000 AXNT20 KNHC 172342 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU MAY 17 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...THE ITCZ... THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...6N10W 6.5N30W 3N521W. SCATTERED MODERATE CONVECTION IS JUST N OF THE AXIS FROM 3N-6N WEST OF 45W. ISOLATED MODERATE CONVECTION IS WITHIN 20-40 NM N OF THE AXIS BETWEEN 15W-42W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE OVER LIBERIA AND SIERRA LEONE...AND OVER FRENCH GUIANA AND SURINAME. ...DISCUSSION... THE GULF OF MEXICO... A BROAD MIDDLE/UPPER LEVEL TROUGH DOMINATES THE EASTERN U.S. AND THE FAR E GULF. THIS TROUGH SUPPORTS A COLD FRONT THAT EXTENDS FROM SE GEORGIA TO NEAR BROWNSVILLE TEXAS. THE FRONT IS WEAKENING WEST OF 90W. HIGH PRES IS BUILDING IN BEHIND THE FRONT GIVING THE AREA MAINLY LIGHT TO MODERATE NLY WINDS. VIS SAT IMAGERY SHOWS SCATTERED LOW CLOUDS ASSOCIATED WITH THE FRONTAL BOUNDARY WHILE A DRIER AIRMASS IS INVADING THE NORTHERN GULF WATERS. THE FRONT WILL CONTINUE TO MOVE SLOWLY SOUTH. AN UPPER RIDGE IS OVER MEXICO AND THE W GULF INCLUDING ALSO THE YUCATAN PENINSULA. DRY AIR/SUBSIDENCE COVERS THE AREA SOUTH OF 22N. A WEAK SURFACE PRESSURE GRADIENT COVERS THE REST OF THE GULF OF MEXICO AWAY FROM THE FRONT. THE CARIBBEAN SEA... AN UPPER LEVEL TROUGH FROM THE GULF OF MEXICO DIGS INTO WESTERN CUBA AND THE NW CARIBBEAN. UPPER LEVEL NORTHWESTERLY-TO-WESTERLY WIND FLOW DOMINATES THE BASIN. AN UPPER RIDGE REMAINS OVER NORTHERN SOUTH AMERICA/CENTRAL AMERICA AND THE EPAC. AS OF 21Z...A 1011 MB SFC LOW IS ANALYZED NEAR 18N83W. A TROUGH EXTENDS FROM THIS LOW TO THE COLOMBIAN COAST. THIS TROUGH COMBINED WITH THE CLOSE PROXIMITY OF THE EPAC ITCZ AND A DIFFLUENT PATTERN ALOFT IS GENERATING BROKEN TO OVERCAST MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS AND TSTMS OVER THE SW CARIBBEAN...PANAMA AND COSTA RICA AS WELL AS OVER THE CARIBBEAN PLAINS OF NICARAGUA. CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION ARE ALSO SEEN OVER N COLOMBIA AND THE LAKE MARACAIBO AREA. ANOTHER SFC TROUGH CROSSES CENTRAL CUBA AND EXTENDS SW FROM A 1011 MB LOW LOCATED NEAR GRAN ABACO IN THE NW BAHAMAS. A SWIRL OF LOW CLOUDS DEFINES THIS FEATURE WITH AN EXTENSIVE AREA OF CLOUDINESS JUST E OF THE SFC LOW. THE TROUGH OVER THE W CARIBBEAN WILL REMAIN STATIONARY AND THE LOW IS FORECAST TO MOVE ALONG THE TROUGH TOWARD CUBA. MODERATE TRADE WINDS ARE BLOWING ACROSS THE CENTRAL AND EASTERN CARIBBEAN. THE ATLANTIC OCEAN... AS PREVIOUSLY MENTIONED...A 1011 MB SFC LOW NEAR THE GRAN ABACO ISLAND IS GENERATING A LARGE AREA OF CLOUDINESS WITH EMBEDDED SHOWERS AND TSTMS. A DIFLUENT PATTERN ALOFT...ASSOCIATED WITH AN UPPER RIDGE OVER THE AREA...IS ENHANCING THIS CONVECTIVE ACTIVITY. A TROUGH EXTENDS FROM NEAR 31N73W TO THE LOW AND CONTINUES INTO CENTRAL CUBA/NORTHWESTERN CARIBBEAN. THE LOW IS EXPECTED TO MOVE NORTH OF 31N IN 24 HOURS AND DEVELOP INTO A GALE NORTH OF THE DISCUSSION AREA. A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM A CYCLONIC CIRCULATION CENTER NEAR 28N49W TO 19N50W. THIS TROUGH SUPPORTS THE ATLANTIC OCEAN STATIONARY TROUGH THAT PASSES THROUGH 31N48W TO 21N54W. A WEAK SFC LOW HAS DEVELOPED ALONG THE TROUGH AXIS NEAR 28N49W. THIS LOW IS FORECAST TO MOVE N WITH LITTLE CHANGE. A SURFACE RIDGE EXTENDS SOUTH INTO THE AREA ALONG 60W. ANOTHER RIDGE IS EAST WITH THE AXIS ALONG 35W. ANOTHER MIDDLE TO UPPER LEVEL TROUGH IS FAR EASTERN ATLANTIC N OF 20N. UPPER SWLY WINDS ARE ADVECTING UPPER LEVEL MOISTURE ACROSS THE TROPICS E OF 40W INTO THE CAPE VERDE ISLANDS AND WEST AFRICA. $$ GR