Tropical Storm ERIN

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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
 
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