000 AXPZ20 KNHC 250940 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC TUE SEP 25 2012 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0845 UTC. ...SPECIAL FEATURES... HURRICANE MIRIAM CENTERED NEAR 18.7N 114.3W AT 25/0900 UTC MOVING TOWARD THE NW OR 310 DEGREES AT 5 KT. A GRADUAL TURN TO THE NORTH-NORTHWEST IS EXPECTED LATER TODAY...FOLLOWED BY A TURN TO THE NORTH ON WEDNESDAY. ESTIMATED MINIMUM CENTRAL PRESSURE IS 968 MB. MIRIAM IS STILL A CATEGORY TWO HURRICANE ON THE SAFFIR- SIMPSON SCALE. MAXIMUM SUSTAINED WIND SPEED IS 90 KT WITH GUSTS TO 110 KT. SLOW WEAKENING IS FORECAST DURING THE NEXT 48 HOURS AS SOUTHWESTERLY SHEAR INCREASES. SWELLS GENERATED BY MIRIAM WILL AFFECT THE SOUTH AND WEST COASTS OF THE SOUTHERN BAJA PENINSULA DURING THE NEXT COUPLE OF DAYS. THESE SWELLS ARE LIKELY TO CAUSE LIFE-THREATENING SURF AND RIP CURRENT CONDITIONS. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP3/WTPZ23 KNHC FOR MORE DETAILS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH EXTENDS FROM 09N85W TO 11N97W TO 12N106W...THEN RESUMES FROM 13N118W TO 11N128W THEN ITCZ TO BEYOND 09N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS WITHIN 150 NM S OF TROUGH BETWEEN 82W AND 87W. ISOLATED MODERATE TO STRONG CONVECTION IS BETWEEN THE MONSOON TROUGH AND THE COAST OF MEXICO FROM 95W TO 102W. NUMEROUS MODERATE ISOLATED STRONG CONVECTION IS NOTED FROM 08N TO 10N W OF 137W. ...DISCUSSION... ALOFT...A WELL DEFINED UPPER LEVEL CYCLONE IS NEAR 33N144W. SWLY FLOW AHEAD OF THIS SYSTEM CONTINUES TO ADVECT MID TO UPPER LEVEL MOISTURE FROM THE DEEP TROPICS INTO THE NW CORNER OF THE FORECAST REGION. AN ANTICYCLONIC CIRCULATION IS NOW CENTERED NEAR MANZANILLO MEXICO EXTENDING A RIDGE BETWEEN 85W AND 112W. ANOTHER ANTICYCLONE IS LOCATED NEAR 17N132W. A NEARLY ZONAL FLOW DOMINATES THE WATERS N OF 23N E OF 130W. AT LOW LEVELS...A 1027 MB HIGH PRES SITUATED NEAR 36N138W EXTENDS A RIDGE ACROSS THE N WATERS TO NEAR 23N120W. RECENT SCATTEROMETER DATA INDICATE THE PRESENCE OF AN AREA OF FRESH TRADE WINDS ON THE SOUTHERN PERIPHERY OF THE RIDGE...MAINLY FROM 15N TO 19N W OF 128W. THE AERIAL EXTENT OF THE TRADES WILL DECREASE IN ABOUT 24 HOURS AS HIGH PRES MOVES WWD AND SLIGHTLY WEAKENS. TWO SWELL EVENTS PLUS SEAS GENERATED BY HURRICANE MIRIAM ARE IMPACTING THE REGIONAL WATERS. LARGE AND LONG PERIOD SWELLS FROM THE NW ARE SPREADING ACROSS THE NW WATERS RAISING SEAS TO AROUND 9 FT MAINLY W OF A LINE FROM 30N120W TO 15N128W TO 08N140W. CROSS EQUATORIAL SW SWELLS ARE REACHING THE COAST OF MEXICO PARTICULARLY E OF 105W. THESE SWELL EVENTS WILL MERGE TODAY WITH SEAS OF 8 TO 11 FT AFFECTING MOST OF THE FORECAST WATERS W OF 105W...EXCEPT HIGHER ASSOCIATED WITH HURRICANE MIRIAM. SCATTEROMETER DATA SHOWED NLY WINDS OF 20 KT THROUGH THE GULF OF TEHUANTEPEC. THESE WINDS ARE EXPECTED TO DIMINISH BELOW 20 KT TODAY. $$ GR