000 AXNT20 KNHC 110544 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SAT AUG 11 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...TROPICAL WAVES... HIGH AMPLITUDE TROPICAL WAVE IS JUST MOVING OUT OF THE AFRICAN COAST. IT AXIS IS ALONG 15W S OF 22N WITH A 1008 MB LOW PRES NEAR 13N. STRONG CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION ARE AHEAD OF THE WAVE AXIS COVERING FROM 10N-14N E OF 19W. SOME OF THE COMPUTER MODELS DEVELOP THIS LOW INTO A TROPICAL CYCLONE AS IT MOVES WWD ACROSS THE ATLANTIC OCEAN. TROPICAL WAVE IS ALONG 28W S OF 17N MOVING W 5-10 KT. THIS WEAK FEATURE HAS BEEN EMBEDDED IN VERY LIGHT STEERING OVER THE PAST 24 HOURS. IT IS EXPECTED TO SPEED UP SHORTLY AS AN ELY JET SETS UP IN THIS REGION. CURRENT SATELLITE IMAGES SHOW LITTLE WAVE SIGNATURE...SO THE CURRENT POSITION IS BASED ON SLOW FORWARD EXTRAPOLATION WHICH AGREES WELL WITH A NEARLY STATIONARY MOISTURE BUMP SEEN IN THE SSMI-DERIVED TOTAL PRECIPITABLE WATER. TROPICAL WAVE IS ALONG 44W S OF 14N MOVING W 10-15 KT. THIS LOW AMPLITUDE WAVE REMAINS WEAK CAUSING A VERY SLIGHT PERTURBATION IN THE ITCZ. SCATTERED SHOWERS ARE ASSOCIATED WITH THIS FEATURE. HIGH AMPLITUDE TROPICAL WAVE IS ALONG 67/68W S OF 21N MOVING W NEAR 15 KT. THIS WAVE WAS PREVIOUSLY ALONG 65W ON THE 00Z SFC MAP...BUT EARLIER QUIKSCAT PASS AND LATEST SFC DATA SHOW THAT THE WAVE AXIS IS FURTHER WEST ALONG THE MONA PASSAGE. THIS FEATURE IS GENERATING AN AREA OF SHOWERS WITH EMBEDDED TSTMS OVER DOMINICAN REPUBLIC AND THE REGIONAL COASTAL WATERS. THIS WAVE IS ALSO INTERACTING WITH AN UPPER LOW OVER THE BAHAMAS. THE SAN JUAN DOPPLER RADAR DEPICTS SCATTERED SHOWERS AND ISOLATED TSTMS BEHIND THE WAVE AXIS AFFECTING PUERTO RICO AND THE COASTAL WATERS. AS THE DAY GOES ON...MOISTURE FROM THIS WAVE SHOULD SPREAD FIRST OVER THE REMAINDER OF HISPANIOLA AND AFTERWARD OVER THE BAHAMAS AND EASTERN CUBA. TROPICAL WAVE IS ALONG 75W/76W S OF 19N MOVING W NEAR 15 KT. THIS WAVE IS PROBABLY ENHANCING SOME SHOWER ACTIVITY OVER EASTERN CUBA AND JAMAICA. THE SSMI-DERIVED TOTAL PRECIPITABLE WATER SHOW AN ENHANCED WWD MOVING MOISTURE SURGE IN AN ALREADY HIGH TPW ENVIRONMENT. THIS IS MAIN SOURCE USED TO TRACK THIS FEATURE. TROPICAL WAVE IS OVER THE YUCATAN PENINSULA AND GUATEMALA ALONG 90W/91W S OF 20N MOVING W 10-15 KT. THIS WAVE LIES UNDERNEATH AN UPPER LOW WHICH IS HELPING TO GENERATE SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 90 NM OF THE AXIS...PARTICULARLY OVER EL SALVADOR. