000 AXNT20 KNHC 201159 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURES... TROPICAL STORM NADINE IS CENTERED NEAR 36.8N 30.6W AT 20/1200 UTC OR ABOUT 155 NM S OF FLORES IN THE AZORES MOVING ESE AT 8 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 983 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SCATTERED MODERATE CONVECTION IS FROM 36N-41N BETWEEN 27W-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 1008 MB SURFACE LOW NEARLY COLLOCATED WITH THE UPPER LEVEL LOW NEAR 31N52W. A SURFACE TROUGH EXTENDS SW FROM THE LOW FROM 29N51W TO 25N55W TO 24N65W. THE CIRCULATION OF THE LOW HAS GRADUALLY BECOME BETTER DEFINED OVER THE PAST 24 TO 36 HOURS AND CONTINUES TO ORGANIZE. THIS SYSTEM HAS A MEDIUM CHANCE OF BECOMING A SUBTROPICAL CYCLONE DURING THE NEXT 48 HOURS. WIDELY SCATTERED MODERATE CONVECTION IS FROM 28N-36N BETWEEN 46W-57W. ISOLATED MODERATE CONVECTION IS ELSEWHERE FROM 23N-30N BETWEEN 43W-54W. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 11N27W TO 18N27W MOVING W AT 10-15 KT. GLOBAL MODEL DATA INDICATES THE WAVE AXIS COINCIDES WITH A 700 MB TROUGH ALONG 29W AND REMAINS WITHIN AN AREA OF MAXIMUM TOTAL PRECIPITABLE WATER FROM 15N-20N BETWEEN 23W-32W...CENTERED JUST WEST OF THE CAPE VERDE ISLANDS. SCATTERED MODERATE CONVECTION IS FROM 15N-17N BETWEEN 27W-29W. TROPICAL WAVE EXTENDS FROM 10N56W TO 17N54W MOVING W AT 15 KT. THE WAVE REMAINS EMBEDDED WITHIN BROAD LOW-LEVEL CYCLONIC FLOW BETWEEN 52W-58W AND WITHIN AN AREA OF DEEP LAYER MOISTURE AS NOTED ON TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE CONVECTION IS FROM 15N-18N BETWEEN 52W-56W. TROPICAL WAVE EXTENDS FROM 15N76W TO 23N75W MOVING W AT 10 KT. LOW-LEVEL CYCLONIC FLOW IS EVIDENT ACROSS THE CENTRAL CARIBBEAN AND GLOBAL MODEL DATA INDICATES 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 ASSOCIATED WITH THE WAVE ARE QUICKLY BECOMING ABSORBED INTO A VERY MOIST AIRMASS OVER THE SW NORTH ATLC...CUBA...AND EASTERN GULF OF MEXICO. WIDELY SCATTERED MODERATE CONVECTION IS FROM 15N-20N BETWEEN 75W-80W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 17N16W TO 05N38W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 05N38W TO 02N50W. ISOLATED MODERATE CONVECTION IS FROM 04N-09N BETWEEN 11W-28W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 05N-08N BETWEEN 40W-47W. ...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 STATIONARY FRONT ANALYZED FROM THE NORTHERN FLORIDA PENINSULA NEAR 29N82W TO 27N86W DISSIPATING TO 21N92W. 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 20N96W. THE MOST INTENSE CONVECTION IS LOCATED SOUTH AND EAST OF THE STATIONARY FRONT FROM 21N-24N BETWEEN 85W-92W. 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 23N75W AND PROVIDES INFLUENCE SOUTHWARD ACROSS MUCH OF THE CARIBBEAN. WEST OF THE RIDGE AXIS ALONG 73W...MIDDLE TO UPPER LEVEL DIFFLUENCE REMAINS MAXIMIZED BETWEEN THE TROUGH AND RIDGE WITH A WEAK UPPER LEVEL LOW CENTERED NEAR 21N81W 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 17N BETWEEN 78W-87W...INCLUDING INLAND PORTIONS OF CENTRAL CUBA. FARTHER EAST...BENEATH THE HEART OF THE UPPER LEVEL ANTICYCLONE...A TROPICAL WAVE IS ALONG 76W AND WITH AN ALREADY OVERALL DIFFLUENT ENVIRONMENT IN PLACE OVER THE CENTRAL CARIBBEAN...ISOLATED SHOWERS AND TSTMS ARE OCCURRING FROM 15N-20N BETWEEN 75W-80W. FINALLY EAST OF THE UPPER LEVEL RIDGE AXIS...OUTSIDE OF THE ISOLATED CONVECTION ASSOCIATED WITH THE TROPICAL WAVE...AN UPPER LEVEL LOW IS CENTERED EAST OF THE LESSER ANTILLES NEAR 16N57W THAT IS PROVIDING NORTHERLY WINDS ALOFT AND GENERALLY FAIR CONDITIONS ACROSS THE LESSER ANTILLES THIS MORNING. ATLANTIC OCEAN... A MIDDLE TO UPPER LEVEL TROUGH IS ACROSS THE EASTERN CONUS AND SUPPORTS A STATIONARY FRONT ANALYZED FROM 32N76W TO THE NORTHERN FLORIDA PENINSULA NEAR 29N82W. WATER VAPOR IMAGERY INDICATES DEEP LAYERED MOISTURE ADVECTION FROM THE NORTHWESTERN CARIBBEAN SEA NORTH-NORTHEASTWARD TO THE CANADIAN MARITIMES OF NOVA SCOTIA AND NEWFOUNDLAND THAT SUPPORTS SCATTERED SHOWERS AND ISOLATED TSTMS MOSTLY WEST OF 74W. THE REMAINDER OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF WEAK SURFACE RIDGING WITH AXIS EXTENDING FROM WEST OF BERMUDA NEAR 32N66W TO THE CENTRAL BAHAMAS NEAR 26N74W. FARTHER EAST OVER THE CENTRAL ATLC...THE SPECIAL FEATURES LOW CONTINUES TO INFLUENCE THE AREA N OF 20N BETWEEN 43W-60W. ALSO...CYCLONIC WINDS AND CONVECTION ASSOCIATED WITH TROPICAL STORM NADINE ARE LOCATED N OF 30N BETWEEN 20W-38W IMPACTING THE AZORES. ELSEWHERE THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1018 MB HIGH CENTERED NEAR 26N39W. THE SURFACE RIDGE AXIS EXTENDS FROM THE HIGH CENTER EASTWARD TO THE CANARY ISLANDS THEN NORTHEASTWARD TO THE MADEIRA ISLANDS NEAR 33N16W. 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