Tropical Storm NATE

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TROPICAL STORM NATE DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
1000 AM CDT FRI SEP 09 2011

EARLY MORNING VISIBLE IMAGERY SHOWS THAT NATE HAS A WELL-ORGANIZED
CLOUD PATTERN...HOWEVER DRY AIR OVER THE WESTERN SEMICIRCLE
CONTINUES TO SUPPRESS DEEP CONVECTION IN THAT PORTION OF THE
CIRCULATION AND THE INFRARED PRESENTATION REMAINS UNIMPRESSIVE. THE
INITIAL INTENSITY IS HELD AT 55 KT BASED ON A DVORAK CI-NUMBER OF
3.5 FROM TAFB AT 12Z. AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT WILL BE INVESTIGATING NATE LATER TODAY TO PROVIDE
INFORMATION ON THE STRUCTURE AND INTENSITY OF THE CYCLONE. 

THE ENVIRONMENT IN TERMS OF SSTS AND UPPER-LEVEL WINDS APPEARS
FAVORABLE FOR INTENSIFICATION. HOWEVER...ACCORDING THE SHIPS MODEL
OUTPUT...MID-LEVEL DRY AIR WILL REMAIN A LIMITING FACTOR. OVERALL
THE INTENSITY GUIDANCE HAS TRENDED A LITTLE LOWER THIS CYCLE...AND
THE OFFICIAL FORECAST HAS BEEN NUDGED DOWNWARD A BIT...BUT STILL
SHOWS NATE REACHING HURRICANE STRENGTH IN 24 HOURS. NOTE THAT SOME 
ADDITIONAL STRENGTHENING IS POSSIBLE BETWEEN THE 48-HOUR FORECAST
POINT AND LANDFALL...WHICH SHOULD OCCUR BY 72 HOURS. THE NHC
FORECAST IS CLOSE TO OR A BIT ABOVE THE LGEM MODEL THROUGH THE
PERIOD. 

BASED ON SATELLITE IMAGERY...NATE FINALLY APPEARS TO BE MOVING
SLOWLY NORTHWEST AT AROUND 3 KT AS THE RIDGE TO THE NORTH HAS
WEAKENED A LITTLE BIT. HOWEVER...THE MODEL GUIDANCE IS IN GOOD
AGREEMENT ON THE RIDGE RESTRENGTHENING NORTH OF NATE IN THE NEXT DAY
OR SO. BY 36 HOURS A TURN TOWARD THE WEST IS EXPECTED...WITH A
MOTION SOUTH OF DUE WEST POSSIBLE BEFORE LANDFALL. AFTER
LANDFALL...THE CYCLONE SHOULD WEAKEN QUICKLY AND DISSIPATE BEFORE
96 HOURS. HOWEVER A 96-HOUR POINT WAS INCLUDED TO SHOW THE SYSTEM
WEAKENING BELOW TROPICAL STORM INTENSITY BEFORE DISSIPATION. THE
NHC TRACK FORECAST IS AN UPDATE OF THE PREVIOUS ONE AND LIES
ROUGHLY BETWEEN THE GFS AND ECMWF IN TERMS OF HEADING AND FORWARD
SPEED. 
 
GIVEN THE FORECAST TIMING OF THE APPROACH OF TROPICAL STORM
CONDITIONS TO THE COAST...A HURRICANE WATCH IS REQUIRED FOR A
PORTION OF THE WESTERN GULF COAST OF MEXICO AT THIS TIME. 

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/1500Z 20.3N  92.6W   55 KT  65 MPH
 12H  10/0000Z 20.6N  93.0W   60 KT  70 MPH
 24H  10/1200Z 20.8N  93.8W   65 KT  75 MPH
 36H  11/0000Z 20.9N  94.8W   70 KT  80 MPH
 48H  11/1200Z 20.8N  95.9W   80 KT  90 MPH
 72H  12/1200Z 20.5N  98.5W   50 KT  60 MPH...INLAND
 96H  13/1200Z 20.0N 101.0W   25 KT  30 MPH...INLAND
120H  14/1200Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 
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