000 AXNT20 KNHC 301754 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT WED APR 30 2008 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. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 6N10W 4N20W 1N30W 1N45W INTO NE BRAZIL. CLUSTERS OF MODERATE TO STRONG CONVECTION ARE OVER PARTS OF SIERRA LEONE AND LIBERIA. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 180 NM N OF AXIS BETWEEN 28W AND 31W...AND WITHIN 130 NM S OF AXIS BETWEEN 30W AND 36W. SIMILAR CONVECTION IS FOUND NEAR 2N50W. ...DISCUSSION... GULF OF MEXICO... SFC HIGH PRES LOCATED OVER THE SE CONUS EXTENDS A RIDGE OVER MOST OF GULF REGION AND THE STATE OF FLORIDA WITH MOSTLY FAIR WEATHER AND LIGHT TO MODERATE E TO SE WINDS. 15 TO 20 KT SLY RETURN FLOW HAS BEGAN TO ESTABLISH OVER THE NW CORNER OF THE GULF. SATELLITE IMAGERY SHOWS SCATTERED COLD AIR STRATOCUMULUS CLOUDS MOVING N UNDER THE INFLUENCE OF THESE WINDS. ALOFT... A RIDGE IS BUILDING OVER THE WESTERN GULF WHILE A BROAD DEEP LAYERED TROUGH IS ALONG THE EASTERN SEABOARD SUPPORTING A COLD FRONT THAT IS ALREADY OVER THE W ATLC AND THE CENTRAL BAHAMAS. UPPER LEVEL MOISTURE/HIGH CLOUDS ARE SEEN OVER THE BAY OF CAMPECHE...THE YUCATAN PENINSULA AND THE SE GULF. STRONG SUBSIDENCE AND DRY AIR COVER THE REMAINDER OF THE AREA BUT MAINLY THE NE QUADRANT OF THE GULF. LOOKING AHEAD...A NEW COLD FRONT IS FORECAST TO ENTER NW GULF WATERS FRI NIGHT. CARIBBEAN SEA... BROAD UPPER RIDGE COVERS THE CARIBBEAN ANCHORED ON AN UPPER HIGH CENTERED OVER CENTRAL VENEZUELA. THIS FEATURE IS DRAWING UPPER LEVEL MOISTURE ACROSS CENTRAL AMERICA AND THE CARIBBEAN SEA WEST OF 70W...AND IS ALSO ENHANCING CONVECTION OVER THE SW CARIBBEAN NEAR THE COLOMBIA/PANAMA BORDER. A DYING FRONTAL BOUNDARY EXTENDS FROM E-CENTRAL CUBA TO BELIZE AND N GUATEMALA GENERATING ONLY ISOLATED SHOWERS. THIS FRONT WILL CONTINUE TO DISSIPATE THIS AFTERNOON AND TONIGHT. A PATCH OF MOISTURE WITH EMBEDDED SHOWERS...PREVIOUSLY ASSOCIATED WITH A WEAK SURFACE TROUGH IS JUST SOUTH OF THE CAYMAN ISLANDS. UPPER-LEVEL SUBSIDENCE AND DRY AIR DOMINATE THE EASTERN CARIBBEAN...INCLUDING PUERTO RICO AND VIRGIN ISLANDS AND THE N TROPICAL ATLC. STREAMERS OR CLOUD LINES ARE FORMING OVER THE NE CARIBBEAN UNDER THE INFLUENCE OF AN ELY WIND FLOW. MODERATE TO STRONG TRADE WINDS ARE BLOWING ACROSS MOST OF THE BASIN WITH THE EXCEPTION NW OF THE FRONT. ATLANTIC OCEAN... DEEP LAYERED TROUGH IS OVER THE EASTERN SEABOARD WITH THE BASE OF THE TROUGH REACHING THE NW BAHAMAS. THE ATTENDANT COLD FRONT ENTERS THE FORECAST AREA NEAR 31N66W THEN CONTINUES SW TO THE CENTRAL BAHAMAS. AT THIS POINT...THE FRONTAL BOUNDARY BECOMES STATIONARY EXTENDING OVER E-CENTRAL CUBA AND THE NW CARIBBEAN. SCATTERED SHOWERS AND PROBABLY ISOLATED TSTMS ARE WITHIN 80 NM AHEAD OF THE FRONT N OF 23N. BROAD UPPER RIDGE THAT COVERS THE CARIBBEAN SEA EXTENDS INTO THE W-CENTRAL ATLC THROUGH HISPANIOLA AND PUERTO RICO TO BEYOND 32N57W. SWLY UPPER LEVEL FLOW ON THE WESTERN PERIPHERY OF THE RIDGE IS ADVECTING UPPER LEVEL MOISTURE ACROSS THE SE GULF OF MEXICO/NW CARIBBEAN TO OVER THE W-CENTRAL ATLC. A WEAK 1018 SFC HIGH IS OVER THE CENTRAL ATLC NEAR 26N61W. THIS SYSTEM WILL MOVE SE DURING THE NEXT 24 HOURS OR SO. A SFC TROUGH...REMNANTS OF AN OLD FRONTAL BOUNDARY LIES AHEAD OF THIS ANTICYCLONE ALONG 31N38W 20N50W TO 19N65W. SATELLITE PHOTOS INDICATE A NARROW BAND OF MAINLY LOW CLOUDS ASSOCIATED WITH THIS TROUGH. ANOTHER SFC TROUGH IS OVER THE E ATLC AND RUNS FROM 31N31W TO 20N22W. DUE TO THE LACK OF SFC OBSERVATIONS...THE POSITION OF THIS TROUGH IS BASED MAINLY ON CONTINUITY AND AN ASCAT PASS FROM AROUND 1100 UTC. NE OF THIS SECOND TROUGH... THERE IS A SFC RIDGE EXTENDING FROM THE AZORES TO THE CANARY ISLANDS. PRES GRADIENT BETWEEN THIS RIDGE AND LOWER PRES OVER W AFRICA IS PRODUCING A SWATH OF 20 TO 30 KT NELY WINDS BETWEEN THE MADEIRA ISLANDS AND THE ATL COAST OF MOROCCO. A DEEP LAYERED TROUGH IS OVER THE CENTRAL ATLC WHILE A BROAD UPPER RIDGE COVERS THE E ATLC WITH THE AXIS ALONG 22/23W. UPPER DIFFLUENCE BETWEEN THESE TWO UPPER FEATURES IS HELPING TO INDUCE ISOLATED TO SCATTERED SHOWERS NEAR THE SFC TROUGH OVER THE E ATLC. $$ GR