[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 151440
TCDAT5

TROPICAL STORM ERIN DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052013
1100 AM AST THU AUG 15 2013

THE SATELLITE PRESENTATION OF THE CYCLONE HAS CONTINUED TO IMPROVE
OVER THE PAST FEW HOURS. INFRARED IMAGERY SHOWS VERY COLD CLOUD
TOPS SITUATED NEAR AND TO THE SOUTH OF THE ESTIMATED CENTER
POSITION...WITH A SMALL BANDING FEATURE EXTENDING TO THE SOUTHWEST.
THE INITIAL INTENSITY OF 35 KT IS SUPPORTED BY A BLEND OF THE
LATEST OBJECTIVE AND SUBJECTIVE DVORAK ESTIMATES AND A 1102 UTC
ASCAT-A PASS THAT SHOWED WINDS OF 32 KT. ERIN IS EXPECTED TO BE IN
AN ENVIRONMENT THAT SUPPORTS SOME STRENGTHENING DURING THE NEXT
COUPLE OF DAYS WITH SSTS OF 26-27C...LOW SHEAR...AND A MOIST
ENVIRONMENT. BY DAY 3...THE SYSTEM WILL BE MOVING INTO A DRIER AND
MORE STABLE ATMOSPHERIC ENVIRONMENT...WHICH SHOULD RESULT IN
WEAKENING. THE GLOBAL MODELS AND THE HWRF SHOW A WEAK OR
DISSIPATING SYSTEM BY DAY 5...HOWEVER THE SHIPS AND LGEM SHOW
LITTLE CHANGE IN INTENSITY OR EVEN STRENGTHENING. THE OFFICIAL
FORECAST LEANS A LITTLE TOWARD THE WEAKER SOLUTION AT DAYS 4 AND 5.

THE AFOREMENTIONED ASCAT PASS WAS ALSO HELPFUL IN LOCATING THE
CENTER OF ERIN...WHICH IS A LITTLE SOUTH AND WEST OF PREVIOUS
ESTIMATES. BASED ON A SOUTHWESTWARD ADJUSTMENT OF THE CENTER
POSITION THE INITIAL MOTION ESTIMATE IS 285/13. ERIN IS CURRENTLY
BEING STEERED BY A NARROW SUBTROPICAL RIDGE TO ITS NORTH...AND THE
GUIDANCE IS IN GOOD AGREEMENT ON THIS MOTION CONTINUING FOR THE
NEXT COUPLE OF DAYS. BY DAY 3...THE SPREAD IN THE GUIDANCE
INCREASES. ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE THE GFDL...
GFDL ENSEMBLE MEAN...ECMWF AND UKMET SHOW A NORTHWESTWARD OR
WEST-NORTHWESTWARD MOTION. THE FIM...GFS...GFS ENSEMBLE MEAN AND
HWRF ALL SHOW A WESTWARD TRACK...CONSISTENT WITH A SHALLOWER SYSTEM
BEING STEERED BY THE LOW-LEVEL FLOW. THE NHC FORECAST AT DAYS 3
THROUGH 5 CONTINUES TO FOLLOW THIS SOUTHERN CAMP OF MODELS AND IS
LARGELY AN UPDATE OF THE PREVIOUS NHC TRACK.


FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z 14.4N  26.5W   35 KT  40 MPH
 12H  16/0000Z 15.0N  28.6W   40 KT  45 MPH
 24H  16/1200Z 15.7N  31.2W   45 KT  50 MPH
 36H  17/0000Z 16.7N  33.5W   45 KT  50 MPH
 48H  17/1200Z 17.4N  35.8W   50 KT  60 MPH
 72H  18/1200Z 18.0N  40.0W   50 KT  60 MPH
 96H  19/1200Z 18.0N  44.5W   45 KT  50 MPH
120H  20/1200Z 18.0N  49.0W   35 KT  40 MPH

$$
FORECASTER BRENNAN


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