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Tropical Storm NICHOLAS


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TROPICAL STORM NICHOLAS DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT FRI OCT 17 2003
 
MICROWAVE AND QUIKSCAT AMBIGUITIES INDICATE THAT THE CENTER OF
NICHOLAS REMAINS NEAR THE SOUTHWEST EDGE OF THE DEEP CONVECTION. 
CURRENT DVORAK T-NUMBER WIND EQUIVALENTS FROM TAFB...SAB...AND AFWA
ARE 65...55...AND 55 KT...RESPECTIVELY.  THE 22Z QUIKSCAT PASS DID
NOT CONTAIN ANYTHING TO SUGGEST THAT NICHOLAS HAS STRENGTHENED...SO
THE INITIAL INTENSITY IS HELD AT 55 KT.  ALTHOUGH THE CIRRUS
OUTFLOW PATTERN APPEARS IMPRESSIVE...SOUTHWESTERLY SHEAR CONTINUES
TO UNDERCUT THIS OUTFLOW.

WITH AN INITIAL MOTION ESTIMATE OF 340/5...IT APPEARS THAT NICHOLAS
HAS SLOWED AND TURNED A BIT TO THE RIGHT.  NICHOLAS REMAINS TO THE
SOUTHEAST OF A WEAK MID-LEVEL RIDGE OF HIGH PRESSURE THAT MAY
ALREADY BE STARTING TO BLOCK ITS MOTION.  EMBEDDED WITHIN AN
ENVIRONMENT OF UPPER-LEVEL SOUTHWESTERLIES AND LOW-LEVEL
EASTERLIES...NICHOLAS WILL MOVE MORE NORTHWARD WHEN IT CAN STAY
WELL-CONNECTED VERTICALLY...AND MORE WESTWARD WHEN IT SHEARS.  THE
GLOBAL MODELS INDICATE THAT THE SHEAR WILL NOT DIMINISH
SIGNIFICANTLY OVER THE NEXT COUPLE OF DAYS AND THEN INCREASE NEAR
THE END OF THE FORECAST PERIOD.   THERE IS CONSIDERABLE SPREAD IN
THE MODEL GUIDANCE...WITH THE GFS TAKING A VERY WEAK SYSTEM SHARPLY
WESTWARD AND THE GFDL TAKING A HURRICANE TO THE NORTH-NORTHEAST. 
THE UKMET...WHICH HAS OUTPERFORMED THE OTHER MODELS WITH
NICHOLAS...IS IN BETWEEN BUT GENERALLY FAVORS THE WEAK AND WEST
OPTION.  THE OFFICIAL FORECAST IS IN BEST AGREEMENT WITH THE UKMET
AND THE SHALLOW BAM...AND CALLS FOR A TRACK THAT GRADUALLY TURNS TO
THE LEFT AS THE CYCLONE WEAKENS.  ALTHOUGH NOT INDICATED
BELOW...NICHOLAS COULD STILL BECOME A HURRICANE DURING THE NEXT DAY
OR TWO IF THE SHEAR WERE TO UNEXPECTEDLY DIMINISH.

FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0300Z 16.7N  48.5W    55 KT
 12HR VT     18/1200Z 17.4N  48.7W    55 KT
 24HR VT     19/0000Z 18.2N  49.3W    55 KT
 36HR VT     19/1200Z 18.8N  49.8W    55 KT
 48HR VT     20/0000Z 19.5N  50.5W    50 KT
 72HR VT     21/0000Z 20.5N  52.0W    45 KT
 96HR VT     22/0000Z 21.0N  53.5W    40 KT
120HR VT     23/0000Z 21.5N  55.5W    35 KT
 
 
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