Tropical Storm NORBERT Forecast Discussion

000
WTPZ45 KNHC 061445
TCDEP5
TROPICAL STORM NORBERT DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP152008
800 AM PDT MON OCT 06 2008

DVORAK INTENSITY ESTIMATES FROM 1200 UTC SUPPORT AN INITIAL
INTENSITY OF 55 KT FOR THIS ADVISORY BUT THE LAST FEW SATELLITE
IMAGES SUGGEST THAT THE CYCLONE IS BECOMING BETTER ORGANIZED. 
NORBERT IS EXPECTED TO BE WITHIN A FAVORABLE ENVIRONMENT FOR
STRENGTHENING AND THE OFFICIAL FORECAST CALLS FOR THE CYCLONE TO
BECOME A HURRICANE DURING THE NEXT 12-24 HOURS.  THE HWRF MODEL
REMAINS SOMEWHAT OF AN OUTLIER AND SHOWS NORBERT REACHING MAJOR
HURRICANE STRENGTH.  THE OFFICIAL FORECAST IS MORE CONSERVATIVE AND
IS IN BEST AGREEMENT WITH THE GFDL SOLUTION.  BY DAYS 4 AND
5...NORBERT IS FORECAST TO BE APPROACHING COOLER WATERS AND A MORE
STABLE AIR MASS.  THEREFORE...SOME WEAKENING IS SHOWN AT THE
EXTENDED TIME RANGES.  HOWEVER...THE ULTIMATE ENVIRONMENT IN WHICH
NORBERT WILL BE LOCATED AT DAYS 4 AND 5 IS STRONGLY DEPENDENT ON
THE TRACK FORECAST...AND NORBERT COULD ENCOUNTER LESS FAVORABLE
CONDITIONS SOONER OR LATER THAN SHOWN HERE.  

NORBERT CONTINUES TO BE STEERED BY A MID-LEVEL RIDGE TO THE NORTH
AND IS MOVING WESTWARD OR 280/7. THIS GENERAL MOTION IS EXPECTED TO
CONTINUE FOR THE NEXT 2 DAYS AS THE RIDGE REMAINS TO THE NORTH OF
THE CYCLONE.  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 WITH THE
GFS MODEL NEVER GETTING NORBERT FAR ENOUGH NORTH TO RESPOND TO THE
AFOREMENTIONED TROUGH AND THE ECMWF SHOWING THE TROUGH BYPASSING
NORBERT AND LEAVING IT BEHIND.   WHILE THESE SOLUTIONS CANNOT BE
COMPLETELY IGNORED...THE OFFICIAL FORECAST FOLLOWS THE REMAINING
TRACK MODELS BY SHOWING A NORTHWARD AND NORTH-NORTHEASTWARD TURN AT
DAYS 4 AND 5...RESPECTIVELY.  HOWEVER...THE FORWARD SPEED SHOWN IN
THE OFFICIAL FORECAST IS SLOWER THAN FORECAST BY THOSE MODELS. THIS
RESULTS IN ONLY A SMALL SOUTHWARD SHIFT TO THE PREVIOUS OFFICIAL
FORECAST. 

FORECAST POSITIONS AND MAX WINDS

INITIAL      06/1500Z 14.3N 104.7W    55 KT
 12HR VT     07/0000Z 14.5N 105.6W    65 KT
 24HR VT     07/1200Z 14.9N 106.9W    70 KT
 36HR VT     08/0000Z 15.4N 108.2W    75 KT
 48HR VT     08/1200Z 16.2N 109.6W    80 KT
 72HR VT     09/1200Z 18.0N 112.0W    80 KT
 96HR VT     10/1200Z 20.5N 113.0W    75 KT
120HR VT     11/1200Z 23.5N 112.5W    60 KT

$$
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