000 AXNT20 KNHC 131752 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURES... TROPICAL STORM FRANKLIN IS CENTERED NEAR 39.0N 57.9W AT 13/1500 UTC 0R ABOUT 525 NM NE OF BERMUDA MOVING ENE AT 19 KT. ESTIMATED CENTRAL PRESSURE IS 1004 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUST TO 50 KT. MODERATE/STRONG CONVECTION IS FROM 39N-43N BETWEEN 55W-59W. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. A 1013 MB LOW IS CENTERED NEAR 20N53W MOVING WNW AT 15-20 KT. SHOWER ACTIVITY HAS INCREASED OVER THE PAST COUPLE OF HOURS AROUND THE NRN HALF OF THE LOW. SCATTERED MODERATE/STRONG CONVECTION IS FROM 19N-23N BETWEEN 51W-55W. ENVIRONMENTAL CONDITIONS ARE MARGINALLY FAVORABLE FOR DEVELOPMENT OVER THE NEXT COUPLE OF DAYS. A SURFACE TROUGH EXTENDS FROM A 1012 MB LOW NEAR 27N60W...ABOUT 370 NM SE OF BERMUDA...WITH AXIS EXTENDING TO N OF PUERTO RICO ALONG 23N61W 20N65W. SCATTERED MODERATE CONVECTION IS NEAR THE LOW CENTER FROM 25N-28N BETWEEN 56W-60W. SIMILAR ACTIVITY IS W OF THE TROUGH AXIS FROM 18N-23N BETWEEN 63W-69W. UPPER-LEVEL CONDITIONS ARE BECOMING MORE FAVORABLE FOR DEVELOPMENT OVER THE NEXT COUPLE OF DAYS AS THE SYSTEM MOVES WNW AT 10-12 KT. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 17N33W TO 12N34W 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 APPROACHING THE YUCATAN PENINSULA IN THE WRN CARIBBEAN ALONG 85W FROM 12N-21N MOVING W AT 10-12 KT. SOME MODERATE DEEP LAYER MOISTURE ACCOMPANIES THE WAVE AND IS ACROSS THE FAR NW CARIBBEAN. SCATTERED MODERATE CONVECTION IS FROM 19N-23N BETWEEN 82W-85W. ...ITCZ/MONSOON TROUGH... MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 18N16W ALONG 13N27W 10N40W. THE ITCZ CONTINUES FROM 10N40W TO 8N60W. SCATTERED MODERATE CONVECTION IS FROM 6N-9N BETWEEN 14W-19W. ISOLATED MODERATE CONVECTION IS FROM 9N-13N BETWEEN 37W-42W. ...DISCUSSION... GULF OF MEXICO... SURFACE RIDGING IS ACROSS THE GULF OF MEXICO TODAY AROUND A 1015 MB HIGH NEAR 28N87W PROVIDING MOSTLY FAIR CONDITIONS ACROSS THE BASIN. HOWEVER...SOME DEEP LAYER MOISTURE HAS MOVED OVER THE FAR ERN GULF WHICH IS HELPING ENHANCE ISOLATED SHOWERS/THUNDERSTORMS N OF 24N E OF 84W. SIMILAR ACTIVITY IS ALSO ALONG THE LOUISIANA/MISSISSIPPI COASTLINES. ALOFT...NELY FLOW COVERS THE WRN HALF OF THE AREA AROUND AN UPPER LEVEL RIDGE CENTERED OVER WRN TEXAS. A WEAK UPPER LEVEL TROUGH IS OVER THE FAR NW CARIBBEAN EXTENDING INTO THE SE GULF. ANOTHER SHORTWAVE TROUGH DIPS DOWN FROM THE N ACROSS THE NE GULF. EXPECT WEAK SURFACE RIDGING TO REMAIN ACROSS THE BASIN. A TROPICAL WAVE OVER THE NW CARIBBEAN WILL BEGIN TO MOVE ACROSS THE YUCATAN PENINSULA AND INTO THE BAY OF CAMPECHE OVER THE NEXT DAY WHICH MAY INCREASE THE CHANCE OF SHOWER ACTIVITY ACROSS THE SRN GULF. CARIBBEAN SEA... A TROPICAL WAVE OVER THE NW CARIBBEAN IS SUPPORTING A FEW SHOWERS/THUNDERSTORMS S OF WRN CUBA. SEE TROPICAL WAVE SECTION ABOVE. A LARGE CLUSTER OF SHOWERS/THUNDERSTORMS IS IN THE SW CARIBBEAN FROM 12N-15N BETWEEN 75W-83W ASSOCIATED WITH THE MONSOON TROUGH THAT EXTENDS ACROSS COSTA RICA TO 12N80W CONTINUING TO NRN COLOMBIA. ALOFT...AN UPPER LEVEL LOW IS CENTERED E OF NICARAGUA NEAR 14N81W WHICH IS HELPING ENHANCE CONVECTION OVER THE SW CARIBBEAN. THE REMAINDER OF THE BASIN IS INFLUENCED BY DRY AIR ALOFT AROUND A BROAD UPPER RIDGE OVER THE WRN ATLC. THIS PATTERN IS SUPPORTING MOSTLY FAIR WEATHER ACROSS THE CENTRAL AND ERN CARIBBEAN WITH 15-20 KT ELY TRADEWINDS. SCATTERED SHOWERS ARE NOTED ACROSS PUERTO RICO AND THE VIRGIN ISLANDS N OF 18N BETWEEN 64W-68W ASSOCIATED WITH A SURFACE TROUGH IN THE ATLC THAT EXTENDS TO N OF PUERTO RICO NEAR 20N65W. EXPECT EXPECT SHOWER/THUNDERSTORM ACTIVITY TO REMAIN OVER THE NW CARIBBEAN AS THE TROPICAL WAVE MOVES WWD. ACTIVITY WILL ALSO REMAIN OVER THE SW CARIBBEAN ASSOCIATED WITH THE MONSOON TROUGH...AND ACROSS THE N CENTRAL ISLANDS DUE TO MOISTURE ASSOCIATED WITH THE SURFACE TROUGH N OF PUERTO RICO. ATLANTIC OCEAN... A STATIONARY FRONTAL BOUNDARY SKIRTS THE NW PORTION OF THE DISCUSSION AREA ALONG 31N BETWEEN 71W-78W SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS N OF 29N BETWEEN 74W-79W...AND ALONG A LINE FROM 28N73W TO 31N66W. A WEAK 1018 MB HIGH IS CENTERED NEAR 28N67W PROVIDING FAIR WEATHER ACROSS MUCH OF THE BAHAMAS. AN UPPER LEVEL RIDGE CENTERED NEAR 26N75W SUPPORTS THE SURFACE RIDGE. TO THE E...TWO LOW PRESSURE SYSTEMS ARE IMPACTING THE AREA BETWEEN 50W-65W. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS ON EACH OF THESE. ACROSS THE ERN ATLC...BROAD SURFACE RIDGING DOMINATES ANCHORED BY A 1025 MB HIGH NEAR 33N40W PROVIDING FAIR WEATHER OVER THE REMAINDER OF THE AREA. ALOFT...AN UPPER LEVEL RIDGE IS CENTERED NEAR 21N51W. AN UPPER LEVEL TROUGH IS CENTERED TO THE E NEAR 28N27W. VISIBLE SATELLITE IMAGERY ALSO INDICATES A BROAD AREA OF AFRICAN DUST EXTENDING E OF THE TWO SURFACE LOW PRESSURE SYSTEMS TO THE AFRICAN COAST. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON