000 AXNT20 KNHC 232344 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SUN OCT 23 2011 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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2300 UTC. ...SPECIAL FEATURES... THE AREA OF LOW PRESSURE THAT HAS BEEN IMPACTING THE WRN CARIBBEAN IS NOW TROPICAL DEPRESSION EIGHTEEN. T.D. EIGHTEEN IS CENTERED NEAR 16.1N 82.0W. AT 24/0000 UTC..OR ABOUT 90 NM NE OF CABO GRACIAS A DIO ON THE HONDURAS/NICARAGUA BORDER...MOVING NNW AT 10 KT. MINIMUM CENTRAL PRESSURE IS 1004 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS MAINLY N OF THE CENTER FROM 16N-21N BETWEEN 78W-84W...WITH SCATTERED MODERATE CONVECTION FROM 14N-19N BETWEEN 84W-86W. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT3/WTNT33 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 13N17W ALONG 12N28W 9N38W. SCATTERED MODERATE/STRONG CONVECTION IS WITHIN 260 NM N OF THE AXIS...AS WELL AS FROM 5N-12N BETWEEN 38W-46W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL TROUGH IS SINKING INTO THE GULF OF MEXICO THIS EVENING FROM ALABAMA TO THE SRN TIP OF TEXAS. HOWEVER...DUE TO AN EXTREMELY DRY AIRMASS SITTING ACROSS THE BASIN...FAIR WEATHER PREVAILS AROUND A WEAK SURFACE RIDGE EXTENDING NE TO SW. PATCHES OF STRATOCUMULUS CLOUDS ARE EVIDENT IN SATELLITE IMAGERY ACROSS THE SRN HALF OF BASIN WITH ONLY A FEW ISOLATED SHOWERS IN THE FAR SRN BAY OF CAMPECHE. SURFACE RIDGING AND MOSTLY FAIR CONDITIONS ARE EXPECTED TO REMAIN ACROSS THE BASIN FOR THE NEXT SEVERAL DAYS. THE CHANCE FOR SHOWER ACTIVITY MAY INCREASE OVER THE SE GULF AS MOISTURE FROM T.D. EIGHTEEN IN THE WRN CARIBBEAN DRIFTS NWD. CARIBBEAN SEA... T.D. EIGHTEEN IS THE MAIN INTEREST IN THE CARIBBEAN TONIGHT PROVIDING MOIST CONDITIONS BETWEEN JAMAICA AND THE YUCATAN PENINSULA. HEAVY RAINFALL IS POSSIBLE OVER NICARAGUA AND HONDURAS AS THE SYSTEM MOVES NNW WITH THE POTENTIAL FOR FLOODING AND MUDSLIDES. A WEAKENING STATIONARY FRONT THAT WAS N OF WHAT IS NOW T.D. EIGHTEEN HAS DISSIPATED AS OF 2100 UTC. ALOFT...AN UPPER LEVEL RIDGE IS CENTERED JUST S OF ERN CUBA NEAR 19N76W. THE REMAINDER OF THE BASIN IS COVERED BY MODERATE DRY AIR ALOFT...WHICH IS PROVIDING MOSTLY FAIR CONDITIONS E OF 75W. A FEW ISOLATED SHOWERS ARE BEGINNING TO IMPACT THE LESSER ANTILLES ASSOCIATED WITH A 1008 MB LOW E OF THE ISLANDS. EXPECT MOIST AND WINDY CONDITIONS TO REMAIN OVER THE WRN CARIBBEAN IN ASSOCIATED WITH T.D. EIGHTEEN. THE LOW E OF THE WINDWARD ISLANDS IS EXPECTED TO MOVE WWD TOWARDS THE BASIN BRINGING A HIGHER CHANCE OF SHOWERS TO THE ERN CARIBBEAN. ATLANTIC OCEAN... A BROAD LONGWAVE UPPER TROUGH IS MOVING ACROSS THE ERN CONUS AND FAR WRN ATLC SUPPORTING A DISSIPATING STATIONARY FRONT ENTERING THE DISCUSSION AREA NEAR 31N70W CONTINUING ALONG 27N77W 23N78W. ISOLATED SHOWERS ARE WITHIN 175 NM W OF THE BOUNDARY. A WEAK SURFACE TROUGH IS E OF THE FRONT ALONG 28N69W 23N74W CAUSING NO ACTIVE WEATHER. A SHORTWAVE UPPER TROUGH EXTENDS OFF THE MAIN TROUGH ALONG 61W SUPPORTING CLUSTERS OF SHOWERS/THUNDERSTORMS N OF 26N BETWEEN 57W-61W. FARTHER S...A 1008 MB SURFACE LOW IS E OF THE WINDWARD ISLANDS NEAR 12N56W. THE CIRCULATION IS BROAD AND WEAK. ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE FROM 9N-16N BETWEEN 53W-61W. THE REMAINDER OF THE BASIN IS DOMINATED BY SURFACE RIDGING AROUND A 1024 MB HIGH NEAR 34N44W PROVIDING MOSTLY FAIR WEATHER ACROSS THIS PORTION OF THE BASIN. THE SURFACE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE CENTERED NEAR 28N43W. A NARROW UPPER LEVEL TROUGH EXTENDS JUST ALONG THE NW AFRICAN COAST AND WRAPS AROUND THE SE SIDE OF THE UPPER RIDGE. THIS IS PROVIDING THE DIFFLUENCE ALOFT TO ENHANCE SOME OF THE ACTIVITY N OF THE MONSOON TROUGH. THE UPPER TROUGH ALSO SUPPORTS A SURFACE TROUGH ALONG 16N39W TO 12N47W N OF THE CONVECTIVE ACTIVITY N OF THE MONSOON TROUGH. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON