000 AXNT20 KNHC 101739 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU MAY 10 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... ANDREA HAS BEEN DOWNGRADED TO A SUBTROPICAL DEPRESSION. AT 10/1500 UTC...THE CENTER OF NEWLY DOWNGRADED ANDREA WAS LOCATED NEAR 29.9N 79.9W OR ABOUT 100 MILES E OF JACKSONVILLE FLORIDA AND 80 MILES NE OF DAYTONA BEACH FLORIDA. ANDREA IS GENERALLY DRIFTING SOUTHWARD AND THIS SLOW MOTION IS EXPECTED OVER THE NEXT 24 HOURS. ESTIMATED MINIMUM CENTRAL PRESSURE REPORTED BY THE AIR FORCE PLANE IS 1003 MB. MAXIMUM SUSTAINED WINDS ARE NOW 30 KT WITH GUSTS TO 40 KT. CONTINUED GRADUAL WEAKENING IS EXPECTED DURING THE NEXT 24 HOURS. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/ WTNT21 KNHC FOR MORE DETAILS. MOSAIC DOPPLER RADAR FROM THE SE AND IR IMAGERY CLEARLY SHOWS THE ANDREA IS STRUGGLING TODAY MAINTAINING LITTLE CONVECTION WHICH IS MOSTLY CONFINED TO THE NE QUADRANT. NWLY SHEAR AND DRY AIR EVIDENT ON WATER VAPOR IMAGERY ALONG WITH RELATIVELY COOL SST'S ARE LIKELY THE CULPRITS FAVORING WEAKENING OF THE SUBTROPICAL SYSTEM. A GENERAL SLOW SWD MOTION AND SPIN DOWN TO A REMNANT LOW IS FORECAST OVER THE NEXT 24-48 HOURS. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 7N11W 4N25W 3N34W 2N45W EQ50W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 180 NM N AND 120 NM S OF THE AXIS BETWEEN 18W-28W. SCATTERED SHOWERS AND TSTMS LIE ELSEWHERE WITHIN 120 NM OF AXIS. ...DISCUSSION... GULF OF MEXICO... DEEP LAYER N TO NW FLOW ON THE W SIDE OF ANDREA IS ENHANCING SUBSIDENCE ABOVE THE ERN HALF OF THE GULF PROVIDING WIDESPREAD CLEAR SKIES AND FAIR WEATHER. MOST OF THE SMOKE PLUMES ORIGINATING FROM FIRES IN FLORIDA AND S GEORGIA APPEAR TO HAVE THINNED OUT ACCORDING TO THE LATEST VIS IMAGERY. HOWEVER...THERE IS STILL PROBABLY SOME AREAS OF REDUCED VISIBILITY ESPECIALLY IN THE NE GULF. A WEAK 1017 MB SFC HIGH PRES IS CENTERED ABOUT 180 NM S OF THE LOUISIANA COAST NEAR 27N92W. THE ASSOCIATED WEAK PRES PATTERN IS PRODUCING LIGHT ANTICYCLONIC FLOW AROUND THIS FEATURE AIDING IN THE TRANQUIL CONDITIONS. SEAS ARE ALSO OF LITTLE CONCERN WITH MOST BUOYS/SHIPS NOW IN THE 1-3 FT RANGE. FAIRLY LIGHT WINDS AND MOSTLY FAIR WEATHER IS EXPECTED TO CONTINUE THROUGH FRI AS WEAK HIGH PRES REMAINS STATIONARY IN THE MID-GULF...THOUGH SCATTERED SHOWERS/TSTMS ARE POSSIBLE IN THE NW PORTION AS THE UPPER LOW CURRENTLY OVER N TEXAS APPROACHES THE REGION. CARIBBEAN SEA... LOW PRES TO THE N OF THE AREA ASSOCIATED WITH ANDREA ALONG WITH A WEAK SFC TROUGH ALONG 79W N OF 15N IS ALLOWING WINDS TO BE VERY LIGHT ACROSS