Tropical Storm NATE

ZCZC MIATCDAT5 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM NATE DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
400 AM CDT THU SEP 08 2011
 
NATE APPEARS TO BE SLOWLY BECOMING BETTER ORGANIZED. A CURVED BAND 
NOW WRAPS AROUND THE NORTHWEST SEMICIRCLE. HOWEVER...CONVENTIONAL
AND MICROWAVE SATELLITE IMAGERY THAT THE MAIN CONVECTIVE MASS IS
CONFINED TO THE SOUTHWEST QUADRANT...WITH THE LOW-LEVEL CENTER
STILL DISPLACED ABOUT 60 N MI NORTHEAST OF IT. DVORAK
T-NUMBERS FROM TAFB AND SAB HAVE INCREASED SOME SINCE
0000 UTC BUT REMAIN BELOW TROPICAL STORM STRENGTH. A SHIP LOCATED
ABOUT 50 N MI SOUTHEAST OF THE CENTER REPORTED 45 KT WIND AT 0300
UTC...BUT THIS OBSERVATION WAS JUDGED TO BE A BIT HIGH. BASED UPON
THESE DATA...THE INITIAL INTENSITY ESTIMATE IS HELD AT 40 KT.
 
THE CENTER OF NATE APPEARS TO HAVE NOT MOVED MUCH RECENTLY.
HOWEVER...SINCE THE CENTER REMAINS HARD TO LOCATE...THE INITIAL
MOTION ESTIMATE OF 090/02 REMAINS AS UNCERTAIN AS IT WAS EARLIER.
THE CYCLONE REMAINS IN A WEAK STEERING FLOW IN BETWEEN MID-LEVEL
RIDGES OVER THE NORTHERN CARIBBEAN AND MEXICO...WITH SHOULD ONLY
ALLOW A SLOW AND ERRATIC MOTION FOR THE NEXT DAY OR SO. AFTER
THAT...A SLOW NORTHWESTWARD TO NORTHWESTWARD MOTION SHOULD COMMENCE
UNTIL ABOUT 72 HOURS AS THE MID-LEVEL RIDGE TO THE EAST OF NATE
LIFTS NORTHWARD.  LATER IN THE FORECAST PERIOD...GLOBAL MODELS SHOW
THE MEXICAN RIDGE BUILDING EASTWARD AND INDUCING A GENERALLY
WESTWARD TRACK.  WHILE THERE CONTINUES TO BE A FAIR AMOUNT OF
NORTH-TO-SOUTH SPREAD IN THE TRACK GUIDANCE THIS CYCLE....THE MORE
RELIABLE GFS/ECWMF REMAIN THE MOST CONSISTENT. ONLY MINOR CHANGES
WERE MADE TO THE PREVIOUS TRACK FORECAST...WITH THE NEW TRACK IN
BEST AGREEMENT WITH THE GFS/ECMWF SOLUTIONS.
  
THE INTENSITY FORECAST FOR NATE IS CHALLENGING.  WHILE THE CYCLONE
IS LOCATED IN A DIFFLUENT UPPER-LEVEL WIND ENVIRONMENT...WATER VAPOR
IMAGERY SHOWS A TONGUE OF EXCEPTIONALLY DRY AIR NEAR AND NORTH OF
NATE. THIS...AND THE RELATIVE LACK OF CONVECTIVE ORGANIZATION...
WOULD ARGUE AGAINST ANY SIGNIFICANT INTENSIFICATION IN THE SHORT
TERM.  LATER IN THE FORECAST PERIOD...SHIPS GUIDANCE STILL
INDICATES THE PRESENCE OF A RELATIVELY DRY LOW- TO MID-LEVEL AIR
MASS AND A SUDDEN INCREASE IN SOUTHWESTERLY SHEAR ASSOCIATED WITH A
TROUGH OVER THE SOUTHEASTERN UNITED STATES.  THIS SUGGESTS THAT THE
STRONGER DYNAMICAL GUIDANCE...E.G. HWRF...MAY BE IN DOUBT. THE
OFFICIAL NHC OFFICIAL IS SIMILAR TO THE PREVIOUS ONE AND PUTS MORE
WEIGHT ON THE STATISTICAL INTENSITY MODEL OUTPUT. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0900Z 20.4N  92.4W   40 KT  45 MPH
 12H  08/1800Z 20.4N  92.2W   45 KT  50 MPH
 24H  09/0600Z 20.6N  92.2W   50 KT  60 MPH
 36H  09/1800Z 21.2N  92.5W   55 KT  65 MPH
 48H  10/0600Z 21.8N  93.0W   60 KT  70 MPH
 72H  11/0600Z 22.7N  94.2W   65 KT  75 MPH
 96H  12/0600Z 23.0N  95.5W   70 KT  80 MPH
120H  13/0600Z 23.0N  97.0W   70 KT  80 MPH
 
$$
FORECASTER KIMBERLAIN/PASCH
 
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