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Tropical Depression ERIN Forecast Discussion Number 13
2013-08-18 04:42:10| National Hurricane Center (Atlantic)
Issued at 1100 PM AST SAT AUG 17 2013 000 WTNT45 KNHC 180241 TCDAT5 TROPICAL DEPRESSION ERIN DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052013 1100 PM AST SAT AUG 17 2013 THE LOW-LEVEL STRUCTURE OF ERIN HAS RECENTLY DEGRADED WITH THE CIRCULATION BECOMING ELONGATED FROM NORTHWEST TO SOUTHEAST. IN ADDITION...THE ASSOCIATED DEEP CONVECTION IS FARTHER AWAY FROM THE CENTER. AN ASCAT PASS FROM 2310 UTC SUGGESTED MAXIMUM WINDS OF 30-35 KT...AND GIVEN THE DECREASING DVORAK ESTIMATES AND THE RECENT SATELLITE TRENDS...30 KT IS CHOSEN AS THE INTITAL INTENSITY. SOUTHWESTERLY SHEAR...DRY AIR...AND MARGINAL SEA SURFACE TEMPERATURES SHOULD CAUSE ERIN TO BECOME A REMNANT LOW WITHIN 48 HOURS. THE LATEST NHC INTENSITY FORECAST FOLLOWS THE TREND OF THE PREVIOUS ADVISORY AND IS SIMILAR TO THE GLOBAL MODEL GUIDANCE...WHICH SHOW ERIN DEGENERATING INTO A TROUGH OF LOW PRESSURE BY 72 HOURS. ASCAT DATA SUGGEST THE CENTER OF ERIN HAS MOVED WESTWARD DURING THE PAST FEW HOURS BUT A LONGER-TERM MOTION IS 290/10. A SUBTROPICAL RIDGE REBUILDING OVER THE CENTRAL ATLANTIC APPEARS TO HAVE CAUSED THE LEFTWARD TURN AND SHOULD STEER ERIN ON THIS GENERAL COURSE FOR THE NEXT COUPLE OF DAYS. MODEL GUIDANCE HAS SHIFTED NOTABLY SOUTHWARD ON THIS CYCLE...WITH A FEW MODELS EVEN SHOWING A DUE WESTWARD TRACK. ASSUMING A WEAKER ERIN WOULD BECOME MORE STEERED BY A STRONGER LOW-LEVEL RIDGE...THE NHC FORECAST IS ADJUSTED TO THE SOUTH. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 20.7N 37.7W 30 KT 35 MPH 12H 18/1200Z 21.3N 39.2W 30 KT 35 MPH 24H 19/0000Z 21.9N 41.3W 30 KT 35 MPH 36H 19/1200Z 22.5N 43.6W 25 KT 30 MPH 48H 20/0000Z 23.0N 46.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 21/0000Z...DISSIPATED $$ FORECASTER BLAKE
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