z 17.1N 106.6W    30 KT
 12HR VT     29/0600Z 17.6N 107.7W    35 KT
 24HR VT     29/1800Z 18.3N 109.1W    40 KT
 36HR VT     30/0600Z 19.2N 110.5W    45 KT
 48HR VT     30/1800Z 20.1N 111.5W    55 KT
 72HR VT     01/1800Z 21.7N 112.9W    65 KT
 96HR VT     02/1800Z 23.5N 114.0W    55 KT
120HR VT     03/1800Z 26.0N 114.5W    45 KT

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