000 AXNT20 KNHC 132358 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT AUG 13 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 2345 UTC. ...SPECIAL FEATURES... TROPICAL STORM FRANKLIN IS CENTERED NEAR 39.7N 55.5W AT 13/2100 UTC MOVING ENE AT 19 KT. ESTIMATED CENTRAL PRESSURE IS 1004 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUST TO 45 KT. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE FROM 38N-43N BETWEEN 49W-53W. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. A 1013 MB LOW IS CENTERED NEAR 19N54W MOVING WNW AT 15-20 KT. A SURFACE TROUGH IS ANALYZED FROM 22N56W TO THE LOW CENTER. SCATTERED HEAVY SHOWERS AND THUNDERSTORMS ARE FROM 18N-24N BETWEEN 51W-57W. WHILE UPPER-LEVEL WINDS ARE CURRENTLY NOT FAVORABLE FOR DEVELOPMENT...ENVIRONMENTAL CONDITIONS COULD BECOME MORE CONDUCIVE FOR DEVELOPMENT DURING THE NEXT COUPLE OF DAYS. THIS SYSTEM HAS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. A 1012 MB LOW IS NEAR 27N61W...ABOUT 400 NM SE OF BERMUDA. SCATTERED HEAVY SHOWERS AND THUNDERSTORMS ARE WITHIN 50 NM AROUND THE LOW CENTER. THE CLOUD STRUCTURE IS BECOMING BETTER ORGANIZED...AND IF CURRENT TRENDS CONTINUE...ADVISORIES COULD BE INITIATED LATER TONIGHT. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS THE SYSTEM MOVES WNW AT 10-12 KT. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 16N37W TO 10N36W MOVING W AT 10-15 KT. THE WAVE LIES E OF AN AREA OF ENHANCED MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY. WHILE THE WAVE IS CURRENTLY INACTIVE AND HAS NO ASSOCIATED DEEP CONVECTION...MODEL GUIDANCE SHOWS ENHANCED CONVECTION AND SOME DEVELOPMENT OF THE WAVE IN A FEW DAYS. TROPICAL WAVE IS OVER THE YUCATAN PENINSULA ANALYZED FROM 21N87W TO 16N90W MOVING W AT 10-12 KT. MOST OF THE CONVECTION IS INLAND OVER THE YUCATAN PENINSULA...REACHING TO 40 NM OFF THE COASTAL WATERS OF THE PENINSULA. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST OF MAURITANIA NEAR 17N16W ALONG 13N23W TO 10N34W. THE ITCZ IS ANALYZED FROM 10N50W TO THE COAST OF SOUTH AMERICA NEAR 8N60W. ISOLATED SHOWERS ARE WITHIN 20 NM ON EITHER SIDE OF THE ITCZ. SIMILAR ACTIVITY IS WITHIN 100 NM EITHER SIDE OF THE MONSOON TROUGH. SCATTERED SHOWERS ARE OVER THE COASTAL WATERS OF GUINEA...SIERRA LEONE...AND LIBERIA FROM 3N-9N E OF 20W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER RIDGE OF HIGH PRESSURE IS SETTLING ACROSS THE CONUS. THIS FEATURE IS PROVIDING A DRY NE FLOW ALOFT ACROSS THE DISCUSSION AREA. AT LOWER LEVELS...RIDGING IS ACROSS THE AREA CENTERED AROUND A 1015 MB HIGH NEAR 27N90W. WINDS ARE LIGHT AND VARIABLE NEAR THE HIGH CENTER WHILE ANTICYCLONIC 8-10 KT WINDS ARE ELSEWHERE ACROSS THE