000 WTNT45 KNHC 170841 TCDAT5 TROPICAL STORM ERIN DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052013 500 AM AST SAT AUG 17 2013 THE CENTER OF ERIN IS AT LEAST PARTLY EXPOSED NEAR THE SOUTHWESTERN EDGE OF THE MAIN CONVECTIVE CLUSTER DUE TO 15 KT OF SOUTHWESTERLY VERTICAL WIND SHEAR...AND THE CONVECTION IS SOMEWHAT FARTHER FROM THE CENTER THAN 6 HOURS AGO. THERE IS NO RECENT DATA FROM NEAR THE CENTER...SO THE INITIAL INTENSITY IS HELD AT 35 KT...WHICH IS ABOVE THE SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB. THE INITIAL MOTION IS 300/13. THERE IS NO CHANGE TO THE TRACK FORECAST PHILOSOPHY FROM THE PREVIOUS ADVISORY. A GRADUALLY STRENGTHENING SUBTROPICAL RIDGE SHOULD STEER ERIN GENERALLY WEST-NORTHWESTWARD FOR THE NEXT 24-36 HOUR. THIS SHOULD BE FOLLOWED BY A TURN MORE TO THE LEFT AROUND A STRONGER LOW-LEVEL RIDGE THROUGH 72H. THEREAFTER...A TURN BACK TO THE NORTHWEST IS FORECAST WHEN ERIN...OR ITS REMNANTS...MOVES TOWARD A BREAK IN THE RIDGE BETWEEN 50W-60W. THE NEW FORECAST TRACK IS SHIFTED A LITTLE TO THE NORTH OF THE PREVIOUS TRACK IN BEST AGREEMENT WITH THE ECMWF... UKMET...CANADIAN..AND NAVGEM MODELS. THE TRACK LIES WELL TO THE LEFT OF THE GFS...WHICH RECURVES ERIN THROUGH THE BREAK IN THE RIDGE. ERIN IS CURRENTLY OVER SEA SURFACE TEMPERATURES OF 25C-26C. WHILE THE FORECAST TRACK TAKES THE CYCLONE OVER WARMER WATER...THE CYCLONE IS MOVING INTO A VERY DRY MID/UPPER-LEVEL AIR MASS AS SEEN IN WATER VAPOR AND METEOSAT AIR MASS IMAGERY. IN ADDITION...THE SOUTHWESTERLY SHEAR IS EXPECTED TO GRADUALLY INCREASE DURING THE FORECAST PERIOD. THE NEW INTENSITY FORECAST IS THE SAME AS THE PREVIOUS FORECAST IN CALLING FOR ERIN TO WEAKEN TO A DEPRESSION IN ABOUT 36 HOURS AND TO DEGENERATE TO A REMNANT LOW IN ABOUT 96 HOURS. AN ALTERNATIVE SCENARIO IS THAT ERIN DISSIPATES EARLIER THAN CURRENTLY FORECAST...AS SHOWN BY ALL OF THE GLOBAL MODELS EXCEPT THE GFS. FORECAST POSITIONS AND MAX WINDS INIT 17/0900Z 18.9N 35.6W 35 KT 40 MPH 12H 17/1800Z 19.7N 37.1W 35 KT 40 MPH 24H 18/0600Z 20.4N 38.9W 35 KT 40 MPH 36H 18/1800Z 20.9N 40.8W 30 KT 35 MPH 48H 19/0600Z 21.4N 43.1W 30 KT 35 MPH 72H 20/0600Z 23.0N 48.0W 30 KT 35 MPH 96H 21/0600Z 25.5N 52.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 22/0600Z...DISSIPATED $$ FORECASTER BEVEN