[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 180241
TCDAT5

TROPICAL DEPRESSION ERIN DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052013
1100 PM AST SAT AUG 17 2013

THE LOW-LEVEL STRUCTURE OF ERIN HAS RECENTLY DEGRADED WITH THE
CIRCULATION BECOMING ELONGATED FROM NORTHWEST TO SOUTHEAST.  IN
ADDITION...THE ASSOCIATED DEEP CONVECTION IS FARTHER AWAY FROM THE
CENTER.  AN ASCAT PASS FROM 2310 UTC SUGGESTED MAXIMUM WINDS OF
30-35 KT...AND GIVEN THE DECREASING DVORAK ESTIMATES AND THE RECENT
SATELLITE TRENDS...30 KT IS CHOSEN AS THE INTITAL INTENSITY.
SOUTHWESTERLY SHEAR...DRY AIR...AND MARGINAL SEA SURFACE
TEMPERATURES SHOULD CAUSE ERIN TO BECOME A REMNANT LOW WITHIN
48 HOURS.  THE LATEST NHC INTENSITY FORECAST FOLLOWS THE TREND OF
THE PREVIOUS ADVISORY AND IS SIMILAR TO THE GLOBAL MODEL
GUIDANCE...WHICH SHOW ERIN DEGENERATING INTO A TROUGH OF LOW
PRESSURE BY 72 HOURS.

ASCAT DATA SUGGEST THE CENTER OF ERIN HAS MOVED WESTWARD DURING THE
PAST FEW HOURS BUT A LONGER-TERM MOTION IS 290/10.  A SUBTROPICAL
RIDGE REBUILDING OVER THE CENTRAL ATLANTIC APPEARS TO HAVE CAUSED
THE LEFTWARD TURN AND SHOULD STEER ERIN ON THIS GENERAL COURSE FOR
THE NEXT COUPLE OF DAYS.  MODEL GUIDANCE HAS SHIFTED NOTABLY
SOUTHWARD ON THIS CYCLE...WITH A FEW MODELS EVEN SHOWING A DUE
WESTWARD TRACK.  ASSUMING A WEAKER ERIN WOULD BECOME MORE STEERED
BY A STRONGER LOW-LEVEL RIDGE...THE NHC FORECAST IS ADJUSTED TO THE
SOUTH.


FORECAST POSITIONS AND MAX WINDS

INIT  18/0300Z 20.7N  37.7W   30 KT  35 MPH
 12H  18/1200Z 21.3N  39.2W   30 KT  35 MPH
 24H  19/0000Z 21.9N  41.3W   30 KT  35 MPH
 36H  19/1200Z 22.5N  43.6W   25 KT  30 MPH
 48H  20/0000Z 23.0N  46.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  21/0000Z...DISSIPATED

$$
FORECASTER BLAKE


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