000
WTNT45 KNHC 100846
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
400 AM CDT SAT SEP 10 2011
 
AN AIR FORCE RECONNAISSANCE PLANE INVESTIGATING NATE THIS MORNING
FOUND A MAXIMUM FLIGHT-LEVEL WIND OF 49 KT AND SURFACE WINDS NEAR
40 KT. DROPSONDE DATA ALSO SUGGEST THAT THE MINIMUM PRESSURE IS UP
A LITTLE TO 1000 MB. THESE DATA SUGGEST THAT NATE MAY HAVE WEAKENED
SLIGHTLY...BUT SINCE THE PLANE WAS UNABLE TO SAMPLE THE
SOUTHEASTERN SIDE OF THE TROPICAL STORM...I PREFER TO HOLD THE
INITIAL WIND SPEED AT 45 KT.   
 
SATELLITE AND AIRCRAFT FIXES SUGGEST THAT NATE IS NOW ON A MORE
STEADY WESTWARD PATH...WITH THE LATEST INITIAL MOTION ESTIMATE OF
270/4.  A BUILDING LOW- TO MID-LEVEL RIDGE TO THE NORTH OF THE STORM
SHOULD STEER NATE WESTWARD OR WEST-SOUTHWESTWARD WITH A SLIGHT
INCREASE IN FORWARD SPEED THROUGH LANDFALL OVER SOUTHERN
MEXICO...WHICH IS NOW FORECAST TO OCCUR IN ABOUT 36 HOURS. THE
OFFICIAL TRACK FORECAST IS FASTER AND A LITTLE TO THE SOUTH OF THE
PREVIOUS ONE...AND IS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.
 
AS MENTIONED IN THE PREVIOUS ADVISORY...THE WEAKENING OR LACK OF
STRENGTHENING OF NATE DURING THE PAST 24 HOURS...DESPITE A VERY
FAVORABLE ENVIRONMENT...WAS NOT WELL FORECAST BY THE NHC OR THE
MODELS.  THIS COULD BE THE RESULT OF COOL WATER UPWELLING DUE TO
THE VERY SLOW MOTION OF THIS TROPICAL CYCLONE.  NOW THAT NATE
APPEARS TO BE MOVING AND REMAINS IN A FAVORABLE ENVIRONMENT FOR
STRENGTHENING...SOME INTENSIFICATION APPEARS LIKELY.  THE OFFICIAL
FORECAST SHOWS STEADY STRENGTHENING UNTIL LANDFALL AND IS CLOSE TO
THE SHIPS MODEL.  NATE IS FORECAST TO DISSIPATE OVER THE SIERRA
MADRE MOUNTAINS BY 72 HOURS.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0900Z 20.0N  93.7W   45 KT  50 MPH
 12H  10/1800Z 20.0N  94.3W   50 KT  60 MPH
 24H  11/0600Z 19.9N  95.4W   55 KT  65 MPH
 36H  11/1800Z 19.8N  96.6W   60 KT  70 MPH...INLAND
 48H  12/0600Z 19.7N  97.7W   30 KT  35 MPH...INLAND
 72H  13/0600Z...DISSIPATED
 
$$
FORECASTER CANGIALOSI/AVILA