000 AXNT20 KNHC 121801 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST MON NOV 12 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 67W/68W S OF 16N MOVING W NEAR 20 KT. VIS SATELLITE IMAGERY AND THE SAHARAN AIR LAYER PRODUCT FROM CIMMS ARE STILL SHOWING A LARGE SURGE OF AFRICAN DUST JUST BEHIND THE WAVE AXIS. MOST OF THE LESSER ANTILLES HAVE REPORTED HAZE SINCE YESTERDAY. THE WAVE IS GENERATING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF 16N BETWEEN 66W-72W...INCLUDING THE ABC ISLANDS. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 8N13W 6N25W 7N40W 7N50W 5N57W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION COVERS THE AREA FROM 4N-10N E OF 21W. SIMILAR CONVECTION IS WITHIN 200 NM N OF AXIS BETWEEN 25W-30W...AND WITHIN 90/120 NM EITHER SIDE OF AXIS FROM 36W-44W. DISCUSSION... GULF OF MEXICO... THE GULF CONTINUES UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED ON A HIGH CENTERED OVER THE CAROLINAS. THIS FEATURE IS PRODUCING MOSTLY FAIR WEATHER AND LIGHT TO MODERATE WINDS OVER THE REGION. A LINE OF MAINLY LOW/MID CLOUDS WITH EMBEDDED SHOWERS HAS FORMED OVER THE WESTERN GULF ALONG 94W/95W ASSOCIATED WITH THE SE RETURN FLOW ON THE WESTERN SIDE OF THE RIDGE. SFC OBSERVATIONS FROM 1500 UTC AND AN EARLIER ASCAT PASS INDICATED E TO SE WINDS UP TO 20 KT OVER THE SW PORTION OF THE GULF. ALOFT...BROAD UPPER RIDGE EXTENDS FROM THE W CARIBBEAN ACROSS THE YUCATAN PENINSULA/CHANNEL INTO THE GULF WHERE UPPER LEVEL WINDS ARE NEARLY ZONAL. MID/UPPER DRY AIR...RESULTING IN MODERATE TO STRONG SUBSIDENCE ALSO COVERS THE AREA LIMITING THE DEVELOPMENT OF DEEP CONVECTION. NO MAJOR CHANGES IN THE WEATHER PATTERN ARE EXPECTED AS HIGH PRESSURE OVER THE CAROLINAS SHIFTS SOUTH OVER THE NORTHERN CENTRAL GULF BY MID WEEK. LOOKING AHEAD...THE NEXT COLD FRONT IS FORECAST TO MOVE ACROSS THE GULF ON THURSDAY WITH AN INCREASE IN WINDS AND SEAS. CARIBBEAN SEA... ATTENTION REMAINS FOCUSED ON AN ELONGATED AREA OF CLOUDINESS... SHOWERS...AND THUNDERSTORMS COVERING PARTS OF THE WEST AND SW CARIBBEAN. THIS ACTIVITY IS ASSOCIATED WITH A 1008 MB LOW PRESSURE LOCATED NEAR THE EAST COAST OF SOUTHERN NICARAGUA. THIS SYSTEM IS POORLY ORGANIZED AND TROPICAL CYCLONE DEVELOPMENT IS NOT EXPECTED. A SWIRL OF LOW LEVEL CLOUDS DEFINES THE LOW PRES WHILE MOST OF THE CONVECTIVE ACTIVITY IS WITHIN 120 NM NORTH OF CENTER. THE MOST SIGNIFICANT IMPACT WITH THIS SYSTEM REMAINS THE POTENTIAL FOR LOCALLY HEAVY RAIN OVER PORTIONS OF COSTA RICA...NICARAGUA AND HONDURAS DURING THE NEXT COUPLE OF DAYS. VIS SATELLITE IMAGERY INDICATES THAT PART OF THE SHOWER/TSTM ACTIVITY ASSOCIATED WITH THIS SYSTEM IS ALREADY AFFECTING THESE COUNTRIES. A SFC TROUGH EXTENDS FROM THIS LOW TO NEAR THE CAYMAN ISLANDS. CLUSTERS OF MODERATE TO STRONG CONVECTION ARE MAINLY ON THE EAST SIDE OF THE TROUGH FROM 11N-18N WEST OF 77W...WITH LIGHTNING DATA SUPPORTING SCATTERED TSTMS MAINLY NEAR 13N78W AND 16N80W. CONVECTION HAS ALSO FLARED UP OVER JAMAICA AND COASTAL WATERS. BROAD UPPER RIDGE EXTENDING ACROSS THE BASIN FROM AN UPPER HIGH LOCATED JUST EAST OF THE LESSER ANTILLES IS PROVIDING ENOUGH UPPER LEVEL DIFFLUENCE TO GENERATE ALL THIS CONVECTION. A NARROW LINE OF SHOWERS WITH EMBEDDED TSTMS EXTENDS FROM PUERTO RICO NEWD ACROSS THE W/CENTRAL ATLC. THIS LINE MARKS THE LEADING EDGE OF THE AFRICAN DUST THAT HAS FILTERED IN THE EASTERN CARIBBEAN...AND ALSO SEPARATES LIGHTER ELY WINDS FROM STRONGER NE WINDS IN THE RANGE OF 20-25 KT. THE SAN JUAN DOPPLER RADAR SHOWS SCATTERED TO NUMEROUS SHOWERS AND ISOLATED TSTMS MAINLY OVER THE SW AND WEST INTERIOR OF PUERTO RICO...CAPABLE OF PRODUCING LOCALLY HEAVY RAIN. ANOTHER SFC TROUGH...REMNANTS OF AN OLD FRONTAL BOUNDARY RESIDES OVER NORTHERN HISPANIOLA GENERATING SCATTERED TO NUMEROUS SHOWERS AND ISOLATED TSTMS. THE BASE OF AN UPPER-LEVEL TROUGH OVER THE W-CENTRAL ATLC IS ENHANCING THIS ACTIVITY. ATLANTIC OCEAN... BROAD UPPER TROUGH COVERS THE W-CENTRAL ATLC WITH THE BASE OF THE TROUGH JUST N OF HISPANIOLA. THE ASSOCIATED COLD FRONT CLIPS THE FORECAST REGION NEAR 31N54W...THEN CONTINUES AS A WEAKENING SURFACE TROUGH TO THE CENTRAL BAHAMAS INTO THE STRAITS OF FLORIDA. PATCHES OF LOW/MID CLOUDS WITH ISOLATED SHOWERS ARE RELATED TO THE TROUGH MAINLY BETWEEN 60W-70W. A JET STREAM BRANCH WITH CORE WINDS OF 70-85 KT EXTENDS OVER THE W ATLC N OF 27N. ANOTHER SFC TROUGH ENTERS THE AREA NEAR 30N45W THEN CONTINUES SW TO THE NORTHERN COAST OF HISPANIOLA. A BAND OF MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS AND ISOLATED THUNDERSTORMS IS RELATED TO THIS TROUGH. AN UPPER HIGH IS JUST N OF BARBADOS EXTENDING A RIDGE NE ACROSS THE CENTRAL ATLC TO BEYOND 32N35W. AN UPPER-LEVEL TROUGH IS OVER THE FAR E ATLC EXTENDING SW TO A CUT-OFF LOW NEAR 14N41W...THEN CONTINUING TO N SOUTH-AMERICA JUST OFFSHORE OF FRENCH GUIANA. THE TYPICAL E/W UPPER RIDGE CROSS THE TROPICAL ATLC E OF 40W IS HELPING TO INDUCE SHOWERS AND TSTMS ALONG THE ITCZ. $$ GR