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Tropical Storm NORMAN

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TROPICAL STORM NORMAN DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP152006
200 AM PDT TUE OCT 10 2006
 
NORMAN HAS SUSTAINED SOME DEEP CONVECTION OVER THE LAST SEVERAL
HOURS...ALTHOUGH THE COVERAGE HAS BEEN GENERALLY ON THE DECREASE. 
SHORTWAVE IR IMAGERY AND AN SSMI OVERPASS AT 0400 UTC SUGGEST THE
CYCLONE IS BEGINNING TO FEEL THE EFFECTS OF SOUTHWESTERLY SHEAR
OVER THE NORTHERN SEMICIRCLE...WITH THE CONVECTION BEGINNING TO
BECOME DISPLACED SLIGHTLY NORTH-NORTHEAST OF THE LOW-LEVEL CENTER.
THE ADVISORY INTENSITY IS HELD AT 45 KT BASED ON DVORAK ESTIMATES
OF 55 KT AND 45 KT FROM TAFB AND SAB...BUT LEANING TOWARD THE LOWER
ESTIMATE BASED ON A QUIKSCAT PASS AT 0230 UTC THAT DID NOT REVEAL
ANY WINDS GREATER THAN 45 KT. THE SHIPS MODEL SUGGESTS THAT BEYOND
ABOUT 12 HOURS THE SHEAR WILL STEADILY INCREASE THROUGH THE END OF
THE FORECAST PERIOD.  NORMAN WILL ALSO PASS OVER SLIGHTLY COOLER
SSTS BEYOND 12 HOURS. THE OFFICIAL FORECAST CONTINUES TO REFLECT
THESE UNFAVORABLE ENVIRONMENTAL FACTORS AND ANTICIPATES WEAKENING
BEYOND 24 HOURS. THE INTENSITY FORECAST IS A BLEND OF THE SHIPS AND
GFDL GUIDANCE...AND FOLLOWS THE FSU SUPERENSEMBLE CLOSELY.

NORMAN IS CURRENTLY MOVING VERY SLOWLY TO THE NORTH...TEMPORARILY
WITHIN A WEAKNESS IN THE STEERING FLOW...IN BETWEEN THE FAR WESTERN
PERIPHERY OF A WEAK MID-LEVEL RIDGE JUST OFF THE COAST OF CENTRAL
MEXICO...AND SOUTH OF THE DEEP-LAYER TROUGH EXTENDING FROM
CALIFORNIA SOUTHWARD OVER BAJA.  A QUIKSCAT AMBIGUITY ANALYSIS AND
THE SSMI OVERPASS AT 0400 UTC HELPED VERIFY THAT NORMAN HAS BEEN
MOVING SLIGHTLY SLOWER THAN PREVIOUSLY INDICATED...AND THE INITIAL
MOTION ESTIMATE IS ONLY 360/2.  HOWEVER...ALL OF THE TRACK MODEL
GUIDANCE SUGGESTS THIS SLOWDOWN IS TEMPORARY AND FORECAST A GRADUAL
TURN TOWARD THE NORTHEAST DURING THE NEXT DAY OR TWO. 
HOWEVER...THE MODELS GREATLY DISAGREE ON HOW FAR NORTH NORMAN WILL
TRAVEL AND HOW FAST.  THE NEW OFFICIAL FORECAST IS SLOWER THAN THE
PREVIOUS ADVISORY TO COME INTO BETTER AGREEMENT WITH MOST OF THE
GUIDANCE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0900Z 16.5N 117.8W    45 KT
 12HR VT     10/1800Z 17.5N 117.6W    45 KT
 24HR VT     11/0600Z 18.4N 116.8W    45 KT
 36HR VT     11/1800Z 19.1N 115.9W    40 KT
 48HR VT     12/0600Z 19.9N 114.9W    35 KT
 72HR VT     13/0600Z 21.0N 113.0W    25 KT...DISSIPATING
 96HR VT     14/0600Z 22.5N 111.0W    20 KT...REMNANT LOW
120HR VT     15/0600Z...DISSIPATED
 
$$
FORECASTER KNABB/WILLIS
 
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