Tropical Depression THIRTEEN-E

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TROPICAL DEPRESSION THIRTEEN-E DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP132007
200 AM PDT THU SEP 20 2007
 
THERE ARE ONLY A FEW REMAINING CELLS OF DEEP CONVECTION ASSOCIATED
WITH THE DEPRESSION.  THE HIGHEST BELIEVABLE WIND VECTORS ON A
QUIKSCAT PASS FROM SEVERAL HOURS AGO WERE NEAR 30 KT...SO THE
INITIAL INTENSITY IS MAINTAINED AT 30 KT FOR THIS ADVISORY.  THE
CYCLONE IS SITUATED OVER MARGINAL SEA SURFACE TEMPERATURES AND IN
AN ENVIRONMENT OF MODEST EASTERLY SHEAR.  ALTHOUGH SOME OF THE
NUMERICAL GUIDANCE INDICATES THAT THE SYSTEM WILL STRENGTHEN A
LITTLE AS IT LOOPS SOUTHWARD TOWARD SLIGHTLY WARMER WATERS...THE
CURRENT TREND OF THE CLOUD PATTERN SUGGESTS WEAKENING.  AS A
COMPROMISE...THE OFFICIAL FORECAST MAINTAINS THE DEPRESSION AT ITS
CURRENT STRENGTH FOR ABOUT 24 HOURS BEFORE SHOWING WEAKENING.
HOWEVER...IF THE SYSTEM DOES NOT REGENERATE SIGNIFICANT DEEP
CONVECTION BY LATER TODAY...THE TROPICAL CYCLONE COULD DISSIPATE
MUCH SOONER THAN SHOWN BY THIS FORECAST.
 
FIXES FROM MICROWAVE AND CONVENTIONAL SATELLITE IMAGES GIVE A SLOW
WEST-NORTHWESTWARD MOTION OF ABOUT 285/6.  GLOBAL MODEL FORECASTS
FOR THE NEXT FEW DAYS DEPICT A LOW- TO MID-LEVEL ANTICYCLONE TO THE
NORTHWEST OF THE DEPRESSION AND A TROUGH EXTENDING TO THE NORTHEAST
OF IT...TOWARD AN INTENSIFYING CYCLONE NEAR THE SOUTHERN
CALIFORNIA-NORTHERN BAJA CALIFORNIA BORDER.  THE RESULT IS A WEAK
STEERING CURRENT.  THE OFFICIAL FORECAST TRACK SHOWS A VERY SLOW
LOOPING MOTION AS IN THE PREVIOUS NHC FORECAST.  AN ALTERNATE
SCENARIO IS FOR A VERY WEAK AND SHALLOW SYSTEM TO BE STEERED MOSTLY
WESTWARD BY THE NEAR-SURFACE TRADE WINDS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0900Z 17.8N 129.8W    30 KT
 12HR VT     20/1800Z 17.6N 130.4W    30 KT
 24HR VT     21/0600Z 17.0N 130.8W    30 KT
 36HR VT     21/1800Z 16.6N 130.4W    25 KT
 48HR VT     22/0600Z 16.7N 129.8W    20 KT...REMNANT LOW
 72HR VT     23/0600Z 17.0N 129.0W    20 KT...REMNANT LOW
 96HR VT     24/0600Z 17.5N 128.5W    20 KT...REMNANT LOW
120HR VT     25/0600Z...DISSIPATED
 
$$
FORECASTER PASCH
 
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