000 AXNT20 KNHC 112342 AAA TWDAT TROPICAL WEATHER DISCUSSION...AMENDMENT NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST TUE DEC 11 2007 ...TRANSITION OLGA TO TROPICAL STORM AND UPDATE POSITION... TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS... WEATHER OBSERVATIONS...AND RADAR. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2145 UTC ...SPECIAL FEATURE... DATA FROM A HURRICANE HUNTER PLANE INDICATE THAT THE STRONGER WINDS ARE NOW CLOSER TO THE CENTER SUGGESTING THAT OLGA HAS TRANSITIONED TO A TROPICAL STORM. TROPICAL STORM OLGA IS CENTERED NEAR 18.8N 69.5W AT 12/0000 UTC WHICH IS INLAND OVER THE DOMINICAN REPUBLIC ABOUT 26 NM NNE OF SANTO DOMINGO AND JUST S OF BAHIA DE SAMANA IN THE DOMINICAN REPUBLIC MOVING W AT 11 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB. MAXIMUM SUSTAINED WIND SPEED HAS INCREASED TO 50 KT WITH GUSTS TO 60 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC AND THE NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS. THIS SYSTEM LACKS THE DEEP CONVECTION USUALLY ASSOCIATED WITH A TROPICAL SYSTEM. HOWEVER A BROAD AREA OF HEAVY RAINS WITH EMBEDDED THUNDERSTORMS COVERS THE AREA FROM 18N-22N BETWEEN 65W-71W WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 17N-23N BETWEEN 62W-73W. THE PRIMARY THREAT FROM OLGA REMAINS HEAVY RAINFALL MAINLY OVER HISPANIOLA TONIGHT AND IS REDUCING FREQUENCY OVER PUERTO RICO AS WELL AS MOVING OVER THE TURKS AND CAICOS. THESE RAINS COULD PRODUCE FLASH FLOODS AND MUD SLIDES. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 6N8W 5N20W 7N40W 6N58W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 180 NM OF THE ITCZ AXIS BETWEEN 22W-38W AND S OF 4N W OF 41W TO INLAND OVER SOUTH AMERICA. DISCUSSION... GULF OF MEXICO... BROAD UPPER RIDGE COVERS THE ENTIRE GULF ANCHORED BY AN UPPER HIGH OVER NE FLORIDA. A SURFACE RIDGE AXIS EXTENDS FROM THE W ATLC ACROSS THE SE US TO E TEXAS ALSO COVERING THE ENTIRE GULF. DRY STABLE AIR COVERS THE GULF EXCEPT WITH SOME ISOLATED LOW LEVEL RETURN FLOW SHOWERS DOTTING THE CENTRAL GULF. OTHERWISE SKIES ARE CLEAR THIS EVENING. CARIBBEAN SEA... THE MOST SIGNIFICANT FEATURE THIS EVENING IS TROPICAL STORM OLGA IN THE SPECIAL FEATURES ABOVE. OTHERWISE...BROAD UPPER RIDGE COVERS THE CARIBBEAN S OF 16N ANCHORED IN THE W TROPICAL ATLC. BROAD UPPER RIDGE OVER THE GULF OF MEXICO IS INDUCING AN UPPER TROUGH OVER THE N CARIBBEAN EXTENDING FROM W OF OLGA ALONG THE LENGTH OF CUBA TO THE YUCATAN CHANNEL. MODERATE/STRONG NE SURFACE WINDS COVER THE CARIBBEAN DUE TO THE TIGHT PRESSURE GRADIENT IN PART DUE TO THE STRONG SURFACE RIDGE ACROSS THE ATLC AND TROPICAL STORM OLGA. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 90 EITHER SIDE OF THE LESSER ANTILLES DUE TO THE UPPER AND LOWER LEVEL CONVERGENCE OVER THE AREA. THE REMAINDER OF THE CARIBBEAN REMAINS MOSTLY CLEAR THIS EVENING WITH SOME ISOLATED SHOWERS INLAND AND WITHIN 60 NM ALONG THE COAST OF PANAMA...COSTA RICA...AND NICARAGUA DUE TO THE CLOSE PROXIMITY OF THE ITCZ AXIS IN THE E PACIFIC REGION. ATLANTIC OCEAN... THE MOST SIGNIFICANT FEATURE THIS EVENING IS TROPICAL STORM OLGA IN THE SPECIAL FEATURES ABOVE. OTHERWISE...BROAD UPPER RIDGE COVERING THE GULF OF MEXICO EXTENDS OVER THE FAR W ATLC W OF 75W. THE UPPER HIGH ASSOCIATED WITH OLGA IS PRODUCING GENEROUS OUTFLOW MAINLY TO THE N OF THE STORM. BROAD UPPER TROUGH COVERS THE CENTRAL AND E ATLC N OF 20N FROM 17W-55W WITH AN UPPER LOW CENTERED NEAR 27N25W. A SURFACE TROUGH EXTENDS ALONG THE NW COAST OF AFRICA FROM WESTERN SAHARA TO THE STRAITS OF GIBRALTAR. AN UPPER HIGH IS IN THE TROPICAL ATLC NEAR 3N42W COVERING THE AREA S OF 20N FROM OVER THE CARIBBEAN TO AFRICA PROVIDING UPPER DIFFLUENCE ENHANCING THE ACTIVITY IN THE ITCZ SECTION ABOVE. BROAD SURFACE RIDGE COVERS THE ENTIRE ATLC AND THE GULF OF MEXICO EXCEPT IN THE IMMEDIATE VICINITY OF TROPICAL STORM OLGA AND WITH A WEAKNESS NEAR THE SURFACE TROUGH ALONG THE COAST OF AFRICA. $$ WALLACE