000 AXNT20 KNHC 100000 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...SPECIAL FEATURE... SUBTROPICAL STORM ANDREA IS CENTERED NEAR 30.5N 79.5W AT 10/0000 UTC OR 110 MILES SE OF SAVANNAH GEORGIA. ANDREA HAS BEEN MEANDERING DURING THE PAST FEW HOURS. 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. CONVECTION ASSOCIATED WITH THE RATHER LARGE SLOPPY CIRCULATION OF ANDREA HAS GENERALLY BEEN ON THE DECLINE FOR MUCH OF THE DAY...ESPECIALLY OVER THE NW QUADRANT. MOSAIC DOPPLER RADAR FROM THE SOUTHEAST SHOWS NARROW BROKEN BANDS OF SHOWERS AND ISOLATED TSTMS ONSHORE AND OVER THE COASTAL WATERS. HOWEVER...OVER THE PAST FEW HOURS AN IMPROVED WIDER BAND OF CONVECTION HAS TAKEN SHAPE IN THE ERN SEMICIRCLE. THE SYSTEM IS LOCATED IN WEAK STEERING AND HAS BEEN SLOWLY DRIFTING THROUGHOUT THE DAY. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 10N13W 7N22W 3N36W 1N51W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM EITHER SIDE OF THE AXIS BETWEEN 22W-29W. SIMILAR ACTIVITY LIES FROM THE EQ-2N BETWEEN 30W-39W. ...DISCUSSION... GULF OF MEXICO... DEEP LAYER NLY FLOW ON THE W SIDE OF ANDREA'S LARGE CIRCULATION IS ENHANCING SUBSIDENCE ABOVE THE ERN HALF OF THE GULF PROVIDING WIDESPREAD FAIR WEATHER. THE SMOKE PLUMES ORIGINATING FROM FIRES IN FLORIDA AND S GEORGIA HAVE NOW SPREAD BOTH TOWARD THE BAY OF CAMPECHE AND INTO THE WRN ATLC STEERED BY THE DIVERGENT LOW-LEVEL FLOW BETWEEN ANDREA AND WEAK HIGH PRES TO THE W. VISIBILITIES ARE MUCH IMPROVED ACROSS THE ERN GULF WATERS N OF 24N. HOWEVER...OBS FROM SE FLORIDA STILL SHOWED VISIBILITIES REDUCED TO THE 3-5 SM RANGE THIS AFTERNOON...BUT IT SHOULD IMPROVE THERE SHORTLY. THE WEAK HIGH PRES MENTIONED IS ANALYZED AT 1018 MB ABOUT 120 NM S OF THE LOUISIANA COAST NEAR 28N92W. THIS SYSTEM IS PRODUCING LIGHT NE/ELY WINDS W OF 89W AIDING IN THE TRANQUIL CONDITIONS. FAIRLY LIGHT WINDS AND MOSTLY FAIR WEATHER IS EXPECTED TO CONTINUE THROUGH FRI AS WEAK HIGH PRES REMAINS STATIONARY IN THE MID-GULF. CARIBBEAN SEA... THE CONTINUED WEAK PRES PATTERN IN THE WRN CARIB IS ALLOWING NE WINDS TO REMAIN VERY LIGHT...GENERALLY 10 KT OR LESS. THE TRADES INCREASE TO MORE TYPICAL VALUES IN THE CENTRAL AND ERN CARIB...15-20 KT...AS SFC RIDGING FROM THE N AND NE HAS BUILT INTO THE REGION. IN THE UPPER LEVELS...A DEEP TROUGH EXTENDS SWD FROM THE SUBTROPICAL STORM ACROSS ERN CUBA TO NEAR 14N75W. ABUNDANT SUBSIDENCE LIES ABOVE AND TO THE W OF THIS AXIS SUPPRESSING ANY DEEP CLOUD FORMATION. PRONOUNCED UPPER DIFFLUENCE TO THE E OF THE AXIS IS GENERATING A SWATH OF MOISTURE BETWEEN 67W-73W. DOPPLER RADAR FROM SAN JUAN PUERTO RICO SHOWS SCATTERED SHOWERS AND TSTMS IN ITS FAR NW RANGE WHICH MATCHES UP WITH SATELLITE IMAGERY...SO SCATTERED SHOWERS AND ISOLATED TSTMS ARE POSSIBLE IN THE AREA OUTLINED. ATLANTIC... SUBTROPICAL STORM ANDREA IS THE AREA OF FOCUS THIS EVENING...FOR DETAILS REFER TO THE SPECIAL FEATURE SECTION ABOVE. AN UPPER DIFFLUENT ZONE TO THE E OF ANDREA...BETWEEN THE STORM'S EMBEDDED TROUGH AND RIDGING TO THE E...IS GENERATING A SWATH OF SCATTERED SHOWERS AND ISOLATED TSTMS BETWEEN 65W-71W. A FEW SHIP OBSERVATIONS IN THE REGION INDICATE THAT THERE COULD BE A SFC TROUGH IN THIS AREA OF WEATHER. THIS MAY BE ADDED/BROUGHT BACK TO THE 00 Z SFC ANALYSIS IF THE DATA CONTINUES TO SUPPORT IT. FARTHER E...THE UPPER PATTERN FOLDS INTO A VERY BROAD TROUGH. EMBEDDED IN THIS TROUGH IS A WEAK 1016 MB LOW LOCATED NEAR 34N39W WITH A SFC TROUGH STRETCHING SW TO NEAR 26N52W. THE LAST FEW VIS SHOTS BEFORE DARKNESS INDICATE THAT THERE COULD BE ANOTHER WEAK LOW ON THE TROUGH AXIS NEAR 28N. REGARDLESS...THIS SYSTEM IS WEAK ONLY PRODUCING ISOLATED SHOWERS WITHIN 90 NM OF THE SFC BOUNDARY. MODERATE TO STRONG SFC HIGH PRES IS IN CONTROL BOTH TO THE E AND W OF THE LOW PRES TROUGH WITH ONE 1028 MB HIGH CENTERED IN THE CENTRAL ATLC NEAR 37N55W AND THE OTHER ANALYZED 1024 MB ABOUT 210 NM W OF PORTUGAL NEAR 38N13W. A FAIRLY DENSE SURGE OF SAHARAN DUST HAS PUSHED INTO THE ATLC WITH THE LEADING EDGE REACHING 25W. THINNER PATCHES OF DUST HAVE SPREAD FURTHER W INTO THE CENTRAL ATLC. THIS VERY DRY AIR HAS CLEARED MOST OF THE LOW TO MID LEVEL CLOUDS IN THE ERN-MOST ATLC. $$ CANGIALOSI