ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM GREG DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL EP072011 200 PM PDT FRI AUG 19 2011 GREG CONTINUES TO WEAKEN OVER COOLER WATERS. CLOUD TOPS NEAR THE CENTER HAVE WARMED...AND DEEP CONVECTION SURROUNDING THE INNER CORE HAS DECREASED SUBSTANTIALLY IN COVERAGE DURING THE PAST SIX HOURS...REVEALING THE LOW LEVEL CIRCULATION CENTER. CURRENT SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB CAME IN AT 65 AND 55 KT...RESPECTIVELY...THOUGH DATA-T NUMBERS GAVE SIGNIFICANTLY LOWER STRENGTHS OF 45 AND 40 KT..RESPECTIVELY. THE INITIAL INTENSITY HAS BEEN SET AT 50 KT...ESSENTIALLY AN AVERAGE OF THE DVORAK NUMBERS. GREG WILL CONTINUE TO WEAKEN OVER INCREASINGLY COOLER WATERS DURING THE NEXT COUPLE OF DAYS. THE CORE OF THE CYCLONE IS SITTING OVER SSTS OF APPROXIMATELY 24.5C...AND SSTS WILL BE COOLING TO NEAR 23C TOMORROW. THE OFFICIAL FORECAST CALLS FOR GREG TO WEAKEN INTO A DEPRESSION SATURDAY NIGHT AND TO A REMNANT LOW ON SUNDAY AFTERNOON. THE OFFICIAL FORECAST CLOSELY FOLLOWS THE WEAKENING RATE OF SHIPS GUIDANCE...BUT GIVEN THE COOLING SSTS ALONG THE TRACK...FASTER WEAKENING IS POSSIBLE. THE INITIAL MOTION IS 280 DEGREES AT 10 KNOTS. THE TRACK HAS BEEN SHIFTED SLIGHTLY TO THE NORTH FROM THE PRIOR PACKAGE GIVEN A GREATER DEGREE OF NORTHWARD DRIFT THAN EXPECTED. HOWEVER...GREG WILL FOLLOW A GENERAL WESTWARD MOTION OVER THE NEXT COUPLE OF DAYS UNDER THE STEERING INFLUENCE OF THE NORTHEAST PACIFIC SUBTROPICAL RIDGE. AS THE SYSTEM WEAKENS AND BECOMES INCREASINGLY SHALLOW...A SLIGHT TURN TO THE WEST-SOUTHWEST IS EXPECTED ON SUNDAY. EVEN WITH THE NORTHWARD SHIFT IN THE FORECAST...THE TRACK FORECAST IS ON THE LEFT OR SOUTH SIDE SIDE OF THE GUIDANCE ENVELOPE. FORECAST POSITIONS AND MAX WINDS INIT 19/2100Z 19.6N 117.0W 50 KT 60 MPH 12H 20/0600Z 19.7N 118.6W 40 KT 45 MPH 24H 20/1800Z 19.7N 120.5W 35 KT 40 MPH 36H 21/0600Z 19.6N 122.2W 30 KT 35 MPH 48H 21/1800Z 19.3N 123.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 22/1800Z 18.7N 126.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 23/1800Z...DISSIPATED $$ FORECASTER WROE/STEWART NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:44:15 UTC