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Subtropical Storm OLGA


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SUBTROPICAL STORM OLGA DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172007
400 AM EST TUE DEC 11 2007
 
WSR-88D RADAR IMAGERY FROM SAN JUAN PUERTO RICO REVEALS THAT THE
CENTER OF OLGA HAS BEEN MOVING ALONG THE NORTHERN COAST OF THAT
ISLAND FOR THE PAST SEVERAL HOURS...AT A WESTWARD HEADING OF 270
DEGREES AT ABOUT 15 KT.  OLGA SEEMS TO HAVE BEGUN A GRADUAL
DECLINE...GIVEN A SLIGHT THINNING OF THE RAIN SHIELD IN THE RADAR
IMAGERY...WARMING CLOUD TOPS IN GOES INFRARED IMAGERY...AND A
DECREASE IN LONG-RANGE LIGHTNING RETURNS.  THE INITIAL INTENSITY
REMAINS 40 KT...HOWEVER...BASED ON THE SEVERAL OBSERVATIONS DURING
THE PAST FEW HOURS OF ABOUT 40 KT FROM A FEW SHIPS AND NOAA BUOY
41043.  THIS ESTIMATE IS ALSO CONSISTENT WITH THE MAXIMUM WINDS
FROM A FORTUITOUS ASCAT OVERPASS BACK AT 0206Z.  FOR NOW WE WILL
RETAIN THE SUBTROPICAL DESIGNATION FOR OLGA SINCE WATER VAPOR
IMAGERY SUGGESTS THAT AN ELONGATING UPPER-LEVEL LOW IS SITUATED
ABOVE THE LOW-LEVEL CENTER.  THIS FEATURE APPEARS TO BE
WEAKENING...AND GLOBAL MODELS FORECAST THAT IT WILL DISSIPATE LATER
TODAY...SO OLGA COULD SOON MAKE THE TRANSITION TO A TROPICAL
CYCLONE.

THE TRACK FORECAST IS GENERALLY STRAIGHTFORWARD...SINCE A LOW- TO
MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC WILL LIKELY STEER OLGA ON
A CONTINUED WESTWARD PATH OVER HISPANIOLA AND INTO THE NORTHERN
CARIBBEAN SEA.  THE EXACT PATH OF THE CENTER ITSELF IS OF
RELATIVELY LITTLE CONSEQUENCE IN THIS CASE...SINCE MOST OF THE
HEAVY RAINS AND STRONGEST WINDS ARE WELL REMOVED FROM THE CENTER. 
DUE TO OLGA'S DEGRADED SATELLITE APPEARANCE...SIGNIFICANT
STRENGTHENING PRIOR TO REACHING HISPANIOLA APPEARS UNLIKELY...AND
HEAVY RAINFALL REMAINS THE PRIMARY HAZARD FROM THIS SYSTEM. 
WEAKENING IS THEN FORECAST AS OLGA MOVES ACROSS HISPANIOLA DURING
THE NEXT 24 HOURS...AND AN INCREASE IN WIND SHEAR SHOULD PROHIBIT
RESTRENGTHENING OVER THE WARM WATERS OF THE CARIBBEAN SEA.  IF
OLGA...OR ITS REMNANT LOW...SURVIVES THE NEXT THREE DAYS...THE
MODELS SUGGEST THAT SOME REDEVELOPMENT COULD OCCUR OVER THE WESTERN
CARIBBEAN WHERE UPPER-LEVEL WINDS ARE FORECAST TO LESSEN.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0900Z 18.5N  67.0W    40 KT
 12HR VT     11/1800Z 18.5N  69.4W    40 KT...INLAND
 24HR VT     12/0600Z 18.5N  72.8W    30 KT...NEAR COAST OF HAITI
 36HR VT     12/1800Z 18.5N  76.1W    30 KT...DISSIPATING
 48HR VT     13/0600Z 18.5N  79.4W    25 KT...REMNANT LOW
 72HR VT     14/0600Z 18.5N  83.5W    25 KT...REMNANT LOW
 
$$
FORECASTER KNABB/MAINELLI
 
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