Subtropical Storm OLGA

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SUBTROPICAL STORM OLGA DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172007
1100 PM EDT MON DEC 10 2007
 
SATELLITE IMAGERY AND RADAR DATA FROM THE SAN JUAN WSR-88D INDICATE
THAT THE LOW PRESSURE SYSTEM CENTERED NEAR THE VIRGIN ISLANDS AND
PUERTO RICO HAS ACQUIRED A WELL-DEFINED...THOUGH BROAD...SURFACE
CIRCULATION AND ORGANIZED CONVECTION NOT FAR FROM THE CENTER.  DUE
TO THE PRESENCE OF AN UPPER-LEVEL LOW JUST SOUTH OF THE VIRGIN
ISLANDS...IT IS BEING DESIGNATED A SUBTROPICAL CYCLONE.  NOAA BUOY
41043 NORTH OF THE CENTER HAS TWICE REPORTED 1-MIN AVERAGE WINDS OF
33 KT AT AN ELEVATION OF 5 METERS...WHICH SUGGESTS TROPICAL-STORM
FORCE WINDS ARE OCCURRING AT THE STANDARD SURFACE ELEVATION OF 10
METERS.  BASED ON ALL THIS...THE SYSTEM IS UPGRADED TO SUBTROPICAL
STORM OLGA.  THE INITIAL INTENSITY OF 35 KT IS IN AGREEMENT WITH
SUBTROPICAL INTENSITY ESTIMATES OF 35-40 KT FROM TAFB.

THE INITIAL MOTION IS 275/13.  OLGA IS ON THE SOUTH SIDE OF
A STRONG LOW/MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC...FLORIDA...
AND THE EASTERN GULF OF MEXICO.  THIS RIDGE SHOULD PERSIST FOR THE
NEXT SEVERAL DAYS AND STEER OLGA ON A GENERAL WESTWARD TO WEST-
SOUTHWESTWARD TRACK.  THE FORECAST TRACK FOLLOWS THIS SCENARIO AND
IS DOWN THE MIDDLE OF THE SUITE OF DYNAMICAL MODELS.

OLGA CURRENTLY HAS GOOD OUTFLOW OVER THE NORTHWESTERN SEMICIRCLE...
WITH OUTFLOW AND CONVECTION IN THE SOUTHEASTERN SEMICIRCLE
SUPPRESSED BY THE UPPER-LEVEL LOW.  IN THE SHORT-TERM...THIS
PATTERN IS FAVORABLE FOR SOME STRENGTHENING...AND THE INTENSITY
FORECAST CALLS FOR MODEST INTENSIFICATION BEFORE THE CENTER REACHES
THE DOMINICAN REPUBLIC ON TUESDAY.  AFTER THAT...THE LARGE-SCALE
MODELS FORECAST STRONG WESTERLY VERTICAL WIND SHEAR TO DEVELOP
ALONG THE FORECAST TRACK.  THAT...COMBINED WITH THE LIKELY
DISRUPTION OF THE CIRCULATION BY PASSAGE OVER HISPANIOLA...SHOULD
CAUSE WEAKENING.  THE LARGE-SCALE MODELS FORECAST OLGA TO WEAKEN TO
AN INVERTED TROUGH BY 36-48 HR... WHILE THE SHIPS MODEL FORECASTS
DISSIPATION IN 60 HR.  BASED ON THIS...THE INTENSITY FORECAST CALLS
FOR OLGA TO SURVIVE FOR 48 HR BEFORE DISSIPATING.

AFTER COORDINATION WITH THE WFO SAN JUAN...IT WAS DECIDED THAT
WATCHES AND WARNINGS WERE NOT NEEDED FOR PUERTO RICO SINCE THE
TROPICAL STORM-FORCE WINDS ARE CURRENTLY OVER WATER WELL TO THE
NORTH AND WEST OF THE CENTER.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0300Z 18.5N  65.3W    35 KT
 12HR VT     11/1200Z 18.5N  67.6W    40 KT
 24HR VT     12/0000Z 18.4N  70.6W    30 KT...INLAND
 36HR VT     12/1200Z 18.0N  73.8W    25 KT...OVER WATER
 48HR VT     13/0000Z 17.8N  76.9W    25 KT...DISSIPATING
 72HR VT     14/0000Z...DISSIPATED
 
$$
FORECASTER BEVEN
 
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