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Tropical Storm PRISCILLA Forecast Discussion Number 4
2013-10-15 04:38:44| National Hurricane Center (East Pacific)
Issued at 800 PM PDT MON OCT 14 2013 000 WTPZ41 KNHC 150238 TCDEP1 TROPICAL STORM PRISCILLA DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL EP162013 800 PM PDT MON OCT 14 2013 THE CLOUD PATTERN OF PRISCILLA HAS LOST SOME ORGANIZATION DURING THE PAST SEVERAL HOURS. ALTHOUGH THERE HAS BEEN A NEW BURST OF DEEP CONVECTION NEAR THE EXPOSED LOW-LEVEL CENTER...THE OVERALL CONVECTIVE MASS HAS SHRUNK AND CLOUD TOP TEMPERATURES HAVE WARMED SOME SINCE EARLIER TODAY. THE INITIAL INTENSITY IS LOWERED TO 35 KT IN ACCORDANCE WITH THE LATEST DVORAK CI NUMBERS FROM TAFB AND SAB. THE INITIAL MOTION ESTIMATE IS DUE NORTH OR 360/07. THE CYCLONE HAS BEEN MOVING NORTHWARD AROUND THE WESTERN PERIPHERY OF A MID-LEVEL RIDGE OVER EASTERN MEXICO AND TOWARD A WEAKNESS TO THE WEST OF THE BAJA CALIFORNIA PENINSULA. HOWEVER...A MID-LEVEL RIDGE IS FORECAST TO BUILD TO THE NORTH OF PRISCILLA SOON...WHICH SHOULD CAUSE THE CYCLONE TO TURN NORTHWESTWARD OR EVEN WEST-NORTHWESTWARD DURING THE NEXT DAY OR TWO. IN 2 TO 3 DAYS...THE TRACK SHOULD BEND TOWARD THE WEST ONCE THE SYSTEM DECOUPLES AND BECOMES EMBEDDED IN THE LOW-LEVEL TRADE WINDS. THE NHC TRACK FORECAST IS SLIGHTLY LEFT AND FASTER THAN THE PREVIOUS ONE...IN THE DIRECTION OF THE MULTI-MODEL CONSENSUS TVCE. MODERATE TO STRONG EASTERLY SHEAR AFFECTING THE CYCLONE IS FORECAST BY THE GLOBAL MODELS TO DECREASE SUBSTANTIALLY IN ABOUT 12 HOURS WHILE PRISCILLA MOVES OVER WARM BUT SLOWLY DECREASING SEA SURFACE TEMPERATURES. DESPITE THE SOMEWHAT MORE FAVORABLE ENVIRONMENT AHEAD...PRISCILLA IS ALREADY INGESTING MORE AND MORE OF A STRATOCUMULUS FIELD INTO ITS CIRCULATION FROM THE NORTH. THIS NEGATIVE FACTOR WOULD LIKELY PRECLUDE ANY SHORT-TERM INTENSIFICATION. WEAKENING LIKELY IN ABOUT 48 HOURS DUE TO A SUBSTANTIAL INCREASE IN WESTERLY SHEAR AND MUCH COOLER WATERS. THE NHC INTENSITY FORECAST IS LOWERED RELATIVE TO THE PREVIOUS ONE AND IS SLIGHTLY ABOVE THE BULK OF THE INTENSITY GUIDANCE. DISSIPATION IS NOW SHOWN SOONER...BY 96 HOURS...IN AGREEMENT WITH THE GLOBAL MODEL SOLUTIONS. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 16.2N 115.8W 35 KT 40 MPH 12H 15/1200Z 16.9N 116.5W 35 KT 40 MPH 24H 16/0000Z 17.6N 117.7W 35 KT 40 MPH 36H 16/1200Z 18.4N 119.0W 30 KT 35 MPH 48H 17/0000Z 19.2N 120.2W 25 KT 30 MPH 72H 18/0000Z 19.5N 122.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 19/0000Z...DISSIPATED $$ FORECASTER KIMBERLAIN
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