000 AXNT20 KNHC 200547 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT THU SEP 20 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 37.1N 31.0W AT 20/0600 UTC OR ABOUT 140 NM S OF FLORES IN THE AZORES MOVING E AT 3 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 990 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SCATTERED MODERATE CONVECTION IS FROM 37N-39N BETWEEN 31W-34W. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/ WTNT34 AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. AN UPPER LEVEL LOW IS CENTERED NEAR 31N51W AND SUPPORTS A 1010 MB SURFACE LOW NEARLY COLLOCATED WITH THE UPPER LEVEL LOW NEAR 31N52W. A SURFACE TROUGH EXTENDS SW FROM THE LOW CENTERED TO 25N57W. THE CIRCULATION OF THE LOW HAS GRADUALLY BECOME BETTER DEFINED OVER THE PAST 24 HOURS AND CONTINUES TO ORGANIZE. THIS SYSTEM HAS A MEDIUM CHANCE OF BECOMING A SUBTROPICAL CYCLONE DURING THE NEXT 48 HOURS. SCATTERED MODERATE CONVECTION IS FROM 33N-36N BETWEEN 47W-56W WITH WIDELY SCATTERED MODERATE CONVECTION ELSEWHERE FROM 28N-33N BETWEEN 51W-58W. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 12N23W TO 20N25W MOVING W AT 10-15 KT. GLOBAL MODEL DATA INDICATES THE WAVE AXIS COINCIDES WITH A 700 MB TROUGH ALONG 26W AND REMAINS WITHIN AN AREA OF MAXIMUM TOTAL PRECIPITABLE WATER FROM 14N-19N BETWEEN 21W-28W...CENTERED OVER THE CAPE VERDE ISLANDS. WHILE NO SIGNIFICANT DEEP CONVECTION IS NOTED ON SATELLITE IMAGERY...ISOLATED SHOWERS ARE POSSIBLE FROM 14N-22N BETWEEN 18W-31W. TROPICAL WAVE EXTENDS FROM 10N53W TO 19N48W MOVING W AT 10-15 KT. THE WAVE REMAINS EMBEDDED WITHIN BROAD LOW-LEVEL CYCLONIC FLOW BETWEEN 47W-55W AND WITHIN AN AREA OF DEEP LAYER MOISTURE AS NOTED ON TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE CONVECTION IS FROM 16N-20N BETWEEN 47W-52W. SCATTERED SHOWERS ARE ELSEWHERE FROM 11N-21N BETWEEN 47W-56W. TROPICAL WAVE EXTENDS FROM 13N76W TO 21N76W MOVING W AT 10-15 KT. THE WAVE REMAINS DIFFICULT TO TRACK WITH LOW-LEVEL CYCLONIC FLOW EVIDENT ACROSS THE CENTRAL CARIBBEAN AND GLOBAL MODEL DATA INDICATING A WEAK 700 MB TROUGH PROGRESSING WESTWARD ON THE SOUTHERN PERIPHERY OF A MIDDLE TO UPPER LEVEL RIDGE CENTERED OVER THE SW NORTH ATLC REGION. TOTAL PRECIPITABLE WATER IMAGERY INDICATES MAXIMIZED VALUES OVER THE AREA FROM 15N-20N BETWEEN 66W-78W. ISOLATED MODERATE CONVECTION IS FROM 14N-21N BETWEEN 66W-78W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 14N17W TO 06N36W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 06N36W TO 04N51W. ISOLATED MODERATE CONVECTION IS FROM 05N-09N BETWEEN 10W-28W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 04N-08N BETWEEN 41W-46W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM THE UPPER GREAT LAKES REGION SOUTHWARD TO THE LOWER MISSISSIPPI RIVER VALLEY AND OVER MUCH OF THE WESTERN