AXNT20 KNHC 250001 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...SPECIAL FEATURES... T.D. DOLLY IS DUMPING HEAVY RAINS AS IT MOVES FARTHER INLAND ALONG THE RIO GRANDE RIVER VALLEY. AT 24/2100 UTC...DOLLY WAS LOCATED NEAR 28.2N 100.6W...ABOUT 35 MILES...55 KM SOUTH OF EAGLE PASS TEXAS MOVING WEST-NORTHWEST AT 12 KT. ESTIMATED MINIMUM PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH HIGHER GUSTS. DISSIPATION OF THE SYSTEM IS EXPECTED IN A DAY OR SO. PLEASE SEE THE LAST 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 AND BROAD CIRCULATION ACCOMPANIED BY A FEW REMAINING CONVECTIVE BANDS MAINLY OVER INLAND SOUTH TEXAS. UPPER LEVEL MOISTURE/CLOUDINESS AND 10-20 KT SOUTHEASTERLY SURFACE WINDS REMAINS ACROSS THE WRN GULF THIS EVENING WITH CLEARING EXPECTED AS SURFACE HIGH PRESSURE REGAINS CONTROL OVER THE GULF OF MEXICO THIS WEEKEND. ...TROPICAL WAVES... A HIGH AMPLITUDE TROPICAL WAVE IS ALONG 35W/36W S OF 23N MOVING W NEAR 20 KT. VIS SATELLITE IMAGERY INDICATES A BROAD CYCLONIC CIRCULATION AND A 1010 MB LOW ALONG THE WAVE AXIS NEAR 14N. THIS LOW IS FORECAST BY THE COMPUTER MODELS TO MOVE WEST DURING THE NEXT 24-48 HOURS. SHOWER ACTIVITY REMAINS LIMITED AT THIS TIME FROM 17N-23N BETWEEN 32W-39W. THE WAVE SHOWS UP VERY WELL ON THE MIMIC-TPW PRODUCT FROM CIMSS WHERE A LARGE BULGE OF MOISTURE IS OBSERVED. TIGHT PRESSURE GRADIENT BETWEEN THE LOW AND THE ATLC SURFACE HIGH WILL PRODUCE AN INCREASE IN WINDS ACROSS THE CENTRAL ATLC THROUGH THE WEEKEND. A TROPICAL WAVE IS ALONG 59W/60W S OF 18N MOVING W NEAR 10-15 KT. WEAK INVERTED-V CURVATURE IS OBSERVED ON SATELLITE IMAGERY AND EXTENDS NORTHWARD TO NEAR SAINT LUCIA. THE WAVE IS BENEATH STRONG TO MODERATE SUBSIDENCE/DRY AIR ALOFT WITH SCATTERED MODERATE CONVECTION ACROSS NWRN GUYANA AND NERN VENEZUELA. LOW TOPPED SHOWERS ARE ALSO ACROSS THE WINDWARD ISLANDS S OF 13N. A TROPICAL WAVE IS OVER CENTRAL AMERICA AND THE GULF OF HONDURAS ALONG 86W S OF 17N MOVING W NEAR 10 KT. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE EAST OF THE WAVE AXIS AFFECTING THE SW CARIBBEAN AND THE ERN COASTS OF NICARAGUA/COSTA RICA. A DIFFLUENT PATTERN ALOFT OVER THE AREA IS AIDING IN ENHANCING THIS CONVECTIVE ACTIVITY. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 11N15W 8N19W 10N27W 10N33W 9N39W 6N54W. SCATTERED MODERATE TO STRONG CONVECTION IS ALONG THE W AFRICAN COAST FROM 10N-14N BETWEEN 13W-17W AND MAY BE ASSOCIATED WITH A NEW TROPICAL WAVE PROPAGATING OFF THE COAST. FURTHERMORE THE HOVMOLLER DIAGRAM HAS DEPICTED THE WESTWARD MOVEMENT OF THESE SHOWERS AND TSTMS OVER THE PAST COUPLE OF DAYS. SCATTERED MODERATE CONVECTION IS FROM 6N-11N BETWEEN 20W-26W. ...DISCUSSION... GULF OF MEXICO... BROAD UPPER LEVEL ANTICYCLONE ASSOCIATED WITH DOLLY AND CENTERED OVER THE SOUTHERN GREAT PLAINS EXTENDS A RIDGE ACROSS THE ENTIRE GULF OF MEXICO AND THE FLORIDA PENINSULA. THIS IS AIDING IN GENERATING SCATTERED SHOWERS WITH EMBEDDED TSTMS ACROSS SOUTHERN FLORIDA. MAINLY UPPER LEVEL MOISTURE/CLOUDINESS ARE OBSERVED IN THE WAKE OF DOLLY OVER THE WESTERN GULF. A FEW SCATTERED SHOWERS/TSTMS ARE ACROSS SRN MEXICO AND THE FAR ERN BAY OF CAMPECHE. AT THE SURFACE...THE ATLANTIC RIDGE EXTENDS WESTWARD AND ENVELOPS THE ERN GULF WITH A WEAK 1020 MB HIGH CENTERED NEAR 28N86W. LIGHT AND VARIABLE WINDS PREVAIL UNDER THE INFLUENCE OF THIS SYSTEM AND WILL CONTINUE TO BUILD ACROSS THE WRN GULF OVER THE WEEKEND. CARIBBEAN SEA... AN UPPER-LEVEL TROUGH EXTENDS FROM THE WRN ATLC S-SW INTO THE NW CARIBBEAN AND INTO THE GULF OF HONDURAS. THIS TROUGH IS GENERATING SCATTERED SHOWERS/TSTMS ACROSS WRN CUBA EXTENDING INTO ADJACENT NW CARIBBEAN COASTAL WATERS. THE REMAINDER OF THE BASIN IN UNDER THE INFLUENCE OF AN UPPER-LEVEL RIDGE ANCHORED ON AN ANTICYCLONE LOCATED OVER PUERTO RICO. S-SW FLOW BETWEEN THE ABOVE MENTIONED UPPER LEVEL FEATURES IS DRAWING SUFFICIENT UPPER LEVEL MOISTURE FROM THE E PACIFIC REGION INTO THE CARIBBEAN SEA ACROSS THE SW CARIBBEAN TO JAMAICA...ERN CUBA AND THE WINDWARD PASSAGE. THESE DIFFLUENT UPPER WINDS ARE ENHANCING SCATTERED MODERATE CONVECTION OVER PANAMA AND THE SW CARIBBEAN S OF 11N. MODERATE TO STRONG SUBSIDENCE DOMINATES THE ERN PORTION OF THE BASIN. A TROPICAL WAVE IS MOVING WESTWARD ACROSS CENTRAL AMERICA WITH A SECOND TROPICAL WAVE APPROACHING THE LESSER ANTILLES. 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 37N55W DOMINATES ALMOST THE ENTIRE FORECAST AREA. THIS SURFACE RIDGE WILL REMAIN IN PLACE 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 NW CARIBBEAN. A SURFACE TROUGH IS OVER THE WEST-CENTRAL ATLC AND NOW EXTENDS FROM 23N62W TO 31N61W. SATELLITE IMAGERY INDICATES THAT LOW LEVEL CLOUDS REMAIN ASSOCIATED WITH THIS TROUGH NEAR 29N. 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 SURFACE LOW ASSOCIATED WITH THE TROPICAL WAVE OVER THE ERN ATLC. $$ HUFFMAN