000 AXNT20 KNHC 290000 TWDAT TROPICAL WEATHER DISCUSSION... NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU AUG 28 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... TROPICAL STORM GUSTAV IS CENTERED NEAR 17.9N 77.0W AT 29/0000 UTC OR ABOUT 13 NM WEST OF KINGSTON JAMAICA AND ABOUT 260 NM EAST-SOUTHEAST OF GRAND CAYMAN MOVING WEST AT 6 KT. MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. PLEASE SEE THE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC AND/OR THE PUBLIC ADVISORY MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS. GUSTAV IS TRACKING OVER JAMAICA THIS EVENING AND IS FORECAST TO EMERGE OUT INTO THE OPEN WATERS OF THE NW CARIBBEAN BY TOMORROW. WITH A WEAK MID-LEVEL RIDGE OVER FLORIDA...ALL MODELS FORECAST GUSTAV TO CONTINUE GENERALLY WESTWARD FOR THE NEXT DAY OR SO AND COME UNDER THE INFLUENCE OF ANTICYCLONIC FLOW ALOFT WHICH ALONG WITH THE WARM WATERS WILL BE FAVORABLE FOR STRENGTHENING. MODERATE TO STRONG CONVECTION IS FROM 15N-20N BETWEEN 73W-79W INCLUDING JAMAICA. SIMILAR OUTER BANDS OF CONVECTION ARE ACROSS HISPANIOLA AND S OF CENTRAL CUBA BETWEEN 78W-81W. GUSTAV IS EXPECTED TO PRODUCE TOTAL RAINFALL ACCUMULATIONS OF 6 TO 12 INCHES ACROSS JAMAICA AND THE CAYMAN ISLANDS...WITH ISOLATED MAXIMUM AMOUNTS OF UP TO 25 INCHES POSSIBLE. THESE RAINS WILL LIKELY PRODUCE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. RAINFALL ACCUMULATIONS OF 2 TO 4 INCHES ARE POSSIBLE OVER SOUTHERN CUBA. RAINFALL WILL BE DIMINISHING OVER HAITI TONIGHT...WITH AN ADDITIONAL 1 TO 2 INCHES OF RAINFALL POSSIBLE. TROPICAL STORM HANNA IS CENTERED NEAR 20.7N 60.1W AT 28/2100 UTC OR ABOUT 225 NM NORTHEAST OF THE NORTHERN LEEWARD ISLANDS MOVING WEST-NORTHWEST AT 10KT. A TURN TOWARD THE NORTHWEST IS FORECAST OVER THE NEXT COUPLE OF DAYS WITH GRADUAL STRENGTHENING EXPECTED AS THE CYCLONE WILL MOVE AWAY FROM THE NORTHERN LEEWARD ISLANDS AND BE CENTERED WELL TO THE NORTHEAST OF THE BAHAMAS DURING THE NEXT COUPLE OF DAYS. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC AND/OR THE PUBLIC ADVISORY MIATCPAT3/WTNT33 KNHC FOR MORE DETAILS. HANNA IS INTERACTING WITH AN UPPER-LEVEL LOW TO THE WEST THAT IS PROVIDING A SHEARED ENVIRONMENT LIMITING ITS SHORT TERM INTENSIFICATION. THIS UPPER-LEVEL LOW IS FORECAST TO MOVE WESTWARD AND WILL PROVIDE HANNA WITH A MORE FAVORABLE ENVIRONMENT TO BECOME A HURRICANE IN ABOUT 72 HOURS OR SO. ...TROPICAL WAVES... A WELL-DEFINED TROPICAL WAVE IS LOCATED NEAR THE WEST COAST OF AFRICA EAST OF DAKAR SENEGAL AND IS EMERGING INTO THE EXTREME TROPICAL ERN ATLANTIC. IT WILL BE ADDED TO THE 29/0000 UTC SURFACE ANALYSIS. GRADUAL DEVELOPMENT OF THIS SYSTEM IS POSSIBLE DURING THE NEXT COUPLE OF DAYS AS IT MOVES WESTWARD AT ABOUT 10-15 KT. A BROAD CYCLONIC CIRCULATION IS OBSERVED WITH SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 11N-16N EAST OF 18W TO THE AFRICAN COAST. A TROPICAL WAVE IS ALONG 38W FROM 12N TO 21N WITH A 1009 MB LOW ALONG THE WAVE AXIS AT 17.5N MOVING W AT 10 KT. DEEP CONVECTION IS NEARLY VOID WITH ONLY SPARSE SCATTERED SHOWERS WITHIN 150 NM IN THE NRN SEMICIRCLE OF THE ASSOCIATED LOW PRESSURE. ANY DEVELOPMENT OF THIS SYSTEM DURING THE NEXT