THE W CARIB...GENERALLY NE 10 KT OR LESS. TRADES INCREASE TO MORE TYPICAL VALUES...15-20 KT...AND VEER ELY TO THE E OF THE TROUGH AS SFC RIDGING HAS BUILT INTO THE REGION FROM THE NE. OVERALL...LITTLE CHANGE IS EXPECTED IN THIS SFC FLOW PATTERN OVER THE NEXT DAY OR TWO. IN THE MID AND UPPER LEVELS...THE PATTERN IS WNW TO ZONAL W OF 75W AND THEN BECOMES SWLY E OF THERE IN RESPONSE TO A PRONOUNCED RIDGE OVER THE CENTRAL ATLC. THE SWLY FLOW IS TRANSPORTING DEBRIS BROKEN HIGH LEVEL CLOUDS FROM THE ITCZ ACROSS THE GREATER ANTILLES...ROUGHLY BETWEEN 65W-77W. THERE COULD BE A FEW POCKETS OF DEEP MOISTURE EMBEDDED IN THIS HIGH LEVEL MOISTURE PLUME BUT IT APPEARS VERY ISOLATED IN NATURE. LITTLE CHANGE IN MOISTURE IS ANTICIPATED THRU FRI AS THE UPPER PATTERN HOLDS. ATLANTIC... A LARGE UPPER TROUGH...IN WHICH SUBTROPICAL DEPRESSION ANDREA IS EMBEDDED WITHIN...COVERS MUCH OF THE W ATLC. UPPER CONFLUENCE TO THE S OF THE SYSTEM IS ENHANCING SUBSIDENCE W OF 73W. A NARROW STRONG RIDGE LIES TO THE E OF THIS TROUGH WITH THE AXIS RUNNING FAIRLY N-S ALONG 57W. UPPER DIFFLUENCE BETWEEN THESE FEATURES AND LOW-LEVEL CONVERGENCE NEAR A DEVELOPING SFC TROUGH IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS BETWEEN 60W-70W...MOST ORGANIZED N OF 23N. AT THE SFC...WINDS ARE GENERALLY OUT OF THE E TO SE BETWEEN ANDREA AND A 1028 MB HIGH NEAR 37N50W. SHIPS/BUOYS AND THIS MORNING'S QSCAT PASS INDICATE THAT THE WINDS ARE FAIRLY LIGHT...10-15 KT ACROSS MOST OF THE AREA...WITH THE EXCEPTION BEING CLOSER TO ANDREA'S CENTER. REFER TO THE SPECIAL FEATURE SECTION FOR MORE DETAILS ON ANDREA. FARTHER E...A VERTICALLY STACKED LOW PRES SYSTEM AND ITS ASSOCIATED BROAD UPPER TROUGHING IS THE GENERAL MID/UPPER PATTERN THEME. THE SFC LOW IS ANALYZED VERY WEAK...1020 MB DUE TO ITS HIGH PRES ENVIRONMENT...NEAR 32N41W WITH A TROUGH HANGING SW TO 29N53W. LOW-MID LEVEL CLOUDS AND ISOLATED SHOWERS ARE POSSIBLE WITHIN 60 NM OF THE TROUGH AXIS. A MORE ORGANIZED SWATH OF MOISTURE LIES A COUPLE HUNDRED NM TO THE S...NAMELY FROM 21N-26N BETWEEN 35W-42W. THIS ACTIVITY IS ASSOCIATED WITH UPPER DIFFLUENCE TO THE E OF THE UPPER LOW CENTER WHICH IS LOCATED NEAR 26N43W. ELSEWHERE...A 1026 MB SFC HIGH CENTERED NEAR 36N14W IS IN CONTROL GENERATING A LARGE AREA OF MODERATE TRADES. ANOTHER VERY NOTICEABLE FEATURE IN THE E ATLC IS THE DENSE SAHARAN DUST WITH THE LEADING EDGE REACHING ABOUT 30W ACCORDING TO THE UW-CIMSS SAL ANALYSIS AND THE HAZY LOOK ON VIS IMAGERY. THIS VERY DRY AIR HAS ERODED ALL OF THE CLOUD COVER IN THE LOW TO MID LAYER OF THE ATMOSPHERE. $$ CANGIALOSI