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Tropical Storm COSME Forecast Discussion Number 8
2013-06-25 10:41:09| National Hurricane Center (East Pacific)
Issued at 200 AM PDT TUE JUN 25 2013 000 WTPZ43 KNHC 250841 TCDEP3 TROPICAL STORM COSME DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP032013 200 AM PDT TUE JUN 25 2013 MICROWAVE AND INFRARED SATELLITE IMAGERY INDICATE THAT THE INTERNAL AND OVERALL CONVECTIVE CLOUD STRUCTURES HAVE CHANGED LITTLE SINCE THE PREVIOUS ADVISORY. IN FACT...UW-CIMSS ADT ESTIMATES HAVE LEVELED OFF AT ABOUT T3.6/57 KT FOR MORE THAN 12 HOURS. THE CLOUD PATTERN HAS RECENTLY BECOME ELONGATED NORTH-TO-SOUTH AND THE CENTER IS LOCATED NEAR THE WESTERN EDGE OF THE CONVECTIVE CLOUD MASS. A BLEND OF DVORAK T-NUMBERS FROM TAFB AND SAB...RECENT ADT VALUES... AND CIRA AND CIMSS AMSU INTENSITY ESTIMATES OF 47 KT AND 49 KT... RESPECTIVELY...YIELDS AN AVERAGE INTENSITY OF 55 KT...WHICH WAS USED FOR THIS ADVISORY. THE UPPER-LEVEL OUTFLOW PATTERN REMAINS SYMMETRICAL AND CONTINUES TO IMPROVE. MICROWAVE IMAGERY AND CONTINUITY WITH THE PREVIOUS FORECAST TRACK WERE USED TO DETERMINE THE LOCATION OF COSME...WHICH YIELDS AN INITIAL MOTION ESTIMATE OF 290/14 KT. THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING. COSME IS EXPECTED TO MOVE WEST-NORTHWESTWARD FOR THE NEXT 72 HOURS ALONG THE SOUTHWESTERN PERIPHERY OF A STRONG AND WESTWARD-EXPANDING MID-LEVEL SUBTROPICAL RIDGE CURRENTLY LOCATED OVER NORTHERN MEXICO AND THE SOUTHWESTERN UNITED STATES. AFTER THAT...A RAPIDLY WEAKENING COSME SHOULD BE STEERED GENERALLY WESTWARD BY THE LOW-LEVEL TRADE WIND FLOW. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND IS SITUATED ALONG THE SOUTHERN EDGE OF THE TRACK GUIDANCE SUITE...AND FOLLOWS THE SPEED OF THE CONSENSUS MODEL TVCA. UW-CIMSS SHEAR ANALYSES OVER THE PAST 12 HOURS INDICATE THAT COSME HAS AGAIN MOVED INTO A MODERATELY UNFAVORABLE MID-LEVEL SHEAR ENVIRONMENT...WHICH MAY BE THE CAUSE OF THE RECENT DISHEVELED LOOKING INNER-CORE CONVECTIVE CLOUD PATTERN. HOWEVER...THE CYCLONE IS EXPECTED TO MOVE INTO MORE FAVORABLE MID- AND UPPER-LEVEL FLOW REGIMES LATER TODAY...ALLOWING COSME TO STRENGTHEN INTO A HURRICANE BEFORE THE SYSTEM REACHES SUB-25C SSTS IN ABOUT 36 HOURS. STEADY TO RAPID WEAKENING IS THEN FORECAST TO BEGIN AFTER THE CYCLONE MOVES OVER MUCH COOLER WATERS BY 48 HOURS...AND COSME IS EXPECTED TO BECOME A NON-CONVECTIVE REMNANT LOW BETWEEN 72 AND 96 HOURS. THE NHC INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS INTENSITY FORECAST...AND REMAINS CLOSE TO A BLEND OF THE DECAY-SHIPS AND LGEM INTENSITY MODELS. THE EXTENSIVE 12-FT SEAS RADII IN THE EASTERN SEMICIRCLE PROVIDED BY THE TAFB IS THE RESULT OF LONG-FETCH SOUTHERLY CROSS-EQUATORIAL FLOW GENERATING LARGE SWELLS...WHICH WILL IN TURN AFFECT MUCH OF THE PACIFIC COAST OF MEXICO AND THE BAJA PENINSULA DURING THE NEXT COUPLE OF DAYS AS THE LARGE SWELLS PROPAGATE NORTHWARD. FORECAST POSITIONS AND MAX WINDS INIT 25/0900Z 16.5N 109.5W 55 KT 65 MPH 12H 25/1800Z 17.2N 111.5W 65 KT 75 MPH 24H 26/0600Z 17.9N 113.9W 75 KT 85 MPH 36H 26/1800Z 18.5N 116.1W 60 KT 70 MPH 48H 27/0600Z 19.3N 118.7W 50 KT 60 MPH 72H 28/0600Z 20.4N 124.1W 35 KT 40 MPH 96H 29/0600Z 20.9N 129.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 30/0600Z 20.9N 134.3W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ FORECASTER STEWART
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