000 AXNT20 KNHC 121801 TWDAT TROPICAL WEATHER DISCUSSION... NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST THU DEC 12 2007 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC ...SPECIAL FEATURE... TROPICAL STORM OLGA EMERGED INTO THE WINDWARD PASSAGE EARLY THIS MORNING. CURRENTLY...THIS TROPICAL STORM IS WEAKENING BUT RAINS CONTINUE OVER HISPANIOLA. THE WEATHER SERVICE IN DOMINICAN REPUBLIC REPORTED RAINFALL AMOUNTS BETWEEN 4-7 INCHES...100-170 MM...DURING THE LAST 24 HOURS WITH THE HEAVIEST RAINFALL ACCUMULATIONS OVER THE MOUNTAINOUS TERRAIN. THE CITY OF PONCE IN SOUTH PUERTO RICO REPORTED 11 INCHES OF RAIN IN TWO DAYS. AT 12/1800 UTC...OLGA WAS LOCATED NEAR 19.0N 76.0W OR ABOUT 75 MILES...135 KM...SW OF GUANTANAMO CUBA MOVING W AT 20 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009 MB. MAXIMUM SUSTAINED WIND SPEED HAS DECREASED TO 35 KT WITH GUSTS TO 45 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. OLGA LACKS THE CONVECTION REQUIRED OF A TROPICAL CYCLONE...AND BASED ON VISIBLE SATELLITE IMAGERY PROBABLY ALSO LACKS A CLOSED SURFACE CIRCULATION. A QUIKSCAT PASS FROM AROUND 10Z...AS WELL AS SURFACE OBSERVATIONS SUGGEST THAT THERE REMAINS A BAND OF TROPICAL STORM FORCE WINDS JUST EAST OF THE TURKS AND CAICOS ISLANDS. BASED ON THIS DATA...THE TROPICAL STORM STATUS REMAINS IN PLACE. THE PRIMARY THREAT FROM OLGA CONTINUES TO BE HEAVY RAINFALL AND LIFE-THREATENING FLASH FLOODS AND MUD SLIDES IN HISPANIOLA. SOME OF THESE RAINS SHOULD SPREAD OVER EASTERN CUBA THIS AFTERNOON. WEAKENING TO A REMNANT LOW IS EXPECTED IN THE NEXT DAY OR TWO AS NORTHWESTERLY SHEAR DEVELOPS OVER THE SYSTEM. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 6N10W 5N25W 4N35W 5N44W 4N52W. SCATTERED MODERATE CONVECTION IS WITHIN 200 NM S OF THE AXIS E OF 16W AND WITHIN 150 NM EITHER SIDE OF AXIS BETWEEN 25W-36W. A CLUSTER OF MODERATE CONVECTION IS N OF AXIS NEAR 8N50W. DISCUSSION... GULF OF MEXICO... A MID TO UPPER LEVEL RIDGE REMAINS IN CONTROL OF THE REGION WHILE A WEAKENING UPPER LOW CONTINUES ITS SLOW W MOVEMENT OVER THE BAHAMAS. THIS PATTERN IS ENHANCING DRY STABLE AIR ALOFT... PARTICULARLY OVER THE SE GULF AND SOUTH-CENTRAL FLORIDA LIMITING THE FORMATION OF ANY DEEP CLOUDINESS. AT THE SURFACE...RIDGING EXTENDS SW INTO THE AREA FROM A 1026 MB HIGH LOCATED OVER SOUTHERN GEORGIA. A QUIKSCAT PASS FROM AROUND 12Z SHOWED LIGHT TO MODERATE E TO SE WINDS OVER MOST...EXCEPT SLY IN THE NW CORNER AHEAD OF A SLOW MOVING COLD FRONT OVER TEXAS. SOME PATCHES OF LOW LEVEL MOISTURE ARE SEEN MAINLY ACROSS THE CENTRAL GULF IN ASSOCIATION WITH THE RETURN FLOW. A COUPLE OF FRONTS ARE EXPECTED TO MOVE INTO THE GULF BETWEEN TODAY AND THE UPCOMING WEEKEND. THE FIRST ONE IS WEAK COLD FRONT MOVING OFF THE TEXAS COAST LATE TODAY AND TONIGHT. A