000 AXNT20 KNHC 202347 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON OCT 20 2008 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND 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. ...TROPICAL WAVES... A TROPICAL WAVE EMERGED OFF THE WEST COAST OF AFRICA THIS MORNING. ITS AXIS IS CURRENTLY ALONG 20W SOUTH OF 13N MOVING WEST AT 10-15 KT. LATEST VIS IMAGERY FOR THE DAY REVEALS A BROAD CYCLONIC CIRCULATION AND A DISTINCT INVERTED-V CLOUD SIGNATURE AROUND THE WAVE AXIS. THIS FEATURE SHOWS UP VERY WELL ON THE SSMI-TPW PRODUCT WHERE A BULGE OF MOISTURE IS SEEN. SCATTERED MODERATE CONVECTION IS WITHIN 200 NM BEHIND THE WAVE AXIS FROM 11N-14N AND NEAR 8N24W. A TROPICAL WAVE IS ALONG 45W S OF 18N MOVING W NEAR 10 KT. THE TPW PRODUCT FROM CIMSS INDICATES A NORTH-SOUTH MOISTURE MAXIMUM ALONG THE WAVE AXIS. CONVECTION ASSOCIATED WITH THIS WAVE IS RAPIDLY BEING DRAWN NORTHWARD BY AN UPPER-LEVEL LOW LOCATED WEST OF THE WAVE AXIS NEAR 21N51W. A LOW AMPLITUDE TROPICAL WAVE IN THE CENTRAL CARIBBEAN ALONG 71W SOUTH OF 15N MOVING WEST 10-15 KT. THE WAVE IS GENERATING SCATTERED MODERATE CONVECTION OVER WESTERN VENEZUELA INCLUDING THE LAKE MARACAIBO AREA. 850 MB RELATIVE VORTICITY AND THE TPW PRODUCTS FROM CIMSS SUPPORT THE LOCATION OF THE WAVE LINE. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 7N12W 8N22W 4N33W 9N46W TO 8N61W. IN ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL WAVES... SCATTERED MODERATE CONVECTION IS WITHIN 70-90 NM S OF THE AXIS AND WITHIN 45 NM N OF AXIS BETWEEN 24W-30W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 10-14N BETWEEN 48W-58W. A DIFFLUENT PATTERN ALOFT IS HELPING TO INDUCE THIS AREA OF CONVECTION. ...DISCUSSION... GULF OF MEXICO... AN UPPER-LEVEL TROUGH EXTENDING OVER THE SE PORTION OF THE GULF AND THE EASTERN BAY OF CAMPECHE IS PRODUCING MODERATE TO STRONG SUBSIDENCE ACROSS THE ENTIRE GULF REGION. THIS TROUGH IS FORECAST TO DISSIPATE IN ABOUT 24-36 HOURS. AS A RESULT...A ZONAL FLOW WILL DOMINATE THE GULF BY MIDWEEK. AT THE SURFACE... HIGH PRES CENTERED OVER THE SE CONUS EXTENDS A RIDGE ACROSS THE AREA WITH A MOSTLY DRY AND STABLE ATMOSPHERE. E TO NE WINDS OF 10-15 KT ARE FOUND ACROSS MUCH OF THE REGION. WINDS INCREASE TO 20 KT OVER THE SE PORTION OF THE GULF DUE TO THE PRESENCE OF A FRONTAL BOUNDARY OVER THE FAR NW CARIBBEAN AND A SFC LOW OVER THE GULF OF HONDURAS. PATCHY CLOUDS WITH ISOLATED SHOWERS ARE OBSERVED ON SATELLITE IMAGERY PARTICULARLY SOUTH OF 24N BETWEEN 85W-90W. EXPECT THE RIDGE ACROSS THE GULF TO WEAKEN IN ADVANCE OF A WEAK FRONT FORECAST TO MOVE OUT OF THE