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Tropical Storm NORBERT


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TROPICAL STORM NORBERT DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP152008
200 PM PDT MON OCT 06 2008

SATELLITE IMAGERY SUGGEST THAT NORBERT CONTINUES TO GRADUALLY BECOME
BETTER ORGANIZED...AND BOTH OBJECTIVE AND SUBJECTIVE DVORAK
INTENSITY ESTIMATES HAVE INCREASED SINCE THIS MORNING.  THE
OFFICIAL FORECAST IS INCREASED TO 60 KT AND NORBERT IS
NEARING HURRICANE STRENGTH.  THE INTENSITY FORECAST AND THE
ASSOCIATED REASONING ARE UNCHANGED FROM THE EARLIER PACKAGE. 
NORBERT IS EXPECTED TO BE WITHIN A FAVORABLE ENVIRONMENT FOR
STRENGTHENING AND ALL OF THE AVAILABLE GUIDANCE CALLS FOR THE
CYCLONE TO REACH AT LEAST CATEGORY ONE INTENSITY IN A COUPLE OF
DAYS.  THE HWRF REMAINS SOMEWHAT OF AN OUTLIER...ALBEIT A LITTLE
WEAKER THAN BEFORE...AND SHOWS NORBERT BECOMING A MAJOR HURRICANE. 
THE REMAINING INTENSITY MODELS ARE LOWER...AND A CONSENSUS OF THESE
MODELS IS THE BASIS FOR THE OFFICIAL FORECAST.   BY DAYS 4 AND
5...NORBERT IS FORECAST TO BE APPROACHING COOLER WATERS AND A MORE
STABLE AIR MASS.  THEREFORE...SOME WEAKENING IS SHOWN BEYOND 72
HOURS.  HOWEVER...MUCH UNCERTAINTY REMAINS IN THE TRACK
FORECAST...ESPECIALLY IN TERMS OF FORWARD SPEED...AT THESE
EXTENDED RANGES AND NORBERT COULD REACH LESS FAVORABLE CONDITIONS
SOONER OR LATER THAN SHOWN HERE.  
 
NORBERT CONTINUES ON A GENERAL WESTWARD TO WEST-NORTHWESTWARD
HEADING OR 290/7. THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR
THE NEXT 2 DAYS AS A MID-LEVEL RIDGE REMAINS TO THE NORTH. 
THEREAFTER...A LARGE TROUGH IS FORECAST TO DIG SOUTHWARD ALONG THE
WEST COAST OF THE UNITED STATES WHICH SHOULD RESULT IN A NORTHWARD
TURN IN 3-4 DAYS.  THERE ARE STILL SOME DIFFERENCES AMONG THE
VARIOUS TRACK MODELS BEYOND 72 HOURS AND THE MODELS HAVE NOT
DEMONSTRATED GOOD RUN-TO-RUN CONSISTENCY.  THE GFS REMAINS THE
SOUTHERN OUTLIER AND NEVER GETS NORBERT FAR ENOUGH NORTH TO RESPOND
TO THE TROUGH.  CONVERSELY...THE UKMET AND NOGAPS SHOW NORBERT
ACCELERATING NORTH-NORTHEASTWARD AHEAD OF THE TROUGH.  THE OFFICIAL
FORECAST IS AGAIN SHIFTED A LITTLE SOUTH EARLY IN THE FORECAST
PERIOD AND WEST LATE IN THE FORECAST PERIOD.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/2100Z 14.5N 105.3W    60 KT
 12HR VT     07/0600Z 14.7N 106.3W    65 KT
 24HR VT     07/1800Z 15.1N 107.7W    70 KT
 36HR VT     08/0600Z 15.7N 109.0W    75 KT
 48HR VT     08/1800Z 16.5N 110.4W    80 KT
 72HR VT     09/1800Z 18.5N 112.5W    80 KT
 96HR VT     10/1800Z 21.0N 113.5W    75 KT
120HR VT     11/1800Z 24.0N 112.5W    60 KT
 
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