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Subtropical Storm OLGA (Text)

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SUBTROPICAL STORM OLGA DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172007
400 PM EST TUE DEC 11 2007
 
AN ASCAT PASS FROM LATE THIS MORNING SUGGESTS THAT THE WINDS TO THE
NORTH OF THE CENTER MAY HAVE DECREASED A LITTLE...BUT A
RECONNAISSANCE AIRCRAFT WILL REACH THE AREA SHORTLY...AND I WOULD
PREFER TO WAIT FOR THEIR REPORTS BEFORE ADJUSTING THE ESTIMATED
INTENSITY.  GRAND TURK ISLAND RECENTLY REPORTED A SUSTAINED WIND OF
31 KT.  THERE HAS BEEN AN INCREASE IN CONVECTION NEAR THE
CENTER OVER THE PAST COUPLE OF HOURS...AND THE ASCAT DATA ALSO
SUGGEST THAT THE RADIUS OF MAXIMUM WINDS MAY BE DECREASING.  IF
THIS IS CONFIRMED BY THE AIRCRAFT...OLGA COULD BE CLASSIFIED AS A
TROPICAL CYCLONE THIS EVENING.
 
THE CENTER OF OLGA MADE LANDFALL IN THE DOMINICAN REPUBLIC JUST TO
THE SOUTH OF PUNTA CANA AROUND 18Z.  THE MOTION OF THE CENTER HAS
BEEN ERRATIC...BUT OVERALL IS ESTIMATED TO BE 270/11.  THERE HAS
BEEN LITTLE CHANGE TO THE SYNOPTIC REASONING...WHICH CALLS FOR OLGA
TO BE STEERED BASICALLY WESTWARD TO THE SOUTH OF A LOW- TO
MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC.  AFTER 48 HOURS...OLGA
WILL BE ROUNDING THE PERIPHERY OF THIS RIDGE...BUT THERE IS LIKELY
TO BE LITTLE LEFT OF THE CYCLONE BY THEN.  THE OFFICIAL FORECAST IS
VERY CLOSE TO THE GFS AND THE DYNAMICAL MODEL CONSENSUS.
 
WATER VAPOR IMAGERY SUGGESTS THAT WESTERLY SHEAR IS BEGINNING TO
INCREASE OVER THE CENTER OF CIRCULATION.  GLOBAL MODELS CONTINUE TO
INDICATE THAT THE UPPER LOW TO THE WEST OF THE CYCLONE WILL
WEAKEN...ALLOWING THE SHEAR TO INCREASE.  THIS...COUPLED WITH THE
INTERACTION OF THE CENTER WITH HISPANIOLA...SHOULD RESULT IN A
DECAY OF THE SYSTEM.  A STRONG PRESSURE GRADIENT IS LIKELY TO
PERSIST TO THE NORTH OF THE DECAYING CYCLONE...HOWEVER...AND WINDS
THERE WILL BE SLOW TO DIMINISH.

THE PRIMARY THREAT FROM OLGA IS HEAVY RAINFALL...WHICH IS
ALREADY PRODUCING LIFE-THREATENING MUD SLIDES IN PUERTO RICO.
THESE RAINS WILL BE SPREADING ACROSS HISPANIOLA TONIGHT...WHERE
FLASH FLOODS AND MUD SLIDES ARE ALSO LIKELY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/2100Z 18.5N  68.8W    40 KT...INLAND
 12HR VT     12/0600Z 18.5N  71.4W    35 KT...INLAND
 24HR VT     12/1800Z 18.6N  74.5W    30 KT...OVER WATER
 36HR VT     13/0600Z 18.9N  77.8W    25 KT...REMNANT LOW
 48HR VT     13/1800Z 19.2N  80.5W    25 KT...REMNANT LOW
 72HR VT     14/1800Z 19.5N  83.0W    25 KT...REMNANT LOW
 96HR VT     15/1800Z...DISSIPATED
 
$$
FORECASTER FRANKLIN
 
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