TEXAS COAST LATE WED. CARIBBEAN SEA... AS OF 2100 UTC...A 1010 MB SURFACE LOW PERSISTS OVER THE GULF OF HONDURAS NEAR 16N87W. THIS SYSTEM IS PRODUCING DISORGANIZED SHOWERS AND THUNDERSTORMS OVER A LARGE PORTION OF THE NW CARIBBEAN SEA...BUT MAINLY FROM 15N-20N BETWEEN 78W-82W. A CLUSTER OF MODERATE CONVECTION IS WITHIN 75 NM JUST NORTH OF THE LOW CENTER. SURFACE PRESSURES ARE RISING IN THIS AREA AND DEVELOPMENT...IF ANY...WILL BE SLOW TO OCCUR. LOCALLY HEAVY RAINS ARE POSSIBLE OVER PORTIONS OF HONDURAS...GUATEMALA... BELIZE...AND THE YUCATAN PENINSULA DURING THE 24-48 HOURS. AN UPPER-LEVEL HIGH LOCATED SOUTH OF HISPANIOLA DOMINATES MOST OF THE CARIBBEAN SEA. UPPER DIFFLUENCE BETWEEN THIS HIGH AND AN UPPER-LEVEL TROUGH OVER THE GULF OF MEXICO IS ENHANCING CONVECTION ASSOCIATED WITH THE AFOREMENTIONED SFC LOW. ACCORDING TO THE GFS MODEL...THIS LOW WILL REMAIN STATIONARY IN THE GULF OF HONDURAS NEAR THE BELIZE COAST DURING THE NEXT COUPLE OF DAYS...THEN WILL MOVE ACROSS THE YUCATAN PENINSULA INTO THE SOUTH-CENTRAL GULF OF MEXICO BY THU. PRES GRADIENT BETWEEN THIS SFC LOW AND HIGH PRES OVER THE GULF OF MEXICO IS PRODUCING MODERATE TO STRONG ELY WINDS ACROSS THE FAR NW CARIBBEAN JUST SOUTH OF CUBA AND ALSO SOUTH OF A STATIONARY FRONT THAT EXTENDS FROM CENTRAL CUBA TO THE NE PORTION OF THE YUCATAN PENINSULA. AN EARLIER QSCAT PASS SHOWED UNCONTAMINATED WIND BARS OF 15 TO 20 KT. IN ADDITION...NOAA BUOY 42056 IN THE NW CARIBBEAN IS ALSO REPORTING ELY WINDS OF 20 KT. MODERATE TRADE WINDS ARE BLOWING ACROSS THE EAST AND CENTRAL CARIBBEAN SEA. EXPECT THE FRONTAL BOUNDARY TO DISSIPATE IN ABOUT 12-24 HOURS. ATLANTIC OCEAN... A DEEP LAYERED TROUGH OVER THE W ATLC SUPPORTS A COLD FRONT THAT ENTERS THE AREA NEAR 31N61W THEN CONTINUES SW THROUGH THE CENTRAL BAHAMAS TO NEAR 22N77W. AT THIS POINT...IT BECOMES STATIONARY CROSSING CENTRAL CUBA AND THE FAR NW CARIBBEAN INTO THE NE PORTION OF THE YUCATAN PENINSULA. A BAND OF MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS IS WITHIN 120 NM AHEAD OF FRONT. TO THE EAST...A 1026 MB HIGH IS SITUATED NEAR 32N36W AND EXTENDS A RIDGE OVER THE REMAINDER OF THE FORECAST AREA. A LARGE UPPER-LEVEL LOW NEAR 21N51W AND AN UPPER-LEVEL HIGH NEAR 19N38W CONTINUE TO FUNNEL DEEP-LAYER TROPICAL MOISTURE NORTHWARD INTO THE CENTRAL ATLC. UPPER-LEVEL DIFFLUENCE BETWEEN THIS LOW AND THE UPPER-LEVEL HIGH LOCATED OVER THE CARIBBEAN SEA IS ENHANCING CONVECTION ALONG THE ITCZ EAST OF THE WINDWARD ISLANDS TO 48W. ANOTHER UPPER-LEVEL TROUGH EXTENDS BETWEEN THE CANARY/CAPE VERDE ISLANDS AND THE WEST COAST OF AFRICA. $$ GR