STRONGER COLD FRONT IS FORECAST TO MOVES OFF TEXAS COAST EARLY SATURDAY BRINGING IN STRONG WINDS AND ROUGH SEAS. CARIBBEAN SEA... BANDS OF HEAVY RAIN...ASSOCIATED WITH TROPICAL STORM OLGA... CONTINUES TO AFFECT HISPANIOLA AND THE SE BAHAMAS...AND ARE SPREADING OVER EASTERN CUBA. THIS TROPICAL CYCLONE IS EXPECTED TO PRODUCE ADDITIONAL RAINFALL ACCUMULATIONS OF 1 TO 2 INCHES OVER THE SOUTHEASTERN BAHAMAS. RAINFALL AMOUNTS OF 2 TO 4 INCHES ARE POSSIBLE OVER EASTERN CUBA...WITH ISOLATED MAXIMUM ACCUMULATIONS OF 8 INCHES. RAINFALL AMOUNTS OF 4 TO 6 INCHES ARE POSSIBLE OVER HISPANIOLA...WITH ISOLATED MAXIMUM AMOUNTS OF 10 INCHES. THE SAN JUAN DOPPLER RADAR IS SHOWING SCATTERED SHOWERS AND ISOLATED TSTMS OVER THE UK/US VIRGIN ISLANDS...PUERTO RICO AND REGIONAL WATERS MOVING NW UNDER A SELY WIND FLOW. THESE WINDS WILL CONTINUE TO ADVECT TROPICAL MOISTURE INTO THOSE ISLANDS THIS AFTERNOON. LATEST VIS SATELLITE IMAGERY REVEALS THAT THE CENTER OF OLGA IS NOW MOVING BETWEEN THE SOUTH COAST OF EASTERN CUBA AND JAMAICA. PUNTA MAISI IN CUBA REPORTED SUSTAINED WINDS OF 35 KT...65 KM/HR WITH GUSTY WINDS OF 43 KT...80 KM/HR. NARROW BANDS OF CLOUDS WITH EMBEDDED SHOWERS ARE OVER THE REMAINDER OF THE BASIN ASSOCIATED WITH THE OVERALL CIRCULATION OF OLGA. ELSEWHERE...A LARGE AREA OF MODERATE TO STRONG CONVECTION HAS DEVELOPED OVER AND JUST E OF THE WINDWARD ISLANDS COVERING FROM 7N-12N BETWEEN 55W AND THE COAST OF SOUTH AMERICA. THIS ACTIVITY IS ASSOCIATED WITH A DIFFLUENT PATTERN ALOFT AND A LOW-LEVEL ELY SURGE. DUE TO THE PRESENCE OF TROPICAL STORM OLGA...THE TRADE WIND FLOW IS LIGHTER THIS AFTERNOON ACROSS MUCH OF THE SOUTH-CENTRAL WHILE STRONG NELY WINDS PERSIST OVER THE NW CARIBBEAN. ALOFT...A RIDGE DOMINATES THE ENTIRE AREA...INCLUDING ALSO CENTRAL AMERICA AND NORTHERN SOUTH AMERICA. ATLANTIC OCEAN... THE FORECAST AREA IS FAIRLY QUIET THIS AFTERNOON WITH MODERATE TO STRONG RIDGING DOMINATING THE SFC PATTERN SUPPORTED BY A 1027 MB HIGH LOCATED SE OF BERMUDA NEAR 31N62W. THERE IS A SLIGHT WEAKNESS IN THE RIDGE DUE TO A COLD FRONT N OF THE AREA AND A COASTAL TROUGH NEAR THE AFRICAN COAST N OF 20N. A LARGE AREA OF 20-30 KT NE TO E WINDS EXTENDS NWD TO 26N BETWEEN 60W-78W DUE TO THE TIGHT PRES PATTERN BETWEEN THE BERMUDA HIGH AND OLGA. SIMILAR WIND SPEEDS ARE FOUND BETWEEN 50W AND THE LESSER ANTILLES FROM 11N-22N. THE MID AND UPPER PATTERN CONSISTS OF A LONGWAVE RIDGE/TROUGH IN THE SUBTROPICS AND FAIRLY ZONAL FLOW ACROSS THE TROPICAL BELT. AN UPPER-LEVEL LOW IS JUST WEST OF THE CANARY ISLANDS. THIS LOW IS GENERATING ISOLATED SHOWERS. A JET STREAM BRANCH WITH CORE WINDS OF AROUND 85 KT IS SOUTH OF 20N...DRAWING UPPER LEVEL MOISTURE/HIGH CLOUDS FROM SOUTH AMERICA ALL THE WAY EAST ACROSS THE TROPICAL ATLC TO THE WEST COAST OF AFRICA. $$ GR