000 AXNT20 KNHC 241757 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU JUL 24 2008 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND 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 FEATURES... T.S. DOLLY IS DUMPING HEAVY RAINS AS IT MOVES FARTHER INLAND OVER THE DEEP SOUTH AND THE NE PORTION OF MEXICO. AT 24/1800 UTC...IT IS LOCATED NEAR 27.9N 99.8W VERY NEAR THE U.S./MEXICO BORDER...ABOUT 25 NM...50 KM NW OF LAREDO TEXAS. ESTIMATED MINIMUM PRESSURE IS 998 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH HIGHER GUSTS. WEAKENING IS FORECAST DURING THE NEXT 24 HOURS. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS. DOPPLER RADAR AND SURFACE DATA INDICATE THAT DOLLY STILL HAS A LARGE CIRCULATION ACCOMPANIED BY NUMEROUS CONVECTIVE BANDS. THE MOST PROMINENT CONVECTION IS TO THE SOUTHEAST OF THE CENTER. DOLLY IS EXPECTED TO PRODUCE TOTAL RAINFALL ACCUMULATIONS OF 8 TO 12 INCHES...WITH ISOLATED AMOUNTS OF 20 INCHES...OVER PORTIONS OF SOUTH TEXAS AND NORTHEASTERN MEXICO. THESE RAINS ARE VERY LIKELY TO CAUSE WIDESPREAD FLOODING. ISOLATED TORNADOES ARE ALSO POSSIBLE OVER SOUTH CENTRAL TEXAS THE REST OF TODAY. ...TROPICAL WAVES... A HIGH AMPLITUDE TROPICAL WAVE IS ALONG 34W S OF 23N MOVING W NEAR 20 KT. VIS SATELLITE IMAGERY INDICATES A BROAD CYCLONIC CIRCULATION AND A 1012 MB LOW IS ADDED ALONG THE WAVE AXIS NEAR 14N. THIS LOW IS FORECAST BY THE COMPUTER MODELS TO MOVE WNW DURING THE NEXT 24-48 HOURS. SHOWER ACTIVITY IS VERY LIMITED AT THIS TIME AND SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED DURING THE NEXT COUPLE OF DAYS. THE WAVE SHOWS UP VERY WELL ON THE MIMIC-TPW PRODUCT FROM CIMSS WHERE A LARGE BULGE OF MOISTURE IS OBSERVED. IN ADDITION...THE 850 MB RELATIVE VORTICITY ALSO SUPPORTS THE PRESENCE OF THIS SFC LOW. TIGHT PRES GRADIENT BETWEEN THE LOW AND THE ATLC SFC HIGH WILL PRODUCE SOME INCREASE IN WINDS ACROSS THE CENTRAL ATLC DURING THE UPCOMING WEEKEND. A TROPICAL WAVE IS ALONG 58W S OF 18N MOVING W NEAR 10 KT. WEAK INVERTED-V CURVATURE IS OBSERVED ON SATELLITE IMAGERY. THE WAVE IS BENEATH STRONG TO MODERATE SUBSIDENCE/DRY AIR ALOFT WITH SCATTERED SHOWER ACTIVITY ACROSS GUYANA. LOW TOP SHOWERS ARE ALSO OCCURRING NEAR THE NORTHERN END OF THE WAVE AXIS. A TROPICAL WAVE IS OVER CENTRAL AMERICA ALONG 84W/85W S OF 17N MOVING W NEAR 10 KT. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE BEHIND THE WAVE AXIS AFFECTING THE SW CARIBBEAN AND THE ATLC COAST OF NICARAGUA. A DIFFLUENT PATTERN ALOFT OVER THE AREA IS ALSO ENHANCING THIS CONVECTIVE ACTIVITY. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 10N14W 11N25W 7N36W 5N46W 7N57W. A LARGE CLUSTER OF MODERATE TO STRONG CONVECTION HAS MOVED OFF THE AFRICAN COAST AND NOW COVERS THE AREA FROM 8N-12N BETWEEN 17W-21.5W. THIS CONVECTIVE ACTIVITY IS LIKELY ASSOCIATED WITH A NEW TROPICAL WAVE. THE VERTICAL SOUNDING FROM DAKAR THIS MORNING SHOWED NLY WINDS AT LOW LEVELS INDICATING THAT THE WAVE HAS NOT CROSS THIS AREA YET. THE HOVMOLLER DIAGRAM DEPICTS THE WWD PROPAGATION OF THIS AREA OF SHOWERS AND TSTMS OVER WESTERN AFRICA AND COASTAL WATERS. WE WILL WAIT FOR FURTHER DATA BEFORE PLACING THE WAVE AXIS. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N OF AXIS BETWEEN 35W-55W. ...DISCUSSION... GULF OF MEXICO... DOLLY...THE FOURTH TROPICAL CYCLONE OF THE 2008 HURRICANE SEASON MADE LANDFALL YESTERDAY ON SOUTH PADRE ISLAND TEXAS. TODAY...IN THE TROPICAL STORM STATUS CONTINUES TO DUMP HEAVY RAIN OVER SOUTH TEXAS AND NE MEXICO...SO A SIGNIFICANT POTENTIAL FOR INLAND FLOODING CONTINUES. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS. BROAD UPPER LEVEL ANTICYCLONE ASSOCIATED WITH DOLLY EXTENDS A RIDGE ACROSS THE ENTIRE GULF AND THE FLORIDA PENINSULA. THIS IS AIDING IN GENERATING SCATTERED SHOWER WITH EMBEDDED TSTMS ACROSS THE NE GULF WATERS NEAR THE FLORIDA BIG BEND REGION. AS OF 1500Z...A SFC TROUGH IS ANALYZED ACROSS THIS AREA AND GOES FROM 30N83W TO 25N85W. MAINLY HIGH CLOUDS ARE SEEN OVER THE WESTERN GULF. AT THE SURFACE...THE ATLANTIC RIDGE EXTENDS WESTWARD AND ENVELOPS THE ERN GULF WITH A WEAK 1019 MB HIGH CENTERED NEAR 28N87W. LIGHT AND VARIABLE WINDS PREVAIL UNDER THE INFLUENCE OF THIS SYSTEM. HIGH PRES WILL CONTINUE TO BUILD OVER NRN GULF WATERS THROUGH SUN. CARIBBEAN SEA... UPPER-LEVEL NORTHERLY WINDS ASSOCIATED WITH DOLLY'S OUTFLOW COVERS THE NW CARIBBEAN AND THE YUCATAN PENINSULA WHILE AN UPPER TROUGH EXTENDS FROM THE W ATLC ALL THE WAY SOUTH INTO THE CARIBBEAN TO THE GULF OF HONDURAS. THE REMAINDER OF THE BASIN IN UNDER THE INFLUENCE OF AN UPPER-LEVEL RIDGE ANCHORED ON A HIGH LOCATED JUST OVER PUERTO RICO. S-SW FLOW BETWEEN THE ABOVE MENTIONED UPPER LEVEL FEATURES IS DRAWING SUFFICIENT UPPER LEVEL MOISTURE FROM NRN SOUTH AMERICA INTO THE CARIBBEAN SEA ACROSS JAMAICA AND EASTERN CUBA. HISPANIOLA. THESE WINDS ARE ALSO ENHANCING CONVECTION OVER PANAMA AND THE SW CARIBBEAN. MODERATE TO STRONG SUBSIDENCE DOMINATES THE E PORTION OF THE BASIN. A TROPICAL WAVE IS MOVING WESTWARD ACROSS CENTRAL AMERICA. A SECOND ONE IS APPROACHING THE LESSER ANTILLES AND WILL MOVE INTO THE E CARIBBEAN TOMORROW. SEE TROPICAL WAVE SECTION FOR DETAILS. MODERATE TO STRONG TRADE WINDS ARE ACROSS THE AREA WITH THE STRONGEST WINDS JUST OFF THE COLOMBIAN COAST. ATLANTIC OCEAN... A 1030 MB HIGH LOCATED NEAR 36N54W DOMINATES ALMOST THE ENTIRE FORECAST AREA. THIS SYSTEM WILL SLIGHTLY STRENGTHEN DURING THE NEXT FEW DAYS PRODUCING MODERATE TO STRONG TRADE WINDS ACROSS THE TROPICS. BROAD AREA OF UPPER TROUGHING COVERS THE WRN ATLC AND EXTENDS S INTO THE WESTERN CARIBBEAN. A SFC TROUGH PERSISTS OVER THE W-CENTRAL ATLC AND NOW EXTENDS ALONG 59W/60W N OF 22N. VIS SATELLITE IMAGERY INDICATES THAT A SWIRL OF LOW LEVEL CLOUDS REMAINS ASSOCIATED WITH THIS TROUGH NEAR 28N. LIGHTNING DATA DEPICTS ISOLATED TSTMS NEAR THE NORTHERN END OF THE TROUGH. THE REMAINDER OF THE ATLANTIC OCEAN IS DOMINATED BY BENIGN UPPER LEVEL FEATURES WHERE STRONG SUBSIDENCE AND A DRY STABLE ATMOSPHERE ARE IN PLACE...PARTICULARLY BETWEEN 40W-65W. A LARGE AREA OF STRATOCUMULUS CLOUDS IS WRAPPING AROUND THE SFC LOW ASSOCIATED WITH THE TROPICAL WAVE OVER THE FAR ERN ATLC. $$ GR