ZCZC MIATCDAT5 ALL TTAA00 KNHC DDHHMM 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 NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:44:01 UTC