000 AXNT20 KNHC 120557 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT TUE AUG 12 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...SPECIAL FEATURES... A TROPICAL WAVE LOCATED OVER THE CENTRAL ATLANTIC ALONG 49W/50W OR ABOUT 650 NM EAST OF THE LESSER ANTILLES IS SUPPORTING AN AREA OF ORGANIZED SCATTERED SHOWERS AND THUNDERSTORMS FROM 14N-19N BETWEEN 46W-53W. A 1007 MB LOW IS EMBEDDED ON THE WAVE AXIS NEAR 13N. CONVECTIVE ACTIVITY HAS BEEN COME BETTER ORGANIZED OVER THE PAST 6-12 HOURS AND ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE FOR GRADUAL DEVELOPMENT OF THE SYSTEM WHICH HAS THE POTENTIAL TO BECOME A TROPICAL DEPRESSION DURING THE NEXT COUPLE OF DAYS AS IT MOVES WEST-NORTHWESTWARD AT 15 KT. A 1009 MB BROAD LOW PRESSURE AREA IS LOCATED OVER THE EASTERN ATLANTIC NEAR 12N30W. SATELLITE IMAGERY SHOWS INDICATIONS OF BETTER ORGANIZATION DURING THE PAST 12 HOURS. A LARGE AREA OF SCATTERED SHOWERS AND THUNDERSTORMS ACCOMPANIES THIS LOW FROM 8N-15N BETWEEN 26W-34W WHICH REMAINS EMBEDDED WITHIN THE ITCZ. A TROPICAL DEPRESSION COULD FORM WITHIN THIS AREA DURING THE NEXT DAY OR TWO AS IT MOVES WESTWARD AT ABOUT 10 KT. ...TROPICAL WAVES... A TROPICAL WAVE IS ACROSS THE CAPE VERDE ISLANDS. ITS AXIS IS ALONG 24W S OF 18N MOVING W NEAR 10 KT. BROAD CYCLONIC TURNING IS SEEN ALONG THE WAVE AXIS NEAR 13N. SCATTERED MODERATE CONVECTION IS OBSERVED MAINLY AHEAD OF THE WAVE FROM 12N-16N BETWEEN 25W-29W. A TROPICAL WAVE IS ALONG 73W S OF 19N MOVING W 15-20 KT. A WEAK INVERTED-V PATTERN IS SEEN ON SATELLITE IMAGERY. THE MIMIC-TPW SHOWS THAT MOISTURE ASSOCIATED WITH THIS FEATURE HAS SPLIT IN TWO PIECES. ONE REMAINS OVER THE CARIBBEAN SEA SOUTH OF HISPANIOLA WHILE THE SECOND ONE IS MOVING NWD OVER THE W ATLC. SCATTERED MODERATE CONVECTION IS FROM 9N-14N BETWEEN 72W-75W. A SURGE OF AFRICAN DUST CONTINUES TO FOLLOWS THIS WAVE AS SEEN FROM THE SAHARAN AIR LAYER PRODUCT FROM CIMSS. A TROPICAL WAVE EXTENDS FROM WRN CUBA TO PANAMA ALONG 83W MOVING W NEAR 15-20 KT. DEEP CONVECTION ASSOCIATED WITH THIS WAVE HAS WANED OVER THE PAST 6 HOURS WITH ONLY SCATTERED SHOWERS COVERING THE SW CARIBBEAN S OF 15N W OF 77W. MOISTURE WILL CONTINUE TO SPREAD OVER CENTRAL AMERICA THROUGH WED INCREASING THE CHANCE OF PRECIPITATION PARTICULARLY IN NICARAGUA...HONDURAS AND COSTA RICA. A DIFFLUENT PATTERN ALOFT IS CONTINUING TO PROMOTE CONVECTIVE DEVELOPMENT OVER THIS REGION. ...THE ITCZ... THE ITCZ IS CENTERED ALONG 15N17W 13N23W 12N27W 11N32W 13N42W 13N48W 12N51W 6N58W. OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE TWO TROPICAL WAVES AND THE LOW NEAR 12N30W...SCATTERED MODERATE CONVECTION IS FROM 6N-8N BETWEEN 34W-40W. ...DISCUSSION... GULF OF MEXICO... AN UPPER-LEVEL HIGH CENTERED OVER NE MEXICO