Tropical Storm GREG
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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
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FORECASTER WROE/STEWART
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