GULF. THE TROUGHING SUPPORTS A COLD FRONT ANALYZED FROM THE CENTRAL FLORIDA PENINSULA NEAR 28N82W TO 26N85W BECOMING STATIONARY INTO THE SW GULF ALONG 24N90W TO 19N92W. LOW-LEVEL MOISTURE CONVERGENCE IN THE VICINITY OF THE FRONT ALONG WITH MIDDLE TO UPPER LEVEL DIFFLUENCE EAST OF THE TROUGH AXIS IS GENERATING SCATTERED SHOWERS AND TSTMS EAST OF A LINE FROM THE FLORIDA PANHANDLE NEAR 30N85W TO 20N97W. THE MOST INTENSE CONVECTION IS LOCATED SOUTH AND EAST OF THE STATIONARY FRONT FROM 21N-25N BETWEEN 80W-91W. THE FRONT IS FORECAST TO BECOME MORE AND MORE DIFFUSE THROUGH FRIDAY AS SURFACE HIGH PRESSURE REMAINS ANCHORED OVER THE SE CONUS. CARIBBEAN SEA... WHILE A MIDDLE TO UPPER LEVEL TROUGH IS OVER THE GULF OF MEXICO...AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED NORTH OF EASTERN CUBA NEAR 23N74W AND PROVIDES INFLUENCE ACROSS MUCH OF THE CARIBBEAN. WEST OF THE RIDGE AXIS ALONG 73W...MIDDLE TO UPPER LEVEL DIFFLUENCE REMAINS MAXIMIZED BETWEEN THE TWO FEATURES WITH A WEAK UPPER LEVEL LOW CENTERED NEAR 20N82W EMBEDDED WITHIN THE RIDGE AND MOVING NORTHWESTWARD INTO THE LARGER MEAN TROUGHING OVER THE GULF OF MEXICO. SCATTERED SHOWERS AND TSTMS ARE OCCURRING IN RESPONSE N OF 19N BETWEEN 78W-87W... INCLUDING INLAND PORTIONS OF WESTERN CUBA. FARTHER EAST... BENEATH THE HEART OF THE UPPER LEVEL ANTICYCLONE...A TROPICAL WAVE IS ALONG 77W AND WITH AN ALREADY OVERALL DIFFLUENT ENVIRONMENT IN PLACE OVER THE CENTRAL CARIBBEAN...ISOLATED SHOWERS AND TSTMS ARE OCCURRING FROM 14N-21N BETWEEN 66W-78W. FINALLY EAST OF THE UPPER LEVEL RIDGE AXIS...OUTSIDE OF THE ISOLATED CONVECTION ASSOCIATED WITH THE TROPICAL WAVE... CONDITIONS ARE EXPECTED TO IMPROVE AS MOSTLY CLEAR SKIES AND NORTHERLY WINDS ALOFT PROVIDE AN OVERALL STABLE ENVIRONMENT ACROSS THE LESSER ANTILLES. ATLANTIC OCEAN... A MIDDLE TO UPPER LEVEL TROUGH IS ACROSS THE EASTERN CONUS AND SUPPORTS A COLD FRONT ANALYZED FROM 32N76W TO THE CENTRAL FLORIDA PENINSULA NEAR CAPE CANAVERAL. WATER VAPOR IMAGERY INDICATES DEEP LAYERED MOISTURE ADVECTION FROM THE WESTERN CARIBBEAN SEA NORTH-NORTHEASTWARD TO THE CANADIAN MARITIMES OF NOVA SCOTIA AND NEWFOUNDLAND THAT SUPPORTS SCATTERED SHOWERS AND ISOLATED TSTMS MOSTLY WEST OF 75W. THE REMAINDER OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF A WEAK SURFACE RIDGE WITH AXIS EXTENDING FROM BERMUDA NEAR 32N65W TO THE CENTRAL BAHAMAS NEAR 25N75W. FARTHER EAST OVER THE CENTRAL ATLC...THE SPECIAL FEATURES LOW CONTINUES TO INFLUENCE THE AREA N OF 20N BETWEEN 45W-60W. ALSO...CYCLONIC WINDS AND CONVECTION ASSOCIATED WITH TROPICAL STORM NADINE ARE LOCATED N OF 30N BETWEEN 20W-38W IMPACTING THE AZORES THROUGH THE OVERNIGHT HOURS. ELSEWHERE THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1019 MB HIGH CENTERED NEAR 25N37W. 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