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| #163274 (Received by flhurricane at: 3:46 AM 11.Dec.2007) TCDAT2 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 |
