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Tropical Storm NORMA

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TROPICAL STORM NORMA DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 PM PDT SUN SEP 25 2005
 
THE LOW LEVEL CENTER REMAINS PARTIALLY OBSCURED BY CIRRUS AND STILL
APPEARS TO BE LOCATED NORTHEAST OF THE DEEPEST CONVECTION... WHICH
HAS LESSENED DURING THE PAST FEW HOURS.  THERE IS ONE REMAINING
CONVECTIVE BURST WITH TOPS COLDER THAN -70C.  DVORAK INTENSITY
ESTIMATES AT 00Z WERE 35-45 KT... AND THE ADVISORY INTENSITY IS
ADJUSTED DOWNWARD TO 40 KT. EASTERLY SHEAR ON THE SOUTH SIDE OF AN
UPPER LEVEL ANTICYCLONE CONTINUES TO PREVENT THE SYSTEM FROM
ORGANIZING. EVEN THOUGH NORMA MIGHT GAIN ENOUGH LATITUDE IN A DAY
OR TWO TO WHERE THE SHEAR IS A LITTLE WEAKER... OCEAN TEMPERATURES
WILL ONLY GET COOLER ALONG THE WAY. GRADUAL WEAKENING APPEARS
LIKELY TO CONTINUE AS FORECAST BY THE SHIPS AND GFDL GUIDANCE. THE
NEW OFFICIAL FORECAST ANTICIPATES AN EVEN FASTER PACE OF DECLINE
THAN THE PREVIOUS ADVISORY.
 
THE ESTIMATED INITIAL MOTION IS 310/7... STILL NORTHWESTWARD BUT
WITH A SLIGHTLY MORE WESTERLY COMPONENT THAN EARLIER TODAY.  THE
CURRENT STEERING IS PROVIDED BY FLOW AROUND THE SOUTHWESTERN
PERIPHERY OF A MID-LEVEL RIDGE CENTERED OVER TEXAS.  THIS RIDGE IS
FORECAST BY THE DYNAMICAL MODELS TO BUILD WESTWARD IN A COUPLE OF
DAYS AS A LOW CURRENTLY OFFSHORE CALIFORNIA MOVES INLAND.  AS A
RESULT... A WEAKENING NORMA SHOULD BE FORCED TO THEN TURN
WESTWARD... ESPECIALLY SINCE IT WILL LIKELY BE WEAKER AND STEERED
INCREASINGLY BY THE LOW LEVEL TRADE WIND FLOW.  THE NEW OFFICIAL
TRACK FORECAST IS ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE SINCE
THE MODELS MIGHT HAVE A SLIGHT EAST BIAS FOR A SYSTEM UNDER
EASTERLY SHEAR.  THIS TRACK IS ALSO A BIT SOUTH OF AND SLOWER THAN
THE PREVIOUS ONE LATE IN THE FORECAST PERIOD... LEANING MORE TOWARD
THE GFDL AND GFS THAN THE NOGAPS... SINCE THE LATTER DEPICTS WHAT
APPEARS TO BE TOO STRONG OF A CIRCULATION FOR WHAT IS EXPECTED TO
BE A DEPRESSION AND EVENTUAL REMNANT LOW.
 
FORECASTER KNABB
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      26/0300Z 18.7N 113.0W    40 KT
 12HR VT     26/1200Z 19.4N 113.9W    40 KT
 24HR VT     27/0000Z 20.3N 114.9W    35 KT
 36HR VT     27/1200Z 21.0N 116.0W    30 KT
 48HR VT     28/0000Z 21.1N 117.0W    25 KT...DISSIPATING
 72HR VT     29/0000Z 21.0N 118.5W    20 KT...REMNANT LOW
 96HR VT     30/0000Z 20.5N 120.5W    20 KT...REMNANT LOW
120HR VT     01/0000Z 20.0N 123.0W    20 KT...REMNANT LOW
 
 
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