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Tropical Storm NATE


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TROPICAL STORM NATE DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
1000 AM CDT THU SEP 08 2011
 
EARLY MORNING VISIBLE SATELLITE IMAGES SHOW A MORE ORGANIZED
TROPICAL CYCLONE THAN WAS SEEN LATE YESTERDAY AFTERNOON.  NATE HAS
THE APPEARANCE OF A SHEARED TROPICAL CYCLONE WITH THE CENTER
LOCATED NEAR THE NORTHEASTERN TIP OF THE MAIN CONVECTIVE MASS. THE
INITIAL WIND SPEED IS RAISED TO 45 KT...BASED ON A SHIP OBSERVATION
OF 40 KT TO THE SOUTHEAST OF THE CENTER...AND RECENT STRONGER WIND
REPORTS FROM ELEVATED PEMEX OIL RIGS IN THE BAY OF CAMPECHE.  AN
AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO
INVESTIGATE NATE THIS AFTERNOON AND SHOULD PROVIDE A BETTER
ASSESSMENT OF THE INTENSITY.
 
NATE HAS NOT MOVED MUCH OVERNIGHT OR THIS MORNING...ALTHOUGH THE
LATEST SATELLITE AND MICROWAVE IMAGERY SUGGESTS THAT THE CENTER IS
A LITTLE SOUTH OF THE EARLIER ESTIMATES. THE CYCLONE IS FORECAST TO
REMAIN IN A WEAK STEERING PATTERN BETWEEN MID-LEVEL RIDGES OVER
MEXICO AND THE NORTHERN CARIBBEAN DURING THE NEXT 12-24 HOURS. IN A
DAY OR SO...NATE IS EXPECTED TO MOVE SLOWLY NORTHWARD AROUND THE
WESTERN PERIPHERY OF THE CARIBBEAN RIDGE. AFTER 36-48 HOURS...THE
MODEL SPREAD BECOMES INCREASINGLY LARGE...AS SUBTLE DIFFERENCES IN
THE STRENGTH AND ORIENTATION OF A MID/UPPER-LEVEL LOW AND TROUGH
EXTENDING FROM THE OHIO VALLEY SOUTHWESTWARD HAVE SIGNIFICANT
IMPLICATIONS ON THE FUTURE TRACK OF THE CYCLONE. THE LATEST GFS AND
GFDL MODELS...WHICH SHOW A SLIGHTLY DEEPER TROUGH...MOVE NATE
NORTHWARD TOWARD THE NORTHERN GULF COAST. THE ECMWF AND NOGAPS
MODELS DEPICT A WEAKER TROUGH THAT DOES NOT CAPTURE NATE AND ALLOWS
IT TURN TURN WESTWARD TOWARD MEXICO TO THE SOUTH OF A BUILDING
RIDGE...ALTHOUGH IT SHOULD BE NOTED THAT THERE IS CONSIDERABLE
SPREAD AMONG THE ECMWF ENSEMBLE MEMBERS. THE OFFICIAL FORECAST HAS
BEEN SHIFTED TO THE RIGHT AND LIES BETWEEN THESE TWO VIABLE
SCENARIOS BUT HAS NOT BEEN SHIFTED AS FAR AS THE TVCA CONSENSUS.
THE NOAA G-IV AIRCRAFT IS SCHEDULED TO PERFORM A SYNOPTIC
SURVEILLANCE MISSION LATER TODAY...WHICH WILL HOPEFULLY HELP REDUCE
THE SPREAD IN THE TRACK GUIDANCE TONIGHT.
 
NATE IS CURRENTLY LOCATED IN AN ENVIRONMENT OF LIGHT TO MODERATE
NORTHEASTERLY SHEAR.  THE SHEAR IS FORECAST TO LESSEN DURING THE
NEXT DAY OR SO...WHICH SHOULD ALLOW FOR GRADUAL STRENGTHENING.
LATER IN THE FORECAST PERIOD...SOUTHWESTERLY SHEAR IS EXPECTED TO
INCREASE AND ALONG WITH DRIER LOW- TO MID-LEVEL AIR...IS FORECAST TO
SLOW THE INTENSIFICATION PROCESS. THE UPDATED INTENSITY FORECAST IS
SIMILAR TO THE PREVIOUS ADVISORY AND IS IN GOOD AGREEMENT WITH THE
SHIPS/LGEM GUIDANCE.

 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/1500Z 20.0N  92.4W   45 KT  50 MPH
 12H  09/0000Z 20.4N  92.2W   55 KT  65 MPH
 24H  09/1200Z 21.0N  92.2W   55 KT  65 MPH
 36H  10/0000Z 21.8N  92.7W   60 KT  70 MPH
 48H  10/1200Z 22.5N  93.2W   65 KT  75 MPH
 72H  11/1200Z 23.1N  93.8W   70 KT  80 MPH
 96H  12/1200Z 23.6N  94.4W   70 KT  80 MPH
120H  13/1200Z 24.0N  95.0W   70 KT  80 MPH
 
$$
FORECASTER BROWN
 
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