[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 170230
TCDAT5

TROPICAL STORM ERIN DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052013
1100 PM AST FRI AUG 16 2013

THUNDERSTORMS HAVE MARKEDLY INCREASED NEAR THE CENTER OF ERIN DURING
THE PAST FEW HOURS.  THE CENTER APPEARS TO BE ON THE SOUTHWESTERN
EDGE OF A LARGE COLD CLOUD SHIELD...WHICH IS CONSISTENT WITH A
SOUTHWESTERLY SHEAR ENVIRONMENT.  SHIP MGSG6 PASSED NEAR THE CENTER
RECENTLY AND REPORTED SUSTAINED WINDS OF 40 KT.  A REVIEW OF THE
HISTORY OF THE SHIP WIND DATA SUGGESTS THE REPORT IS PROBABLY A FEW
KNOTS TOO HIGH...BUT IT EASILY SUPPORTS A 35 KT INITIAL INTENSITY.
CONVECTION WILL LIKELY FLUCTUATE DURING THE NEXT DAY OR SO WHILE
ERIN MOVES OVER MARGINALLY WARM WATERS AND IN A MODERATE SHEAR
ENVIRONMENT.  WEAKENING SHOULD OCCUR BY 36H DUE TO AN INCREASE IN
SHEAR...WHICH WOULD PROMOTE THE MIXING OF VERY DRY AIR ALOFT INTO
THE CENTER OF THE CYCLONE.  ALTHOUGH THE SSTS NOTABLY INCREASE IN A
FEW DAYS...A COMBINATION OF THE DRY ENVIRONMENT...STRONG SHEAR AND
UPPER-LEVEL CONVERGENCE WILL PROBABLY CAUSE ERIN TO DEGENERATE INTO
A REMNANT LOW BY 96H.  THIS SOLUTION IS CONSISTENT WITH THE
RELIABLE GLOBAL MODELS...ALTHOUGH MOST OF THESE MODELS DISSIPATE
THE CYCLONE EVEN EARLIER THAN THE NEW NHC FORECAST.

ERIN APPEARS TO BE MOVING TO THE NORTHWEST AT ABOUT 14 KT...
ALTHOUGH THE CENTER IS HARDER TO LOCATE NOW DUE TO ALL OF THE
CONVECTION.  A GRADUAL TURN TOWARD THE WEST-NORTHWEST IS EXPECTED
AS ERIN ENCOUNTERS A REBUILDING SUBTROPICAL RIDGE.  THE CYCLONE
SHOULD 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 WEAKNESS IN THE RIDGE.
THE NEW NHC FORECAST IS VERY CLOSE TO THE PREVIOUS ONE THROUGH
36H...THEN IS SHIFTED WESTWARD NEAR A CONSENSUS OF THE UKMET...
GFS...ECMWF...AND FLORIDA STATE SUPERENSEMBLE GUIDANCE AFTER THAT
TIME.


FORECAST POSITIONS AND MAX WINDS

INIT  17/0300Z 18.5N  34.5W   35 KT  40 MPH
 12H  17/1200Z 19.5N  36.1W   35 KT  40 MPH
 24H  18/0000Z 20.2N  38.1W   35 KT  40 MPH
 36H  18/1200Z 20.7N  39.9W   30 KT  35 MPH
 48H  19/0000Z 21.0N  42.2W   30 KT  35 MPH
 72H  20/0000Z 22.0N  47.0W   30 KT  35 MPH
 96H  21/0000Z 24.5N  51.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  22/0000Z...DISSIPATED

$$
FORECASTER BLAKE



This weather bulletin was brought to you by:
www.nashvilleweather.net