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Tropical Storm NICHOLAS


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TROPICAL STORM NICHOLAS DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT TUE OCT 14 2003
 
DVORAK SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE 45 AND 35
KT...RESPECTIVELY. A QUIKSCAT PASS AT 2030Z CONTAINED A NUMBER OF
30 KT VECTORS OUTSIDE OF THE HEAVY RAIN AREAS. SINCE IT IS QUITE
LIKELY THAT THE WINDS WITHIN THE HEAVIEST CONVECTION ARE SOMEWHAT
HIGHER...THE DEPRESSION IS BEING UPGRADED TO TROPICAL STORM
NICHOLAS...THE 14TH NAMED STORM OF THE YEAR. SINCE 1900...ONLY SIX
SEASONS HAVE PRODUCED MORE STORMS THAN 2003...AND THERE ARE STILL
SIX WEEKS LEFT IN THE SEASON. NICHOLAS IS MAINTAINING VERY COLD
CONVECTION TO THE EAST OF THE CENTER...ALTHOUGH THIS CONVECTION
STILL SHOWS LITTLE OR NO BANDING STRUCTURE. SHEAR ANALYSES FROM THE
UNIVERSITY OF WISCONSIN/CIMSS WEB PAGE SHOWS NICHOLAS IS EMBEDDED
WITHIN AN ENVIRONMENT OF WESTERLY WIND SHEAR.  SOME WESTERLY OR
SOUTHWESTERLY SHEAR SHOULD CONTINUE OVER NICHOLAS...BUT THIS IS NOT
EXPECTED TO PREVENT GRADUAL STRENGTHENING.  THE OFFICIAL FORECAST
IS A BLEND OF THE SHIPS AND GFDL INTENSITY GUIDANCE.

THE INITIAL MOTION IS 295/9.  NICHOLAS IS SOUTH OF A MID- TO
UPPER-LEVEL TROUGH IN THE WESTERLIES BUT WILL SOON BE SEPARATING
FROM THIS FEATURE.  WEAK MID-LEVEL RIDGING LIES TO THE NORTHWEST OF
THE CYCLONE.  THERE IS AN INTERESTING SPLIT IN THE MODEL
GUIDANCE...WITH THE SIMPLER STATISTICAL AND BAM MODELS SHOWING A
CONTINUED WEST-NORTHWEST TRACK BENEATH THIS RIDGE OVER THE NEXT
FIVE DAYS.  ON THE OTHER HAND...THE MODELS WITH MORE COMPLEX
PHYSICS ARE FORECASTING IMMEDIATE SLOWING WITH A TURN TO THE
NORTHWEST.  I AM NOT SURE I UNDERSTAND WHY THE MODELS ARE SPLIT IN
THIS FASHION.  THE WESTERLY SHEAR AND CURRENT DISTRIBUTION OF
CONVECTION WOULD TEND TO SLOW THE FORWARD SPEED AND DRAG THE TRACK
TO THE RIGHT...BUT I CANNOT SAY THAT THIS IS WHAT THE GLOBAL MODELS
ARE TRYING TO DO WITH NICHOLAS.  THERE IS SOME INDICATION IN THESE
MODELS THAT THE AFOREMENTIONED RIDGE MAY WEAKEN SOMEWHAT WITH THE
APPROACH OF A SECOND MID-LATITUDE TROUGH CURRENTLY NEAR 60W.  IN
ANY EVENT...THE OFFICIAL FORECAST CONTINUES TO FOLLOW A
GFS/UKMET/GFDL CONSENSUS.  NEAR THE END OF THE FORECAST
PERIOD...NICHOLAS MAY FIND ITS NORTHWARD PROGRESS BLOCKED BY
WHATEVER REMAINS OF THE RIDGE.

FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/0300Z 11.6N  42.9W    35 KT
 12HR VT     15/1200Z 12.2N  43.8W    40 KT
 24HR VT     16/0000Z 13.1N  44.6W    45 KT
 36HR VT     16/1200Z 14.0N  45.3W    50 KT
 48HR VT     17/0000Z 15.0N  46.0W    55 KT
 72HR VT     18/0000Z 16.5N  47.0W    60 KT
 96HR VT     19/0000Z 18.0N  48.0W    65 KT
120HR VT     20/0000Z 19.0N  49.0W    65 KT
 
 
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