258 
 WTNT45 KNHC 152032
 TCDAT5
  
 TROPICAL STORM ERIN DISCUSSION NUMBER   4
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052013
 500 PM AST THU AUG 15 2013
  
 THE CONVECTIVE PATTERN OF ERIN HAS EVOLVED INTO ONE THAT FEATURES
 MORE BANDING AWAY FROM THE CENTER AND WARMER CLOUD TOPS NEAR THE
 CENTER ITSELF. THE INITIAL INTENSITY REMAINS 35 KT BASED ON THE
 LATEST TAFB DVORAK ESTIMATE. THE INTENSITY FORECAST REASONING
 REMAINS UNCHANGED. FOR THE NEXT COUPLE OF DAYS...THE CYCLONE WILL
 BE MOVING THROUGH A MOIST LOW-SHEAR ENVIRONMENT WITH SSTS OF
 26-27C...WHICH SHOULD SUPPORT MODEST STRENGTHENING. LATER IN THE
 PERIOD...ALTHOUGH SSTS INCREASE...ERIN WILL BE MOVING INTO A DRIER
 MORE STABLE ATMOSPHERE...AND WEAKENING IS EXPECTED. THE NHC
 INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ONE AND IS CLOSE TO
 THE INTENSITY CONSENSUS THROUGH 72 HOURS AND THEN FOLLOWS THE TREND
 OF THE DYNAMICAL MODELS...SHOWING GRADUAL WEAKENING.
 
 THE INITIAL MOTION ESTIMATE IS 290/12...AS THE CYCLONE APPEARS TO
 HAVE TURNED A BIT TO THE RIGHT DURING THE PAST FEW HOURS. THERE HAS
 BEEN A SIZEABLE NORTHWARD SHIFT IN NEARLY ALL OF THE TRACK MODEL
 GUIDANCE THIS CYCLE. THE GLOBAL MODELS NOW SHOW A DEEPER
 REPRESENTATION OF ERIN MOVING MORE INTO A WEAKNESS IN THE
 SUBTROPICAL RIDGE TO THE SOUTH OF A MID/UPPER-LEVEL LOW THAT WILL
 BE MEANDERING SOUTH OF THE AZORES. AS A RESULT...THE MODELS SHOW
 ERIN GAINING MORE LATITUDE DURING THE FIRST 72 HOURS OR SO. AFTER
 THAT...A TURN BACK TOWARD THE LEFT IS SHOWN BY MOST OF THE MODELS
 AS THE CYCLONE WEAKENS. FOR THIS CYCLE A NORTHWARD ADJUSTMENT HAS
 BEEN MADE TO THE NHC FORECAST...BUT THE NHC TRACK IS ON THE
 SOUTHERN SIDE OF THE GUIDANCE ENVELOPE...ESPECIALLY AT DAYS 3
 THROUGH 5. FURTHER ADJUSTMENTS WILL LIKELY BE NECESSARY IF THIS
 NORTHWARD TREND IN THE GUIDANCE PERSISTS IN FUTURE CYCLES.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  15/2100Z 15.0N  27.5W   35 KT  40 MPH
  12H  16/0600Z 15.6N  29.6W   40 KT  45 MPH
  24H  16/1800Z 16.7N  32.0W   45 KT  50 MPH
  36H  17/0600Z 17.5N  34.2W   45 KT  50 MPH
  48H  17/1800Z 18.3N  36.3W   50 KT  60 MPH
  72H  18/1800Z 19.0N  40.5W   50 KT  60 MPH
  96H  19/1800Z 19.5N  44.5W   45 KT  50 MPH
 120H  20/1800Z 20.0N  49.0W   35 KT  40 MPH
  
 $$
 FORECASTER BRENNAN