000 AXNT20 KNHC 181137 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST SAT NOV 18 2006 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN 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...WEATHER OBSERVATIONS...RADAR... AND METEOROLOGICAL ANALYSIS. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1115 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 54W S OF 16N MOVING W NEAR 10 KT. THE WAVE IS INTERACTING WITH AN UPPER TROUGH THAT DIGS INTO THE DEEP TROPICS ALONG 58W. SWLY WINDS AHEAD OF THE TROUGH ARE SHEARING THE SHOWER ACTIVITY WELL TO THE E/NE OF THE WAVE. A 1011 MB SURFACE LOW HAS DEVELOPED VERY CLOSE TO THE NORTHERN END OF THE WAVE. LATEST NIGHT CHANNEL VIS IMAGERY SHOWS A WELL DEFINED SWIRL OF LOW LEVEL CLOUDS NEAR 18N51W. WIDELY SCATTERED SHOWERS ARE ASSOCIATED WITH THE WAVE...WHILE AN AREA OF SCATTERED MODERATE CONVECTION IS JUST EAST OF THE LOW PRESSURE FROM 16N-20N BETWEEN 47W-51W. THIS LOW PRESSURE WILL MOVE MAINLY NORTH DURING THE NEXT 12-24 HOURS. A WEAK TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 72W S OF 18N MOVING W 10 TO 15 KT. THIS WAVE IS GENERATING A COUPLE OF CLUSTERS OF MODERATE CONVECTION OVER WESTERN VENEZUELA. ONE OF THEM IS OVER LAKE MARACAIBO. ISOLATED SHOWERS ARE ALSO SEEN OVER HISPANIOLA AND THE COASTAL WATERS. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 10N14W 5N30W 6N40W 9N52W. THE ITCZ IS PRETTY ACTIVE EARLY THIS MORNING WITH SCATTERED MODERATE TO ISOLATED STRONG CONVECTION MAINLY NORTH OF THE AXIS...AND FROM 4N-9N BETWEEN 20W-40W. SIMILAR CONVECTION IS ALSO FOUND WITHIN 100 NM ON EITHER SIDE OF THE AXIS BETWEEN 48W-48W. ...DISCUSSION... THE GULF OF MEXICO... A BROAD DEEP LAYERED TROUGH EXTENDS ALONG THE EASTERN U.S./GULF OF MEXICO NORTH OF 24N. THE BASE OF THE TROUGH REACHES SOUTH FLORIDA. ABUNDANT UPPER LEVEL MOISTURE IS BEEN ADVECTED FROM T.S. SERGIO AND THE ITCZ IN THE EPAC ACROSS SOUTHERN MEXICO AND THE YUCATAN PENINSULA INTO CUBA AND THE BAHAMAS. THIS PLUME OF MOISTURE IS SLOWLY SWEEPING SE CLEARING THE GULF. DRY AND STABLE AIR ALOFT...RESULTING IN MODERATE TO STRONG SUBSIDENCE DOMINATES MOST OF THE AREA WHERE COOL/DRY CONDITIONS WITH LIGHT LOW-LEVEL WINDS PREVAIL. A 1019 MB SURFACE HIGH CENTERED OVER LOUISIANA COVERS THE ENTIRE GULF. A REINFORCING FRONT WILL MOVE ACROSS THE GULF ON SUNDAY FOLLOWED BY STRONG NLY WINDS AND BUILDING SEAS. THESE WEATHER CONDITIONS ARE EXPECTED TO PERSIST THROUGH TUESDAY. ON THIS DAY...THE GFS MODEL DEVELOPS A LOW PRESSURE EAST OF FLORIDA. THE PRESSURE GRADIENT WILL TIGHTEN BETWEEN THIS LOW AND THE HIGH PRESSURE OVER THE GULF...RESULTING IN STRONG NLY WINDS OVER THE EASTERN GULF OF MEXICO...THE FLORIDA PENINSULA AND THE NW CARIBBEAN. THE CARIBBEAN SEA... A BROAD UPPER RIDGE DOMINATES MOST OF THE CARIBBEAN WATERS AND CENTRAL AMERICA FROM AN UPPER HIGH NOW LOCATED NEAR 13N79W. A STATIONARY FRONT REMAINS OVER THE NW CARIBBEAN AND CENTRAL CUBA/BAHAMAS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS. AN AREA OF MODERATE TO ISOLATED STRONG CONVECTION HAS DEVELOPED AHEAD OF THE FRONT AND VERY CLOSE TO THE CARIBBEAN PLAINS OF COSTA RICA AND NICARAGUA. THIS CONVECTIVE ACTIVITY COVERS FROM 9N-17N BETWEEN 80W-84W. A DIFFLUENT PATTERN ALOFT IS ENHANCING THIS SHOWER/TSTM ACTIVITY. THE REMAINDER OF THE BASIN IS QUIET WITH STABLE AIR ALOFT...PARTICULARLY THE ERN CARIBBEAN. ONLY SCATTERED SHOWERS ARE SEEN EMBEDDED IN THE TRADE WINDS. THE STATIONARY FRONT WILL GRADUALLY WEAKEN TO A FRONTAL TROUGH. A REINFORCING COLD FRONT MOVING THROUGH THE GULF OF MEXICO ON SUNDAY WILL CAUSE WINDS TO INCREASE OVER THE WESTERN CARIBBEAN MON THROUGH WED. THE ATLANTIC OCEAN... THE BASE OF A BROAD DEEP LAYERED TROUGH THAT LIES ACROSS THE EASTERN U.S. EXTENDS ACROSS THE ERN GULF...THE STATE OF FLORIDA AND THE FAR W ATLC. THE ASSOCIATED FRONTAL SYSTEM ENTERS THE AREA NEAR 32N71W THEN CONTINUES SW ACROSS THE CENTRAL BAHAMAS AND CUBA WHERE IT BECOMES STATIONARY. INSTABILITY ASSOCIATED WITH THE FRONTAL BOUNDARY ALONG WITH A DIFFLUENT PATTERN ALOFT ARE GENERATING PATCHES OF SCATTERED MODERATE CONVECTION WITHIN 80-100 NM AHEAD OF THE FRONT FROM 23N-29N. A NARROW UPPER RIDGE EXTENDS FROM THE CARIBBEAN ACROSS CUBA AND THE BAHAMAS INTO THE REMAINDER OF THE W ATLC TO 32N66W AND BEYOND. A LARGE CUT OFF UPPER LOW IS EAST OF THE RIDGE NEAR 28N56W. AN UPPER TROUGH EXTENDS SW FROM THIS LOW INTO THE DEEP TROPICS NEAR 11N-58W. VERY DRY AIR LIES TO THE W AND S OF THE UPPER LOW EXTENDING INTO THE ERN CARIBBEAN. A LARGE AREA OF SCATTERED SHOWERS AND ISOLATED TSTMS EXISTS AHEAD OF THIS TROUGH FROM 20N-32N BETWEEN 45W-56W. A 1012 MB SURFACE LOW REMAINS NEAR 29N60W. ANOTHER UPPER RIDGE EXTENDS NORTH FROM THE TROPICS ALONG 42W. THE FLOW THEN BECOMES NEARLY ZONAL E OF 30W. A 1027 MB SURFACE HIGH LOCATED WELL NORTH OF THE AREA EXTENDS A RIDGE OVER THE EASTERN ATLC GIVING THE REGION MOSTLY FAIR WEATHER. AN UPPER LOW WITH SOME SHOWERS IS APPROACHING THE MADEIRA/CANARY ISLANDS. $$ GR