000 WTPZ43 KNHC 200835 TCDEP3 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