000 AXNT20 KNHC 122352 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST WED 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC ...SPECIAL FEATURE... TROPICAL STORM OLGA WAS DOWNGRADED TO TROPICAL DEPRESSION AT 12/2100 UTC. TROPICAL DEPRESSION OLGA IS CENTERED NEAR 18.9N 76.9W AT 12/2100 UTC WHICH IS 55 NM NORTH OF KINGSTON JAMAICA AND ABOUT 245 NM EAST OF GRAND CAYMAN MOVING W AT 20 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND SPEED HAS DECREASED TO 30 KT WITH GUSTS TO 40 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. BROAD AREA OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS COVERS PORTIONS OF THE N/CENTRAL CARIBBEAN AND THE SW ATLC FROM 17N-24N BETWEEN 69W-78W INCLUDING JAMAICA...PORTIONS OF CUBA AND HISPANIOLA...AS WELL AS THE TURKS AND CAICOS. THE UPPER LEVEL SHEAR THAT HAS BEEN EXPECTED IS NOW WEAKENING OLGA AND IT IS NOT EXPECTED TO REGENERATE. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 6N8W 4N13W 4N25W 3N34W 5N45W 3N52W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM THE EQUATOR TO 5W E OF 20W TO ACROSS THE PRIME MERIDIAN AND FROM 1N-7N BETWEEN 23W-38W. CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION ARE FROM 6N-11N BETWEEN 48W-50W INCLUDING PORTIONS OF SOUTH AMERICA. DISCUSSION... GULF OF MEXICO... A DEEP LAYERED TROUGH IS OVER THE CENTRAL PLAIN STATES ACROSS MEXICO INTO THE E PACIFIC REGION EXTENDING A COLD FRONT ALONG THE TEXAS COAST. THIS FRONT WILL MOVE INTO THE GULF OVERNIGHT AND BEGIN TO WASHOUT AND MOVE NORTH AS A WARM FRONT ON FRI. A SURFACE RIDGE AXIS EXTENDS FROM THE W ATLC OVER THE SE US AHEAD OF THE FRONT WITH A 1024 MB HIGH OVER E ALABAMA. BROAD UPPER RIDGE DOMINATES THE GULF AND EXTENDS INTO THE ATLC. DRY STABLE AIR DOMINATES THE GULF EXCEPT WITH SOME ISOLATED LOW LEVEL RETURN FLOW SHOWERS DOTTING THE CENTRAL GULF AND THE STRAITS OF FLORIDA. OTHERWISE SKIES REMAIN CLEAR THIS EVENING. CARIBBEAN SEA... THE MOST SIGNIFICANT FEATURE THIS EVENING REMAINS TROPICAL DEPRESSION OLGA IN THE SPECIAL FEATURES ABOVE. OTHERWISE...BROAD UPPER RIDGE COVERS THE CARIBBEAN ANCHORED IN THE W TROPICAL ATLC. MODERATE/STRONG N TO 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 DEPRESSION OLGA. SCATTERED SHOWERS ARE OVER THE SE CARIBBEAN S OF 13N E OF 70W ACROSS THE WINDWARD ISLANDS AND WITHIN 120 NM ALONG THE COAST OF PANAMA AND COSTA RICA. OTHERWISE SKIES REMAIN CLEAR THIS EVENING. ATLANTIC OCEAN... THE MOST SIGNIFICANT FEATURE THIS EVENING IS TROPICAL DEPRESSION OLGA IN THE SPECIAL FEATURES ABOVE. THE UPPER HIGH ASSOCIATED WITH OLGA IS PRODUCING GENEROUS OUTFLOW MAINLY N OF THE GREATER ANTILLES BETWEEN 65W-75W. BROAD UPPER RIDGE DOMINATES THE W ATLC W OF 50W WHILE A BROAD UPPER TROUGH AXIS IS IN THE CENTRAL EXTENDING THROUGH 32N32W TO 23N37W. AN CUTOFF UPPER LOW IS CENTERED W OF THE CANARY ISLANDS NEAR 27N23W WITH A SURFACE TROUGH EXTENDING JUST INLAND ALONG THE NW COAST OF AFRICA. AN UPPER HIGH IS IN THE TROPICAL ATLC NEAR 2N46W COVERING THE TROPICS S OF 16N FROM OVER THE CARIBBEAN TO AFRICA PROVIDING UPPER DIFFLUENCE ENHANCING THE ACTIVITY ALONG THE COAST OF SOUTH AMERICA IN THE ITCZ SECTION ABOVE. BROAD SURFACE RIDGE COVERS W OF 20W AND THE GULF OF MEXICO EXCEPT IN THE IMMEDIATE VICINITY OF TROPICAL DEPRESSION OLGA. $$ WALLACE