000 AXNT20 KNHC 180539 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT TUE SEP 18 2012 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...SPECIAL FEATURES... TROPICAL STORM NADINE IS CENTERED NEAR 32.0N 36.4W AT 18/0300 UTC OR ABOUT 425 NM WSW OF THE AZORES MOVING NE AT 8 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 989 MB. MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. SCATTERED MODERATE CONVECTION IS FROM 33N-37N BETWEEN 30W-37W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 09N42W TO 16N36W MOVING W AT 10-15 KT. THE WAVE REMAINS EMBEDDED WITHIN BROAD CYCLONIC FLOW FROM 09N-17N BETWEEN 36W-44W AND WITHIN A SURGE OF DEEP LAYER MOISTURE AS NOTED ON TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE CONVECTION IS FROM 14N-17N BETWEEN 39W-42W. TROPICAL WAVE EXTENDS FROM 11N64W TO 18N62W MOVING W AT 10-15 KT. THE WAVE REMAINS DIFFICULT TO TRACK WITH LOW-LEVEL CYCLONIC FLOW EAST OF THE LESSER ANTILLES BETWEEN 57W-62W AND A WEAK 700 MB TROUGH OVER THE EASTERN CARIBBEAN SEA ALONG 66W. THEREFORE THE POSITION OF THE WAVE IS COMPROMISED BETWEEN THESE TWO FEATURES WITH TOTAL PRECIPITABLE WATER IMAGERY INDICATING MAXIMIZED VALUES FROM 13N-19N BETWEEN 54W-70W. SCATTERED MODERATE CONVECTION IS FROM 12N-15N BETWEEN 56W-60W...WITH ISOLATED SHOWERS AND TSTMS ELSEWHERE ACROSS THE EASTERN CARIBBEAN SEA FROM 13N-20N BETWEEN 60W-70W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N17W TO 09N34W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 09N45W TO 08N50W TO 10N61W. SCATTERED MODERATE CONVECTION IS FROM 03N-08N BETWEEN 23W-31W...AND FROM 07N-10N BETWEEN 46W-53W. ...DISCUSSION... GULF OF MEXICO... AS OF 18/0300 UTC...WATER VAPOR IMAGERY INDICATES A MIDDLE TO UPPER LEVEL SHORTWAVE TROUGH IS LOCATED OVER THE LOWER MISSISSIPPI RIVER VALLEY AND EXTENDS AN AXIS INTO THE WESTERN GULF ALONG 31N92W TO 22N98W. THE TROUGHING SUPPORTS A WEAK COLD FRONT ANALYZED FROM A 1007 MB LOW CENTERED OVER SOUTHERN MISSISSIPPI NEAR 31N90W TO 26N94W NEAR NOAA BUOY 42002. LOW- LEVEL MOISTURE CONVERGENCE IN THE VICINITY OF THE FRONT ALONG WITH MIDDLE TO UPPER LEVEL DIFFLUENCE EAST OF THE TROUGH AXIS IS GENERATING WIDELY SCATTERED SHOWERS AND TSTMS N OF 26N BETWEEN THE FLORIDA PENINSULA AND THE FRONT. GLOBAL MODELS SUGGEST THE SURFACE LOW PRESSURE AREA WILL QUICKLY MOVE NE AND BECOME ABSORBED INTO THE NEXT COLD FRONT CURRENTLY OVER SE OKLAHOMA AND NORTHERN TEXAS PROVIDING THE CENTRAL AND EASTERN GULF WITH CONTINUED SURFACE TROUGHING AND AN UNSETTLED WEATHER PATTERN. THE SECONDARY COLD FRONT IS FORECAST TO STALL AND BECOME STATIONARY OVER THE EASTERN GULF WEDNESDAY INTO THURSDAY WITH INCREASED PROBABILITY OF SHOWER AND TSTM ACTIVITY. ELSEWHERE FOR THE OVERNIGHT HOURS...A FEW ISOLATED SHOWERS AND TSTMS ARE NOTED ACROSS THE SE GULF S OF 24N BETWEEN 80W-90W AND ALONG THE SOUTHERN MEXICO GULF COAST BETWEEN 92W-97W. CARIBBEAN SEA... AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER SOUTHERN GUATEMALA NEAR 15N90W THAT EXTENDS INFLUENCE EAST TO 80W. A DIFFLUENT ENVIRONMENT REMAINS MAXIMIZED OVER PORTIONS OF THE NW CARIBBEAN...CENTRAL AMERICA...AND SOUTHERN MEXICO GENERATING WIDELY SCATTERED SHOWERS AND TSTMS FROM 18N-24N BETWEEN 80W-90W...AND FROM 12N-19N BETWEEN 87W-95W. FARTHER EAST...AN UPPER LEVEL LOW IS CENTERED NEAR 15N77W AND EXTENDS AN INVERTED UPPER LEVEL TROUGH AXIS NORTHWARD FROM THE UPPER LEVEL LOW CENTER TO OVER CENTRAL CUBA NEAR 21N79W. WATER VAPOR IMAGERY INDICATES THAT MOSTLY DRY AIR IS ASSOCIATED WITH THIS FEATURE ACROSS THE CENTRAL CARIBBEAN BETWEEN 72W-81W. SCATTERED SHOWERS AND TSTMS HOWEVER ARE CONFINED S OF 12N BETWEEN 71W-79W IN ASSOCIATION WITH THE PROXIMITY OF THE MONSOON TROUGH AXIS WHICH LIES ALONG 10N FROM COSTA RICA TO NORTHERN COLOMBIA. FINALLY... ACROSS THE EASTERN CARIBBEAN...AS MENTIONED ABOVE...A TROPICAL WAVE IS ALONG 63W AND STRADDLES BETWEEN LOW-LEVEL CYCLONIC FLOW ALONG 59W AND A 700 MB TROUGH OVER PUERTO RICO. ISOLATED SHOWERS AND TSTMS ARE OCCURRING FROM 13N-20N BETWEEN 60W-70W. ATLANTIC OCEAN... AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED NORTH OF PUERTO RICO NEAR 20N66W AND EXTENDS A RIDGE AXIS NW TO 32N79W. WATER VAPOR IMAGERY INDICATES MOST MIDDLE TO UPPER LEVEL MOISTURE IS LOCATED ON THE SOUTHERN AND SOUTHWESTERN PERIPHERY OF THE RIDGE WITH ISOLATED SHOWERS AND TSTMS OCCURRING FROM 18N-22N BETWEEN 60W-75W...AND FROM 22N-30N W OF 75W. THE REMAINDER OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1021 MB HIGH CENTERED WELL NORTH OF THE DISCUSSION AREA NEAR 39N64W. FARTHER EAST...A WEAK UPPER LEVEL TROUGH EXTENDS ALONG 47W TO A BASE NEAR 25N50W AND SUPPORTS A STATIONARY FRONT ANALYZED FROM 32N52W TO 30N54W THEN AS A SURFACE TROUGH TO 24N60W. ISOLATED SHOWERS ARE OCCURRING WITHIN 60 NM EITHER SIDE OF THE BOUNDARY. ASIDE FROM THE CYCLONIC WINDS ASSOCIATED WITH TROPICAL STORM NADINE N OF 25N BETWEEN 27W-45W...THE REMAINDER OF THE EASTERN AND CENTRAL ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1019 MB HIGH CENTERED NEAR 28N23W. THE RIDGE AXIS EXTENDS SW FROM THE HIGH CENTER TO 20N40W THEN W-NW TO 23N50W. 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