[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 300852
TCDAT4

TROPICAL STORM ISAAC DISCUSSION NUMBER  37
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
400 AM CDT THU AUG 30 2012

ISAAC IS SLOWLY WEAKENING AS MORE OF ITS LARGE CIRCULATION MOVES
OVER LAND.  BASED ON THE LATEST SURFACE WIND OBSERVATIONS NEAR THE
NORTHERN GULF COAST...THE MAXIMUM WINDS HAVE DIMINISHED TO NEAR 40
KT.  THESE WINDS ARE OCCURRING PRIMARILY OVER WATER OR ALONG THE
COASTLINE.   CONTINUED GRADUAL WEAKENING IS EXPECTED...AND ISAAC IS
LIKELY TO BECOME A TROPICAL DEPRESSION BY THIS EVENING.  THE
OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ONE...AND IS
MORE OR LESS IN AGREEMENT WITH THE STATISTICAL-DYNAMICAL GUIDANCE.

CENTER FIXES USING SURFACE SYNOPTIC DATA AND NATIONAL WEATHER
SERVICE DOPPLER RADAR IMAGERY INDICATE THAT ISAAC IS MOVING
NORTHWESTWARD AT A SLIGHTLY FASTER PACE...325/7.  THE TRACK
FORECAST AND PROGNOSTIC REASONING REMAIN ESSENTIALLY UNCHANGED.
OVER THE NEXT SEVERAL DAYS...THE PRIMARY STEERING MECHANISM SHOULD
BE THE FLOW BETWEEN THE MID-LATITUDE WESTERLIES AND A RIDGE OVER
THE SOUTHEASTERN UNITED STATES.  AS A RESULT THE CYCLONE IS
EXPECTED TO TURN NORTHWARD...NORTHEASTWARD...AND EASTWARD DURING
THE FORECAST PERIOD.  THE OFFICIAL TRACK FORECAST IS VERY CLOSE TO
THE PREVIOUS ONE...AND ALSO CLOSE TO THE LATEST DYNAMICAL MODEL
CONSENSUS.

HEAVY RAINFALL AND A SIGNIFICANT FLOOD THREAT ARE EXPECTED TO SPREAD
INLAND ACROSS PORTIONS OF THE CENTRAL UNITED STATES DURING THE NEXT
SEVERAL DAYS.  WATER LEVELS ALONG THE NORTHERN GULF COAST WILL
REMAIN ELEVATED THROUGH AT LEAST THIS MORNING.  TORNADOES REMAIN A
THREAT AS WELL FROM THIS SYSTEM TODAY.

FORECAST POSITIONS AND MAX WINDS

INIT  30/0900Z 30.9N  91.6W   40 KT  45 MPH
 12H  30/1800Z 31.9N  92.3W   35 KT  40 MPH...INLAND
 24H  31/0600Z 33.8N  93.2W   30 KT  35 MPH...INLAND
 36H  31/1800Z 36.0N  93.5W   25 KT  30 MPH...INLAND
 48H  01/0600Z 38.0N  93.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  02/0600Z 39.5N  90.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
 96H  03/0600Z 40.0N  86.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  04/0600Z 40.5N  82.0W   15 KT  15 MPH...POST-TROP/REMNT LOW

$$
FORECASTER PASCH


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