BASIN. A TROPICAL WAVE IS INLAND OVER THE YUCATAN PENINSULA GENERATING SHOWERS AND THUNDERSTORMS WITHIN 40 NM OVER THE COASTAL WATERS OF YUCATAN. SIMILAR ACTIVITY IS OVER THE COASTAL WATERS OF CUBA W OF 80W...ASSOCIATED TO A WEAK UPPER LEVEL TROUGH OVER THE FAR NW CARIBBEAN EXTENDING INTO THE SE GULF. EXPECT WEAK SURFACE RIDGING TO REMAIN ACROSS THE BASIN OVER THE NEXT 24 HOURS. THE TROPICAL WAVE WILL CONTINUES TO MOVE INTO THE BAY OF CAMPECHE OVER THE NEXT DAY WHICH MAY INCREASE THE CHANCE OF SHOWER ACTIVITY ACROSS THE SRN GULF. CARIBBEAN SEA... A LARGE CLUSTER SHOWERS AND THUNDERSTORMS IS IN THE SW CARIBBEAN S OF 16N W OF 76W ASSOCIATED WITH THE MONSOON TROUGH THAT EXTENDS ACROSS COSTA RICA TO NORTHERN COLOMBIA. THE ACTIVITY IS FURTHER ENHANCED BY AN ELONGATED UPPER LEVEL CYCLONIC CIRCULATION COVERING THE SAME REGION. A WEAK UPPER LEVEL TROUGH OVER THE FAR NW CARIBBEAN IS ALSO GENERATING SIMILAR CONVECTION WITHIN 40 NM OVER THE COASTAL WATERS OF THE YUCATAN PENINSULA AND CUBA W OF 80W. THE REMAINDER OF THE BASIN IS INFLUENCED BY DRY AIR ALOFT ADVECTING FROM THE W TROPICAL ATLC AND SUPPORTING MOSTLY FAIR WEATHER ACROSS THE CENTRAL AND ERN CARIBBEAN WITH 5-15 KT ELY TRADE WINDS. DOPPLER RADAR IMAGERY FROM THE NWS PUERTO RICO INDICATED SCATTERED SHOWERS ACROSS THE WATERS NEAR PUERTO RICO AND THE VIRGIN ISLANDS N OF 15N BETWEEN 64W-68W... ASSOCIATED TO THE SURFACE TROUGH IN THE ATLC N OF PUERTO RICO. EXPECT CONVECTION TO REMAIN OVER THE SW CARIBBEAN ASSOCIATED WITH THE MONSOON TROUGH...AND ACROSS THE WATERS NEAR HISPANIOLA ASSOCIATED WITH THE SURFACE TROUGH N OF PUERTO RICO. ATLANTIC OCEAN... A NEARLY STATIONARY FRONTAL BOUNDARY SKIRTS ACROSS THE NW PORTION OF THE DISCUSSION AREA ALONG 32N BETWEEN 65W AND THE COAST OF SOUTH CAROLINA SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS N OF 29N W OF 74W. SIMILAR ACTIVITY IS WITHIN 30 NM ALONG AN IMAGINARY LINE FROM 25N76W TO 29N68W. NEAR THIS AREA OF CONVECTION...A WEAK 1018 MB HIGH IS CENTERED AROUND 27N67W...PROVIDING FAIR WEATHER ACROSS MUCH OF THE BAHAMAS. THREE AREA OF SCATTERED HEAVY SHOWERS AND THUNDERSTORMS ARE TO THE E OF THIS FEATURE BETWEEN 52W-70W...ASSOCIATED WITH TWO LOW PRESSURE SYSTEMS AND A SURFACE TROUGH N OF PUERTO RICO. THE SURFACE TROUGH IS ANALYZED FROM 24N32W TO 18N64W. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS ON THE TWO LOWS. A BROAD SURFACE RIDGE DOMINATES THE REMAINDER OF THE ATLC...ANCHORED BY A 1024 MB HIGH NEAR 32N42W. LAST VISIBLE SATELLITE PICTURES OF THE DAY INDICATED A BROAD AREA OF AFRICAN DUST EXTENDING E OF THE TWO SURFACE LOW PRESSURE SYSTEMS TO THE AFRICAN COAST. 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