218 
 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