EXTENDS RIDGING OVER A MAJORITY OF THE GULF. MULTILAYERED CLOUDINESS IS RIDING AROUND THIS RIDGE SEWD OFF THE SE CONUS AND RESIDES ACROSS THE NRN GULF N OF 26N. THE GULF REMAINS RATHER TRANQUIL TONIGHT WITH A SURFACE RIDGE ANCHORED ON A 1016 MB HIGH OVER THE SE GULF NEAR 25N86W. THE SURFACE CIRCULATION AROUND THIS HIGH IS PROVIDING THE WRN AND CENTRAL GULF WITH LIGHT TO MODERATE SOUTHERLY RETURN FLOW. THESE WINDS ARE EXPECTED TO GRADUALLY INCREASE THROUGH WED AND PERSIST AS A LOW PRESSURE SYSTEM DEVELOPS OVER TEXAS AND NE MEXICO AND SKIRTS EWD ALONG THE N GULF COAST. CARIBBEAN SEA... UPPER LEVEL TROUGHING EXTENDS FROM THE W ATLC THROUGH THE BAHAMAS AND ERN CUBA TO AN UPPER LEVEL LOW LOCATED NORTH OF PUERTO RICO NEAR 19N67W. THE REMAINDER OF THE CARIBBEAN IS UNDER THE INFLUENCE OF AN UPPER LEVEL HIGH CENTERED OVER NRN COLOMBIA NEAR 12N72W. UPPER DIFFLUENCE REMAINS ACROSS THE CARIBBEAN W OF 70W AND IS SUPPORTING AN AREA OF SCATTERED SHOWERS WITH EMBEDDED TSTMS FROM 8N-15N BETWEEN 71W-76W. A SIMILAR AREA OF SHOWERS IS WITHIN 120 NM OF THE WRN PANAMA AND COSTA RICA COASTLINE IN THE SW CARIBBEAN. ABUNDANT MIDDLE TO UPPER LEVEL CLOUDINESS AND MOISTURE IS NOTED OVER THE WRN CARIBBEAN S OF 19N AND W OF 70W. MODERATE TO STRONG SUBSIDENCE AND DRY AIR IS OVER THE ERN CARIBBEAN WITH PATCHES OF SHALLOW MOISTURE CROSSING THE WINDWARD ISLANDS. LIGHT TO MODERATE EASTERLY TRADE WINDS ARE OBSERVED ACROSS THE BASIN WITH THE STRONGEST WINDS OFFSHORE OF THE NRN COLOMBIAN COAST. TWO TROPICAL WAVES ARE MOVING WWD ACROSS WRN PORTIONS OF THE BASIN...SEE TROPICAL WAVE SECTION FOR MORE DETAILS. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH IS LOCATED OFF THE ERN U.S. SEABOARD AND REACHES INTO THE W ATLC. AN UPPER-LEVEL RIDGE IS TO THE SE CENTERED NEAR 30N64W. UPPER DIFFLUENCE BETWEEN THIS HIGH AND THE UPPER TROUGH IS PRODUCING A 250 NM WIDE BAND OF SHOWERS AND TSTMS FROM THE NW BAHAMAS TO BEYOND 32N70W. THIS ACTIVITY IS ALSO ASSOCIATED WITH THE REMNANTS OF A FRONTAL BOUNDARY. MOST CONCENTRATED AREA OF SCATTERED MODERATE CONVECTION IS FROM 27N-32N BETWEEN 64W-73W. ANOTHER UPPER LOW IS CENTERED NORTH OF PUERTO RICO NEAR 19N67W AND IS PRODUCING LITTLE SENSIBLE WEATHER. ELSEWHERE AN UPPER LOW IS OVER THE CENTRAL ATLC NEAR 28N52W WITH ANOTHER WEAK UPPER-LEVEL LOW OVER THE ERN ATLC NEAR 29N32W. AN UPPER-LEVEL HIGH IS LOCATED NEAR 22N25W...AND A STRONGER ONE IS CENTERED NEAR 18N43W WITH THE RIDGE COVERING THE DEEP TROPICS. THESE UPPER SYSTEMS ARE ENHANCING CONVECTION ALONG THE ITCZ. OTHERWISE...THE ATLANTIC FORECAST AREA IS DOMINATED BY A 1024 MB SURFACE HIGH CENTERED NEAR 35N48W. THIS HIGH EXTENDS A RIDGE SW TO CUBA AND THE SE GULF AND IS FORECAST TO MOVE NEWD DURING THE NEXT 24 HOURS OR SO. $$ HUFFMAN