Tropical Storm NATE

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TROPICAL STORM NATE DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
400 AM CDT FRI SEP 09 2011
 
NATE HAS SEEMINGLY WEAKENED A LITTLE OVERNIGHT. DEEP CONVECTION HAS
DIMINISHED SIGNIFICANTLY OVER THE PAST 6-12 HOURS...ALTHOUGH THERE
HAS BEEN A MODEST COMEBACK OVER THE LAST HOUR OR TWO. THE HIGHEST
SFMR WINDS REPORTED FROM THE AIRCRAFT INVESTIGATING NATE AROUND 06Z
WERE 47 KT IN THE SOUTHEAST QUADRANT...AN AREA WHERE 60 KT SFMR
WINDS WERE FOUND YESTERDAY AFTERNOON. THE MINIMUM PRESSURE WAS ALSO
UP...TO 998 MB. BASED ON THESE DATA...THE ESTIMATED INTENSITY IS
LOWERED TO 55 KT. AN ASCAT PASS ALSO SUGGESTS THE WIND RADII HAVE
CONTRACTED.
 
RADAR AND RECONNAISSANCE DATA INDICATE THAT NATE IS STILL
ESSENTIALLY STATIONARY...AND THE GUIDANCE IS COMING INTO STRONGER
AGREEMENT THAT NATE WILL NOT BE ABLE TO MAKE MUCH NORTHWARD
PROGRESS.  BOTH THE GFS AND ECMWF SHOW A NARROW RIDGE DEVELOPING TO
THE NORTH OF THE CYCLONE THAT IS EXPECTED TO TURN NATE WESTWARD
OVER THE NEXT TWO TO THREE DAYS.  IN FACT...THERE IS A FAIR AMOUNT
OF GUIDANCE NOW THAT TAKES NATE WESTWARD AND THEN SOUTHWESTWARD
ACROSS THE BAY OF CAMPECHE.  THE SOUTHERNMOST MODEL IS THE HFIP
COAMPS-TC...WHILE THE NORTHERN EDGE OF THE GUIDANCE ENVELOPE IS
DEFINED BY THE ECMWF AND UKMET.  THE PRESENT MODEL SUITE REQUIRES A
SOUTHWARD ADJUSTMENT IN THE OFFICIAL FORECAST...WHICH IS IN GOOD
AGREEMENT WITH THE ECMWF BUT STILL NORTH OF THE CONSENSUS MODELS.
 
ALTHOUGH NATE HAS WEAKENED A LITTLE...THE ENVIRONMENT IS STILL
EXPECTED TO BE FAVORABLE FOR STRENGTHENING OVER THE NEXT
TWO TO THREE DAYS. THE GFS AND ECMWF BOTH SHOW A DIFLUENT AND
ANTICYCLONIC FLOW ALOFT...AND ONCE NATE BEGINS TO MOVE IT WILL HAVE
A DEEPER RESERVOIR OF VERY WARM WATER UNDERNEATH. THE DRY AIR IN
THE WESTERN GULF APPEARS TO BE THE PRIMARY INHIBITING FACTOR. THE
OFFICIAL FORECAST IS NEAR THE UPPER END OF THE TRADITIONAL
GUIDANCE...CLOSE TO THE LGEM STATISTICAL MODEL...THE HWRF...AND
GFDL. AMONG THE HFIP MODELS...WHICH AS A GROUP PERFORMED VERY WELL
DURING IRENE...THE UNIVERSITY OF WISCONSIN UWN8 IS MOST
AGRESSIVE...BRINGING NATE TO ABOUT 90 KT...WHILE THE COAMPS-TC AND
AHW ARE 15-25 KT LOWER.
 
A HURRICANE WATCH WILL LIKELY BE REQUIRED FOR A PORTION OF THE
WESTERN GULF COAST OF MEXICO LATER TODAY.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0900Z 19.9N  92.3W   55 KT  65 MPH
 12H  09/1800Z 20.3N  92.5W   60 KT  70 MPH
 24H  10/0600Z 20.7N  93.1W   65 KT  75 MPH
 36H  10/1800Z 20.8N  94.0W   75 KT  85 MPH
 48H  11/0600Z 20.9N  95.0W   85 KT 100 MPH
 72H  12/0600Z 20.5N  97.5W   80 KT  90 MPH...INLAND
 96H  13/0600Z 20.0N 100.5W   25 KT  30 MPH...INLAND
120H  14/0600Z...DISSIPATED
 
$$
FORECASTER FRANKLIN
 
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