142 
 WTNT44 KNHC 272055
 TCDAT4
  
 TROPICAL STORM DON DISCUSSION NUMBER   1
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042011
 400 PM CDT WED JUL 27 2011
  
 AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING THE
 TROPICAL WAVE OVER THE SOUTHERN GULF OF MEXICO FOUND A CLOSED
 SURFACE CIRCULATION WITH A CENTRAL PRESSURE OF 1001 MB.  THE
 MAXIMUM 1000 FT FLIGHT-LEVEL WINDS WERE 45 KT EAST OF THE CENTER...
 AND THERE WERE SEVERAL RELIABLE-LOOKING SMFR SURFACE WIND ESTIMATES
 OF 35 KT.  BASED ON THIS...THE SYSTEM IS DESIGNATED AS TROPICAL
 STORM DON.  THE AIRCRAFT DATA SHOW THAT THE CIRCULATION CENTER IS
 ELONGATED...AND IT IS POSSIBLE SOME REFORMATION OF THE CENTER COULD
 OCCUR TONIGHT IN RESPONSE TO CONVECTIVE BURSTS.
 
 THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 295/10.  DON IS SOUTH OF
 A LOW/MID-LEVEL RIDGE OVER THE NORTHERN GULF OF MEXICO...AND WATER
 VAPOR IMAGERY SHOWS UPPER-LEVEL EASTERLY FLOW DEVELOPING TO THE
 NORTH AND NORTHEAST OF THE STORM.  THE LARGE-SCALE MODELS FORECAST
 THAT WITHIN 24 HR DON WILL BECOME EMBEDDED IN DEEP-LAYER EASTERLY
 TO SOUTHEASTERLY FLOW THAT SHOULD PERSIST FOR SEVERAL DAYS.  THIS
 EVOLUTION SHOULD STEER THE STORM GENERALLY NORTHWESTWARD.  WHILE
 THE MODELS AGREE WITH THIS SCENARIO...THERE IS A SPREAD IN THE
 GUIDANCE ON WHERE DON WILL REACH THE NORTHWESTERN GULF COAST.  THE
 GFDL AND GFS ARE FARTHEST TO THE RIGHT...CLOSER TO THE HOUSTON/
 GALVESTON AREA.  THE UKMET/ECMWF ARE FARTHEST TO THE LEFT...CLOSER
 TO THE BROWNSVILLE AREA.  THE FORECAST TRACK LIES BETWEEN THESE
 EXTREMES AND IS CLOSE TO THE VARIOUS CONSENSUS MODELS.
  
 DON IS OVER THE WARM WATERS OF THE GULF OF MEXICO...AND THE
 GLOBAL MODELS FOR THE MOST PART FORECAST LIGHT TO MODERATE
 VERTICAL WIND SHEAR OVER THE SYSTEM FOR THE NEXT 72 HR.  DESPITE
 THIS...NONE OF THOSE MODELS SUGGEST SIGNIFICANT STRENGTHENING OF
 THE STORM...AND NEITHER DOES THE GFDL.  THE SHIPS...LGEM...AND HWRF
 MODELS FORECAST THE SYSTEM TO REACH 55-65 KT BEFORE LANDFALL IN
 TEXAS...AND THE INTENSITY FORECAST FOLLOWS THAT SCENARIO IN BEST
 AGREEMENT WITH THE SHIPS MODEL.  IT SHOULD BE NOTED THAT THE 48 HR
 INTENSITY OF 55 KT IS WELL BEFORE LANDFALL...AND DON COULD GET
 STRONGER THAN THIS BETWEEN 48-72 HR.
  
 WATCHES AND/OR WARNINGS WILL LIKELY BE REQUIRED FOR PORTIONS OF THE
 TEXAS COAST TONIGHT OR THURSDAY.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  27/2100Z 22.2N  87.0W   35 KT  40 MPH
  12H  28/0600Z 23.1N  88.7W   40 KT  45 MPH
  24H  28/1800Z 24.5N  90.9W   45 KT  50 MPH
  36H  29/0600Z 25.8N  92.8W   50 KT  60 MPH
  48H  29/1800Z 27.1N  94.8W   55 KT  65 MPH
  72H  30/1800Z 29.0N  99.5W   35 KT  40 MPH...INLAND
  96H  31/1800Z 31.0N 103.0W   25 KT  30 MPH...INLAND
 120H  01/1800Z...DISSIPATED
  
 $$
 FORECASTER BEVEN
  
 

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