000 AXNT20 KNHC 111804 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST SUN NOV 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 59W/60W S OF 13N MOVING W NEAR 20 KT. VIS SATELLITE IMAGERY AND THE SAHARAN AIR LAYER PRODUCT FROM CIMSS CLEARLY SHOWS A LARGE SURGE OF AFRICAN DUST ACCOMPANYING THIS WAVE. THE LESSER ANTILLES...BETWEEN GUADELOUPE AND GRENADA ARE REPORTING DUST AND HAZE. THE LEADING EDGE OF THIS DRY/STABLE AIR MASS IS REACHING THE EASTERN CARIBBEAN. THE WAVE IS GENERATING SOME SHOWER ACTIVITY OVER THE ISLANDS OF TRINIDAD AND TOBAGO AS WELL AS INLAND OVER GUYANA. TROPICAL WAVE IS ALONG 69W S OF 14N MOVING W NEAR 10 KT. THIS WAVE IS ALSO PRODUCING SOME SHOWER ACTIVITY OVER THE ABC ISLANDS AND REGIONAL WATERS. BONAIRE HAS REPORTED GUSTY WINDS UP TO 25 KT AND RAIN SHOWER WITH THE PASSAGE OF THE WAVE. ...THE ITCZ... THE ITCZ IS PRETTY ACTIVE TODAY. IT AXIS IS CENTERED ALONG 8N13W 6N25W 7N40W 6N56W. SCATTERED MODERATE/STRONG CONVECTION COVERS THE AREA FROM 3N-9N EAST OF 34W. IT APPEARS THAT A SFC TROUGH OR TROPICAL WAVE IS UNDERNEATH OF CONVECTION NEAR 30W. THE GFS MODEL IS SHOWING A WWD PROPAGATION OF A WIND SHIFT MOST LIKELY ASSOCIATED WITH THE FUTURE PROGRESS OF THE TROUGH OR TROPICAL WAVE. DISCUSSION... GULF OF MEXICO... THE ENTIRE GULF CONTINUES UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED ON A HIGH LOCATED OVER THE CAROLINAS. ONLY PATCHES OF LOW/MID CLOUDS WITH ISOLATED SHOWERS ARE SEEN OVER THE AREA. THIS RIDGE IS FORECAST BY THE COMPUTER MODELS TO PERSIST DURING THE NEXT SEVERAL DAYS. MID/UPPER LEVEL NWLY FLOW BETWEEN A RIDGE ALONG THE E COAST OF MEXICO AND AN UPPER TROUGH OVER THE W ATLC DOMINATES THE REGION WITH DRY/SUBSIDENCE AIR. SE RETURN FLOW OF 15 TO 20 KT...ON THE WESTERN PERIPHERY OF THE RIDGE ARE BLOWING ACROSS THE NW PORTION OF THE GULF...BUT ARE EXPECTED TO DIMINISH TONIGHT. CARIBBEAN SEA... ATTENTION REMAINS FOCUSED ON AN ELONGATED AREA OF CLOUDINESS... SHOWERS...AND THUNDERSTORMS OVER THE SOUTHWESTERN CARIBBEAN SEA. THIS ACTIVITY IS ASSOCIATED WITH A 1008 MB LOW PRESSURE NEAR 11N81W OR ABOUT 85 NM EAST OF SOUTHERN NICARAGUA...MOVING WWD NEAR 10 KT. ALTHOUGH THIS SYSTEM HAS BECOME A LITTLE BETTER ORGANIZED THIS MORNING...ADDITIONAL DEVELOPMENT IS EXPECTED TO BE LIMITED BEFORE THE LOW MOVES INLAND OVER CENTRAL AMERICA WITHIN THE NEXT 12 TO 24 HOURS. THE MOST SIGNIFICANT IMPACT WITH THIS SYSTEM WILL BE THE POTENTIAL FOR LOCALLY HEAVY RAIN OVER PORTIONS OF NICARAGUA AND COSTA RICA. SATELLITE PICTURES INDICATES THAT THE LEADING EDGE OF THIS CONVECTIVE ACTIVITY IS JUST MOVING ONSHORE OVER THE CARIBBEAN PLAINS OF NICARAGUA AND NORTHERN COSTA RICA. A SFC TROUGH EXTENDS FROM THIS LOW TO NEAR WESTERN JAMAICA. SCATTERED SHOWERS AND TSTMS ARE WITHIN 180 NM SE OF TROUGH AFFECTING JAMAICA AND COASTAL WATERS. IN ADDITION TO LOW LEVEL CONVERGENCE NEAR THE LOW/TROUGH...A DIFFLUENT PATTERN ALOFT IS HELPING TO DEVELOP THIS ACTIVITY. ANOTHER SFC TROUGH...FROM THE ATLC CONTINUES TO ENHANCE SOME SHOWER ACTIVITY OVER HISPANIOLA AND THE WINDWARD PASSAGE. A DIFFERENCE IN PRES BETWEEN THE ABOVE MENTIONED ARE OF LOW PRES AND A HIGH N OF AREA IS PRODUCING MODERATE TO FRESH NE AND E WINDS OVER THE NW AND CENTRAL CARIBBEAN...PARTICULARLY WEST OF 75W. THESE WINDS ARE EXPECTED TO PERSIST AT LEAST DURING THE NEXT COUPLE OF DAYS. ATLANTIC OCEAN... BROAD UPPER TROUGH COVERS THE W ATLC WITH THE BASE OF THE TROUGH JUST N OF HISPANIOLA. THE ASSOCIATED COLD FRONT CLIPS THE FORECAST REGION NEAR 31N65W...THEN CONTINUES AS A POST-FRONTAL SURFACE TROUGH TO THE NW BAHAMAS. BROKEN LOW/MID CLOUDS WITH ISOLATED SHOWERS ARE RELATED TO THE TROUGH. A JET STREAM BRANCH WITH CORE WINDS OF 70-90 KT EXTENDS ALONG THE EASTERN EDGE OF OF THE UPPER TROUGH FROM NEAR 22N72W TO BEYOND 32N54W. A STATIONARY FRONT ENTERS THE AREA NEAR 31N48W TO 25N58W CONTINUING AS A SURFACE TROUGH ALONG 21N70W THEN ACROSS HISPANIOLA. AN AREA OF MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS AND ISOLATED THUNDERSTORMS ARE WITHIN 150 NM OF THE FRONT AND WITHIN 80 NM OF SURFACE TROUGH TO ACROSS HISPANIOLA. AN UPPER HIGH IS OVER THE LESSER ANTILLES NEAR 16N60W EXTENDING AN UPPER RIDGE NE ACROSS THE E-CENTRAL ATLC. AN UPPER-LEVEL LOW IS NEAR 13N44W WHILE A NARROW UPPER TROUGH IS OVER THE FAR E ATLC N OF 20N E OF 25W TO THE COAST OF W AFRICA. ANOTHER UPPER RIDGE DOMINATES THE REMAINDER OF THE TROPICAL ATLC S OF 18N E OF 40W. UPPER DIFFLUENCE ASSOCIATED WITH THIS FEATURE IS ENHANCING CONVECTION ALONG THE ITCZ AXIS. $$ GR