COUPLE OF DAYS WILL BE SLOW TO OCCUR. A TROPICAL WAVE IS ALONG 53W S OF 13N MOVING W NEAR 10-15 KT. A VERY WEAK LOW-LEVEL BROAD CYCLONIC TURNING IS OBSERVED ON SATELLITE IMAGERY BUT DEEP VERTICAL MOISTURE AND CONVECTION ARE ABSENT WITH THE WAVE. ...THE ITCZ... THE ITCZ AXIS IS ANALYZED ALONG 11N14W 10N19W 16N29W 16N35W 13N40W 8N51W 8N55W 8N61W. OTHER THAN CONVECTION ASSOCIATED WITH TROPICAL WAVE EMERGING OFF THE W AFRICAN COAST...CLUSTERS OF SCATTERED MODERATE CONVECTION IS WITHIN 150 NM OF A LINE FROM 7N18W TO 12N32W. ...DISCUSSION... GULF OF MEXICO... AN UPPER TROUGH DISSECTS THE GULF OF MEXICO FROM NW FLORIDA TO THE YUCATAN PENINSULA WHILE AN UPPER ANTICYCLONE IS CENTERED OVER THE NW CARIBBEAN SEA. DRY UPPER AIR IS NOTED N OF 24N TO THE W OF THE UPPER TROUGH...AND IS SUPPRESSING CONVECTION TO ONLY A FEW SHOWERS OVER THE S CENTRAL GULF. A WEAK SURFACE RIDGE ENCOMPASSES THE NRN GULF WATERS WHILE A 1008 MB LOW CENTERED OFFSHORE OF VERACRUZ MEXICO NEAR 19N96W IS TRIGGERING SCATTERED MODERATE TO STRONG CONVECTION ACROSS THE SW GULF FROM 21N-25N BETWEEN 92W-97W. ELSEWHERE SCATTERED SHOWERS AND THUNDERSTORMS ARE ACROSS THE CENTRAL FLORIDA PENINSULA IN ASSOCIATION WITH AN UPPER DIFFLUENT PATTERN LOCATED EAST OF THE UPPER TROUGH ACROSS THE CENTRAL GULF. CARIBBEAN SEA... AN UPPER TROUGH ENTERS THE CARIBBEAN SEA THROUGH THE MONA PASSAGE TO SOUTH OF JAMAICA. AN UPPER ANTICYCLONE IS CENTERED OVER THE NW CARIBBEAN. AN UPPER RIDGE EXTENDS SW OVER THE SE CARIBBEAN ALONG THE NRN COAST OF SOUTH AMERICA. TROPICAL STORM GUSTAV IS UNDER THE WRN EDGE OF THE UPPER TROUGH AXIS AND WILL CONTINUE MOVING W FURTHER AWAY FROM INFLUENCE OF LAND...AND EVENTUALLY UNDER THE INFLUENCE OF THE NW CARIBBEAN UPPER ANTICYCLONE...WHICH WILL PROVIDE FOR A MORE FAVORABLE ENVIRONMENT AND CONTINUED DEVELOPMENT. SCATTERED MODERATE TO STRONG CONVECTION IS ACROSS PANAMA EXTENDING 100 NM OFFSHORE IN THE FAR SW CARIBBEAN DUE TO THE PROXIMITY OF THE ITCZ. SIMILAR AREAS OF CONVECTION ARE ACROSS CENTRAL AMERICA FROM VILLAHERMOSA MEXICO SE TO CENTRAL NICARAGUA AND COSTA RICA. A FEW SCATTERED SHOWERS ARE ALSO NOTED OVER THE LESSER ANTILLES THIS EVENING. ATLANTIC OCEAN... A SERIES OF UPPER LEVEL FEATURES DOMINATE THE SUBTROPICAL N ATLANTIC. AN UPPER RIDGE EXTENDS NE FROM THE NW CARIBBEAN TO BEYOND 31N76W WITH CONVECTION ENHANCED ACROSS THE CENTRAL FLORIDA PENINSULA FROM FORT MYERS NE TO OVER THE W ATLC NEAR 29N80W. ANOTHER UPPER ANTICYCLONE IS NEAR 29N67W WITH A FEW SHOWERS NOTED ALONG THE NRN PERIPHERY OF A SURFACE TROUGH THAT EXTENDS FROM 24N73W TO 30N70W. A CUT-OFF UPPER LOW IS N OF PUERTO RICO CENTERED NEAR 22N66W GENERATING ISOLATED SHOWERS FROM 21N-25N BETWEEN 62W-66W AND OVER THE ERN GREATER ANTILLES INCLUDING PUERTO RICO AND THE VIRGIN ISLANDS. AN UPPER RIDGE LOCATED OVER T.S. HANNA IS PROVIDING GOOD OUTFLOW ALOFT MAINLY TO THE N AND E OF THE CYCLONE. A SECOND WEAKENING UPPER LOW IS OVER THE N/CENTRAL ATLC CENTERED NEAR 32N43W AND EXTENDS TROUGHING S TO 22N. AN E-W UPPER RIDGE COVERS THE ERN ATLC ALONG 24N TO 40W. AT THE SURFACE...A BROAD SURFACE RIDGE REMAINS OVER THE ATLC N OF 25N E OF 50W ANCHORED BY A 1028 MB HIGH W OF THE AZORES. $$ HUFFMAN