Tropical Storm NORBERT

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TROPICAL STORM NORBERT DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP152008
200 AM PDT SUN OCT 05 2008
 
THE OVERALL CLOUD PATTERN ASSOCIATED WITH NORBERT HAS GRADUALLY
IMPROVED DURING THE PAST FEW HOURS.  SATELLITE IMAGERY SHOWS THAT
CONVECTIVE BANDS HAVE DEVELOPED OVER THE SOUTH AND SOUTHEASTERN
PORTION OF THE STORM.  DVORAK INTENSITY ESTIMATES FROM TAFB AND 
SAB HAVE INCREASED TO 45 AND 35 KT...RESPECTIVELY.  THEREFORE...THE
INITIAL INTENSITY IS RAISED TO 40 KT.  THE CENTER POSITION HAS BEEN
ADJUSTED SLIGHTLY SOUTH OF THE EARLIER ESTIMATES BASED ON RECENT
MICROWAVE IMAGERY.   THE INITIAL MOTION ESTIMATE IS 270/6.  NORBERT
IS EXPECTED TO MOVE SLOWLY WEST TO WEST-NORTHWESTWARD DURING THE
NEXT SEVERAL DAYS...TO THE SOUTH OF A NARROW MID-LEVEL RIDGE.
LATE IN THE FORECAST PERIOD AS A TROUGH BEGINS TO DIG SOUTHWARD
ALONG THE WEST COAST OF THE UNITED STATES...THE RIDGE IS FORECAST
TO GRADUALLY WEAKEN.  THIS SHOULD ALLOW NORBERT TO TURN MORE TOWARD
THE NORTHWEST.  IN GENERAL...THE FORECAST GUIDANCE AGREES WITH THIS
SCENARIO...BUT AT VARYING SPEEDS.  THE HWRF AND UKMET ARE FASTER
AND MOVE NORBERT IN THE VICINITY OF THE SOUTHERN BAJA PENINSULA IN
4-5 DAYS...WHILE THE GFDL...ECMWF...AND NOGAPS ARE SOMEWHAT SLOWER. 
THE GFS CONTINUES TO BE MUCH SLOWER ON ITS WESTWARD PROGRESSION OF
THE STORM AS IT PREDICTS SOME INTERACTION BETWEEN NORBERT AND THE
DISTURBANCE TO THE EAST.  THE OFFICIAL FORECAST LEANS TOWARD THE
00Z ECMWF AND NOGAPS SOLUTIONS...BUT REMAINS A LITTLE SLOWER THAN
THE MODEL CONSENSUS.

SHEAR IS FORECAST TO BECOME LIGHT AS NORBERT REMAINS OVER SSTS
GREATER THAN 28C FOR THE NEXT SEVERAL DAYS.  THEREFORE...
STRENGTHENING IS EXPECTED AND THE OFFICIAL FORECAST FOLLOWS THE
GUIDANCE WHICH UNANIMOUSLY CALL FOR NORBERT TO REACH HURRICANE
STATUS IN ABOUT 36-48 HOURS.  THE NEW FORECAST IS CLOSEST TO THE
SHIPS AND LGEM GUIDANCE AND IS A LITTLE BELOW THE GFDL AND MUCH
MORE AGGRESSIVE HWRF MODEL.  IT SHOULD BE NOTED...THAT THERE IS
SOME POTENTIAL FOR RAPID INTENSIFICATION DURING THE NEXT DAY OR SO
AS THE SHIPS RI INDEX INDICATES THAT THE CHANCE OF A 30 KT OR
GREATER INCREASE IN INTENSITY IS ABOUT 3 TIMES THE SAMPLE MEAN.  
   
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/0900Z 14.2N 101.4W    40 KT
 12HR VT     05/1800Z 14.3N 102.3W    50 KT
 24HR VT     06/0600Z 14.6N 103.5W    60 KT
 36HR VT     06/1800Z 15.0N 104.7W    65 KT
 48HR VT     07/0600Z 15.4N 105.8W    70 KT
 72HR VT     08/0600Z 16.2N 108.0W    75 KT
 96HR VT     09/0600Z 17.5N 110.2W    75 KT
120HR VT     10/0600Z 19.5N 112.0W    75 KT
 
$$
FORECASTER BROWN
 
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