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Tropical Storm ERIN Forecast Discussion Number 12
2013-08-17 22:31:29| National Hurricane Center (Atlantic)
Issued at 500 PM AST SAT AUG 17 2013 000 WTNT45 KNHC 172031 TCDAT5 TROPICAL STORM ERIN DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052013 500 PM AST SAT AUG 17 2013 THE LOW-LEVEL CENTER OF ERIN CONTINUES TO BE EXPOSED...AND IS LOCATED SOUTH OF A SMALL AREA OF DEEP CONVECTION. THE INITIAL INTENSITY REMAINS 35 KT...BUT ERIN SHOULD WEAKEN TO A DEPRESSION SOON IN AN ENVIRONMENT OF SUB-26C WATER AND IN SOUTHWESTERLY SHEAR OF AROUND 15 KT. WHILE THE CYCLONE WILL BE MOVING OVER SLIGHTLY WARMER WATERS IN THE NEXT 2-3 DAYS...A DRY STABLE AIRMASS AND MODERATE SHEAR SHOULD RESULT IN EVENTUAL WEAKENING TO A REMNANT LOW. THE NHC FORECAST SHOWS REMNANT LOW STATUS IN 3 DAYS AND DISSIPATION AT DAY 4...BUT THIS COULD OCCUR SOONER AS SHOWN BY SEVERAL MODELS. ERIN HAS CONTINUED TO MOVE TOWARD THE NORTHWEST OVER THE PAST FEW HOURS...LIKELY DUE TO THE INFLUENCE OF A DEEP-LAYER LOW SOUTH OF THE AZORES. RECENT SATELLITE IMAGES SHOW THAT ERIN HAS TURNED BACK TOWARD THE LEFT...AND THE INITIAL MOTION ESTIMATE IS 315/11. THE TRACK MODEL GUIDANCE IS INSISTENT ON ERIN TURNING BACK TOWARD THE WEST-NORTHWEST IN THE NEXT DAY OR SO AS IT COMES UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE BUILDING TO THE NORTH AND ANOTHER CUTOFF LOW CURRENTLY LOCATED NEAR 24N/49W. IF ERIN SURVIVES LONG ENOUGH...IT WILL LIKELY TURN BACK TOWARD THE NORTHWEST INTO ANOTHER WEAKNESS IN THE RIDGE THAT DEVELOPS BY 72 HOURS. THE NHC FORECAST HAS AGAIN BEEN ADJUSTED NORTHWARD AND IS FASTER THAN THE PREVIOUS ONE TO ACCOUNT FOR THE INITIAL POSITION AND MOTION. THE NHC TRACK LIES NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE AND CLOSE TO THE FSU SUPERENSEMBLE. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 21.0N 37.0W 35 KT 40 MPH 12H 18/0600Z 21.5N 38.3W 30 KT 35 MPH 24H 18/1800Z 22.2N 40.4W 30 KT 35 MPH 36H 19/0600Z 23.0N 42.7W 30 KT 35 MPH 48H 19/1800Z 24.0N 45.0W 30 KT 35 MPH 72H 20/1800Z 26.5N 49.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 21/1800Z...DISSIPATED $$ FORECASTER BRENNAN
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