000 AXNT20 KNHC 091817 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT WED MAY 09 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN 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... SUBTROPICAL STORM ANDREA IS CENTERED NEAR 30.8N 79.3W AT 09/1500 UTC OR 140 NM SE OF SAVANNAH GEORGIA MOVING W AT 3 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/ WTNT21 KNHC FOR MORE DETAILS. AN AIR FORCE RECONNAISSANCE PLANE HAS INVESTIGATED ANDREA OFF THE SOUTHEAST U.S. COAST. THE INITIAL LEG OF THE MISSION WAS FLOWN AT 300 MB FROM WEST TO EAST OVER THE CIRCULATION CENTER...AND SEVERAL DROPSONDES WERE RELEASED. THE TEMPERATURE PROFILES REVEALED A RATHER FLAT THERMAL CROSS-SECTION...NOT INDICATING A DISCERNIBLE WARM OR COLD CORE AT ANY VERTICAL LEVEL. THE WIND PROFILES... HOWEVER...SHOWED WINDS INCREASING WITH HEIGHT IN THE WESTERN HALF OF THE CIRCULATION AND DECREASING WITH HEIGHT IN THE EASTERN HALF. GOES IMAGERY INDICATES THAT...COMPARED TO YESTERDAY...THE THUNDERSTORM ACTIVITY HAS CONSOLIDATED CLOSER TO THE CENTER...BUT PRIMARILY IN THE EASTERN SEMICIRCLE. THERE IS ALSO A SLIGHT HINT OF UPPER-LEVEL OUTFLOW WHICH WAS COMPLETELY ABSENT YESTERDAY. SUBSEQUENTLY HOWEVER...CONVECTION HAS DECREASED IN THE PAST HOUR. ISOLATED MODERATE CONVECTION IS WITHIN 120 NM OF THE CENTER. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 7N12W 6N20W 1N40W EQ50W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 1N-7N BETWEEN 18W-28W. SCATTERED MODERATE CONVECTION IS FROM 3S-3N BETWEEN 28W-40W. WIDELY SCATTERED MODERATE CONVECTION IS ALONG THE COAST OF SOUTH AMERICA FROM 3S-3N BETWEEN 40W-50W. ...DISCUSSION... GULF OF MEXICO... ANDREA IS ADVECTING DRY 10-15 KT NLY SURFACE WINDS OVER THE ERN GULF OF MEXICO. SMOKE PLUMES ORIGINATING FROM FIRES IN FLORIDA AND S GEORGIA CONTINUE TO AFFECT THE E/SE GULF OF MEXICO AND FLORIDA. VISIBILITIES ARE 3-5 NM AT TIMES IN SOUTH FLORIDA AND THE KEYS...S OF 27N. SEAS ARE MOSTLY IN THE 2-4 FT RANGE. FURTHER W...A 1017 MB HIGH IS CENTERED S OF LOUISIANA NEAR 28N92W PRODUCING FAIR WEATHER AND ANTICYCLONIC 5-10 KT WINDS. IN THE UPPER LEVELS...A TROUGH IS OVER THE E GULF E OF 88W WITH STRONG SUBSIDENCE...WHILE A RIDGE IS OVER THE W GULF W OF 88W WITH SIGNIFICANT UPPER LEVEL MOISTURE. RIDGE AXIS IS ALONG 95W. EXPECT THE CENTER OF ANDREA TO COME CLOSER TO THE FLORIDA COAST AND THUS PRODUCE SOME CONVECTION OVER THE NE PART OF THE STATE LATER TONIGHT. ALSO EXPECT SELY RETURN FLOW TO PRODUCE SCATTERED SHOWERS ALONG THE COAST OF NE MEXICO AND S TEXAS. CARIBBEAN SEA... WEAK PRES PATTERN IN THE WRN CARIB CONTINUES TO PRODUCE LIGHT NE WINDS GENERALLY IN THE 5-10 KT RANGE. THE TRADES INCREASE TO 15 KT IN THE E CARIB AS RIDGING FROM THE AZORES HIGH HAS TIGHTENED THE GRADIENT. SCATTERED MODERATE CONVECTION IS OVER HISPANIOLA FROM 15N-20N BETWEEN 68W-75W. WIDELY SCATTERED MODERATE CONVECTION IS ALSO ALONG THE COAST OF PANAMA FROM 9N-11N BETWEEN 79W-82W. IN THE UPPER LEVELS...A TROUGH IS OVER THE W CARIBBEAN W OF 72W WITH STRONG SUBSIDENCE. A RIDGE IS OVER THE E CARIBBEAN E OF 72W WITH SIGNIFICANT UPPER LEVEL MOISTURE. EXPECT LITTLE CHANGE OVER THE NEXT 24 HOURS. ATLANTIC... SEE THE SPECIAL SECTION ABOVE ABOUT ANDREA. FURTHER E... NUMEROUS TSTMS ARE OVER THE DISCUSSION AREA N OF 20N BETWEEN 65W-70W MOSTLY DUE TO UPPER DIFFLUENCE BETWEEN THE VERTICALLY STACKED ANDREA OFF THE SOUTHEAST U.S. AND UPPER LEVEL RIDGING EXTENDING N ALONG 60W. A SURFACE TROUGH IS OVER THE CENTRAL ATLANTIC ALONG 32N41W 26N50W. SCATTERED SHOWERS ARE WITHIN 30 NM OF THE TROUGH AXIS. A 1026 MB HIGH IS JUST W OF PORTUGAL NEAR 40N14W PRODUCING WIDESPREAD FAIR WEATHER AND MODERATE TRADES ACROSS THE CENTRAL AND ERN ATLANTIC. SAHARAN DUST HAS SPREAD TO 40W...ALTHOUGH IS THICKEST E OF 30W. THIS DUST IS ERODING THE TYPICAL STRATOCUMULUS DECK ASSOCIATED WITH THE SUBTROPICAL RIDGE. $$ FORMOSA