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 10N17W 11N26W 11N36W 11N60W. CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION ARE JUST OFF THE AFRICAN COAST FROM 10N-14N E OF 19W...ASSOCIATED WITH A LARGE TROPICAL WAVE MAKING ITS WAY TO THE COAST. SCATTERED MODERATE CONVECTION IS NEAR 8N22W AND WITHIN 60 NM EITHER SIDE W OF 40W. DISCUSSION... GULF OF MEXICO... THE COMBINATION OF A STRONG UPPER HIGH OVER THE SRN U.S. AND AN UPPER LOW OVER THE SW CORNER OF THE GULF NEAR 21N94W CONTINUES TO PRODUCE STRONG UPPER E TO NE WIND FLOW ACROSS THE GULF. THE ATMOSPHERE HERE IS SLIGHTLY MORE MOIST THAN IT WAS OVER THE PAST FEW DAYS. SCATTERED SHOWERS ARE OVER THE SW GULF CAUSED BY INSTABILITY NEAR THE UPPER LOW AND A NEARBY TROPICAL WAVE. ISOLATED TO SCATTERED SHOWERS AND TSTMS ARE ALSO OVER THE SE GULF...S FLORIDA AND CUBA TRIGGERED BY A SFC TROUGH WHICH EXTENDS NWD FROM THE CARIB ACROSS W CUBA INTO SW FLORIDA. THE SFC PATTERN REMAINS WEAK WITH A QUASI-STATIONARY 1014 MB HIGH CENTER NEAR 28N93W. THIS WEAK PRES GRAD IS EXPECTED TO CONTINUE FOR A FEW MORE DAYS ALLOWING WINDS TO REMAIN LIGHT. THE UPPER LOW IS FORECAST TO MOVE WWD ACROSS CENTRAL MEXICO LATE TODAY. CARIBBEAN SEA... A CONSIDERABLE AMOUNT OF MOISTURE REMAINS OVER THE CARIBBEAN TONIGHT. SEVERAL UPPER LEVEL FEATURES ARE ENHANCING THIS MOISTURE. THEY ARE...THE UPPER LOW OVER THE SW GULF OF MEXICO...TWO UPPER HIGHS NEAR 19N83W AND 14N65W AND ANOTHER UPPER LOW NEAR THE CENTRAL BAHAMAS BAHAMAS. WITHIN THIS MOIST UPPER ENVIRONMENT THERE ARE TWO TROPICAL WAVES AND A SFC TROUGH HELPING TO PROVIDE EVEN MORE LIFT. SCATTERED SHOWERS AND TSTMS ARE AFFECTING ALL THE GREATER ANTILLES. SIMILAR SHOWER ACTIVITY IS SEEN OVER THE FAR SE CARIBBEAN AND OVER PARTS OF CENTRAL AMERICA DUE TO THE PASSAGE OF A TROPICAL WAVE CURRENTLY LOCATED OVER THE YUCATAN PENINSULA AND GUATEMALA. LIGHT TO MODERATE WINDS ARE FOUND IN THE WRN PORTION OF THE BASIN AND MODERATE TO FRESH TRADE WINDS IN THE E AND CENTRAL CARIB. ATLANTIC OCEAN... UPPER DIFFLUENCE BETWEEN AN UPPER LOW NEAR THE CENTRAL BAHAMAS AND AN UPPER HIGH OVER THE E CARIB IS SUPPORTING AN AREA OF SHOWERS AND TSTMS OVER THE SW ATLC NEAR THE SE BAHAMAS AND HISPANIOLA. FURTHER E...AN UPPER TROUGH EXTENDS SW ACROSS THE CENTRAL ATLC FROM AN UPPER LOW LOCATED NEAR 27N43W. RIDGING COVERS THE REMAINDER OF THE ATLC STRETCHING W FROM AN UPPER HIGH LOCATED NEAR MIDWAY BETWEEN THE CANARY AND CAPE VERDE ISLANDS. THERE IS LITTLE MOISTURE ASSOCIATED WITH EITHER THE RIDGE OR TROUGH. WV IMAGERY SHOWS ABUNDANT DRY AIR/SUBSIDENCE ALOFT E OF 50W...ALLOWING FAIR WEATHER TO PREVAIL. AT THE SFC...THE MAIN WEATHER FEATURE IS A STATIONARY 1025 MB HIGH CENTERED NEAR 36N34W. THIS HIGH EXTENDS A RIDGE SW REACHING THE NE CARIBBEAN AND THE BAHAMAS. IT IS PRODUCING LIGHT TO MODERATE TRADES ACROSS THE BULK OF THE ATLC DISCUSSION AREA. $$ GR