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Tropical Storm OLGA (Text)

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TROPICAL STORM OLGA DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172007
400 AM EST WED DEC 12 2007
 
OLGA HAS LOST SOME ORGANIZATION DURING ITS CROSSING OF HISPANIOLA. 
THERE IS NO SIGNIFICANT CONVECTION NEAR THE CENTER AT THIS TIME...
AND THE CONVECTIVE BANDS OVER THE ATLANTIC TO THE NORTH OF
HISPANIOLA ARE RELATIVELY WEAK.  THERE ARE NO RECENT OBSERVATIONS
FROM NEAR THE CENTER OR FROM THE MAIN AREA OF CONVECTION....SO THE
INITIAL INTENSITY REMAINS 45 KT ON THIS ADVISORY.  THIS MAY BE
GENEROUS. 

THE INITIAL MOTION IS 275/16.  OLGA IS CURRENTLY ON THE SOUTH SIDE
OF A LOW/MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC...FLORIDA...AND
THE EASTERN GULF OF MEXICO.  THE LARGE-SCALE MODELS FORECAST THE
WESTERN END OF THE RIDGE TO GRADUALLY WEAKEN DURING THE NEXT 2-3
DAYS IN ADVANCE OF A DEEP-LAYER TROUGH AND ASSOCIATED COLD FRONT
MOVING THROUGH THE EASTERN UNITED STATES ON DAYS 4-5.  THIS PATTERN
EVOLUTION HAS CAUSED THE TRACK GUIDANCE TO SPLIT INTO TWO CAMPS
AFTER OLGA MOVES WESTWARD FOR 24-48 HR.  THE GLOBAL MODELS FORECAST
OLGA...OR ITS REMNANTS...TO TURN NORTHWARD AND RECURVE INTO THE
COLD FRONT MOVING ACROSS THE GULF OF MEXICO.  ON THE OTHER HAND...
THE GFDL AND HWRF FORECAST OLGA TO TURN SOUTHWEST TOWARDS THE GULF
OF HONDURAS.  THIS FORECAST MAY BE DUE TO THOSE MODELS KEEPING MORE
RIDGING WEST OF OLGA OVER THE YUCATAN PENINSULA...AND FORECASTING A
STRONG CYCLONE IN AN ENVIRONMENT OF UPPER-LEVEL NORTHWESTERLY FLOW. 
THE NEW FORECAST TRACK IS ADJUSTED NORTH OF THE PREVIOUS TRACK...
BUT WILL NOT YET CALL FOR RECURVATURE IN DEFERENCE TO THE GFDL...
HWRF...AND THE PREVIOUS FORECAST.  THE NEW TRACK IS A LITTLE TO THE
SOUTH OF THE VARIOUS CONSENSUS MODELS.

THE DYNAMICAL MODELS AGREE THAT THE UPPER-LEVEL LOW/TROUGH THAT HAS
SO FAR PROTECTED OLGA FROM SHEAR WILL WEAKEN DURING THE NEXT 24 HR
AS A RIDGE BUILDS OVER THE WESTERN CARIBBEAN.  THIS SHOULD CAUSE
STRONG NORTHWESTERLY VERTICAL WIND SHEAR TO DEVELOP OVER THE
SYSTEM.  THE INTENSITY FORECAST IS THUS UNCHANGED FROM THE PREVIOUS
ADVISORY...CALLING FOR OLGA TO WEAKEN TO A DEPRESSION IN 24 HR AND
TO A REMNANT LOW IN 36 HR.  IT SHOULD BE NOTED THAT THE GFDL AND
HWRF FORECAST OLGA TO MOVE INTO AN AREA OF LIGHTER WIND SHEAR IN
THE GULF OF HONDURAS...AND IN CONSEQUENCE BOTH MODELS FORECAST IT
TO BECOME A HURRICANE.  IT SHOULD ALSO BE NOTED THAT THE SHEAR IS
FORECAST TO BE VERY STRONG OVER THE GULF OF MEXICO...SO THE CHANCES
OF OLGA BEING A SIGNIFICANT TROPICAL CYCLONE IN THAT AREA APPEAR
RATHER LOW AT THE MOMENT.
 
THE PRIMARY THREAT FROM OLGA CONTINUES TO BE HEAVY RAINFALL AND
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES IN PUERTO RICO AND 
HISPANIOLA.  THESE RAINS SHOULD BEGIN TO SPREAD OVER EASTERN CUBA
TODAY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/0900Z 19.2N  72.5W    45 KT...INLAND
 12HR VT     12/1800Z 19.4N  74.9W    35 KT...OVER WATER
 24HR VT     13/0600Z 19.6N  77.7W    30 KT
 36HR VT     13/1800Z 19.8N  79.6W    25 KT...REMNANT LOW
 48HR VT     14/0600Z 20.0N  81.5W    25 KT...REMNANT LOW
 72HR VT     15/0600Z 20.5N  84.0W    25 KT...REMNANT LOW
 96HR VT     16/0600Z...DISSIPATED
 
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FORECASTER BEVEN
 
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