[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 161432
TCDAT5

TROPICAL DEPRESSION ERIN DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052013
1100 AM AST FRI AUG 16 2013

SATELLITE IMAGES INDICATE THAT ERIN HAS WEAKENED. THE STRUCTURE OF
THE CYCLONE CONSISTS OF A LOW-LEVEL CLOUD SWIRL WITH A COUPLE OF
SMALL AREAS OF CONVECTION SOUTH AND EAST OF THE CENTER. THE DVORAK
CLASSIFICATIONS HAVE FALLEN...AND ERIN IS DOWNGRADED TO A 30-KT
TROPICAL DEPRESSION FOR THIS ADVISORY. THE OBSERVED WEAKENING IS
LIKELY THE RESULT OF COOL SEA SURFACE TEMPERATURES AND STABLE AIR...
AS SEEN IN THE GOES-R PROVING GROUND AIRMASS PRODUCT. ALTHOUGH ERIN
IS EXPECTED TO MOVE OVER WARMER WATER IN A FEW DAYS...
SOUTHWESTERLY SHEAR IS ANTICIPATED TO INCREASE WHILE THE DEPRESSION
REMAINS IN A STABLE ATMOSPHERE. THE NHC INTENSITY PREDICTION CALLS
FOR LITTLE CHANGE IN STRENGTH THROUGHOUT THE FORECAST PERIOD. IT IS
POSSIBLE THAT ERIN COULD DEGENERATE TO A REMNANT LOW OR AN OPEN
TROUGH DURING THE NEXT FEW DAYS...AS SUGGESTED BY SOME OF THE MODEL
GUIDANCE.

THE DEPRESSION IS MOVING WEST-NORTHWESTWARD AT ABOUT 15 KT. THIS
GENERAL MOTION WITH SOME DECREASE IN FORWARD IS EXPECTED DURING THE
NEXT 36 HOURS WHILE THE CYCLONE FEELS SOME INFLUENCE FROM A
WEAKNESS IN THE SUBTROPICAL RIDGE. BETWEEN 36 AND 72 HOURS...LOW-
TO MID-LEVEL RIDGING IS FORECAST TO BECOME MORE PRONOUNCED TO THE
NORTH OF THE SYSTEM...CAUSING A TURN TOWARD THE WEST. BEYOND THAT
TIME...A GRADUAL TURN TO THE NORTHWEST IS PREDICTED WHEN THE WEAK
CYCLONE MOVES TOWARD ANOTHER WEAKNESS IN THE RIDGE. THE NHC TRACK
FORECAST IS VERY SIMILAR TO THE PREVIOUS ONE AND CLOSE TO THE
MULTI-MODEL CONSENSUS TVCA.

FORECAST POSITIONS AND MAX WINDS

INIT  16/1500Z 16.9N  32.1W   30 KT  35 MPH
 12H  17/0000Z 17.9N  34.0W   30 KT  35 MPH
 24H  17/1200Z 19.1N  36.2W   30 KT  35 MPH
 36H  18/0000Z 19.9N  38.2W   30 KT  35 MPH
 48H  18/1200Z 20.2N  40.2W   30 KT  35 MPH
 72H  19/1200Z 21.1N  44.6W   30 KT  35 MPH
 96H  20/1200Z 23.5N  49.5W   30 KT  35 MPH
120H  21/1200Z 25.5N  52.5W   30 KT  35 MPH

$$
FORECASTER CANGIALOSI



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