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Tropical Storm NORMAN

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TROPICAL STORM NORMAN DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP152006
800 AM PDT TUE OCT 10 2006
 
SHORTWAVE INFRARED IMAGERY AND AN EARLIER TRMM OVERPASS DEPICTED
THAT THE CIRCULATION CENTER HAS BECOME LESS DEFINED AND FARTHER
SEPARATED TO THE SOUTHWEST FROM THE DEEP CONVECTION.  THE UW-CIMSS
WIND SHEAR PRODUCT INDICATES 10 TO 20 KT OF SOUTHWESTERLY SHEAR
OVER THE TROPICAL CYCLONE.  BECAUSE OF THE CURRENT SHEARED
STRUCTURE OF THE SYSTEM AND DIFFICULTY LOCATING THE CENTER...THE
SATELLITE INTENSITY FIXES HAVE BECOME WIDELY DISPERSED AND ARE
RANGING FROM 30 TO 45 KT.  THE INITIAL INTENSITY IS DECREASED TO 40
KT BASED ON A BLEND OF THE CLASSIFICATIONS.

LARGE SCALE MODELS AS WELL AS THE SHIPS AND THE GFDL ALL SUGGEST A
STEADY WEAKENING THROUGH THE ENTIRE FORECAST IN RESPONSE TO
INCREASING VERTICAL SHEAR.  THE OFFICIAL INTENSITY FORECAST IS
ADJUSTED SLIGHTLY DOWNWARD FROM THE PREVIOUS FORECAST AND IS CLOSE
TO THE SHIPS/GFDL GUIDANCE.
 
INITIAL MOTION IS 360/3...WITHIN THE WESTERN PERIPHERY OF A
WEAKENING MID-TROPOSPHERIC RIDGE EXTENDING WESTWARD FROM CENTRAL
MEXICO.  THE DYNAMICAL MODELS ALL INDICATE THAT NORMAN WILL BEGIN A
TURN TO THE NORTHEAST WITHIN THE NEXT 24 HOURS AS A DEEP LAYER
TROUGH EXTENDING FROM THE SOUTHWESTERN U.S. DIGS SOUTHWARD OFF OF
THE BAJA PENINSULA.  THROUGH THE REMAINDER OF THE FORECAST...THE
UKMET...ECMWF AND THE NOGAPS INDICATE A DRIFT INCREASINGLY EASTWARD
WITHIN THE LOW-LEVEL WESTERLIES OF A RIDGE TO THE SOUTH.  ON THE
OTHER HAND...THE GFS...GFDL AND THE FSU SUPERENSEMBLE REFLECT A
CONTINUED NORTHEASTWARD MOTION INFLUENCED BY THE STEERING FLOW OF
THE DEEPENING TROUGH WEST OF THE BAJA PENINSULA AND A MID-LEVEL
RIDGE EXTENDING SOUTHWESTWARD FROM SOUTHERN MEXICO.  THE OFFICIAL
FORECAST IS SLIGHTLY SLOWER THAN THE PREVIOUS PACKAGE BEYOND 48
HOURS AND IS BASED ON A CONSENSUS OF ALL THE MODELS WITH EMPHASIS
ON THE UKMET CLUSTER...INDICATING A VERTICALLY SHALLOW TROPICAL
CYCLONE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/1500Z 17.0N 117.9W    40 KT
 12HR VT     11/0000Z 17.8N 117.5W    35 KT
 24HR VT     11/1200Z 18.7N 116.6W    35 KT
 36HR VT     12/0000Z 19.5N 115.6W    30 KT
 48HR VT     12/1200Z 20.0N 114.7W    30 KT
 72HR VT     13/1200Z 21.0N 113.0W    25 KT...DISSIPATING
 96HR VT     14/1200Z 22.0N 111.5W    20 KT...REMNANT LOW
120HR VT     15/1200Z...DISSIPATED
 
$$
FORECASTER ROBERTS/FRANKLIN
 
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