000 AXPZ20 KNHC 260319 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC WED SEP 26 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0230 UTC. ...SPECIAL FEATURES... HURRICANE MIRIAM CENTERED NEAR 19.1N 115.2W AT 26/0300 UTC MOVING TOWARD THE NW OR 310 DEG AT 4 KT. MAXIMUM SUSTAINED WIND SPEED IS 70 KT WITH GUSTS TO 85 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 983 MB. SCATTERED TO NUMEROUS STRONG CONVECTION WAS WITHIN 150 NM NW AND 180 NM SE SEMICIRCLES WHILE SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS ELSEWHERE WITHIN 210 NM N SEMICIRCLE. THIS CONVECTION HAS DECREASED CONSIDERABLY IN THE PAST 6-12 HOURS AS MIRIAM HAS BEGUN TO ENCOUNTER SWLY MIDDLE TO UPPER LEVEL WIND SHEAR. AS MIRIAM BEGINS TO TURN MORE N-NW TONIGHT AND CONTINUE ON THAT COURSE THROUGH EARLY THU...SLOW AND GRADUAL WEAKENING IS FORECAST. LONG PERIOD SWELL GENERATED BY MIRIAM WILL CONTINUE TO AFFECT THE SOUTH AND WEST COASTS OF THE SOUTHERN BAJA PENINSULA DURING THE NEXT COUPLE OF DAYS...AND THE W COAST OF MEXICO FROM ACAPULCO INTO THE SOUTHERN GULF OF CALIFORNIA. THESE SWELLS ARE LIKELY TO CAUSE STRONG AND POWERFUL SURF LEADING TO DANGEROUS AND POTENTIALLY LIFE THREATENING 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 COLOMBIA NEAR 08N76W TO 10N85W TO 11.5N96W TO LOW PRES NEAR 11.5N103.5W 1007 MB TO 11N109W...WHERE IT FRACTURES...THEN RESUMES FROM S OF MIRIAM NEAR 15N115W TO 12.5N129W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING ON TO BEYOND 11N140W. SCATTERED MODERATE ISOLATED STRONG S OF TROUGH TO 05.5N E OF 94W. SCATTERED MODERATE TO STRONG FROM 07N TO 14N BETWEEN 96W AND 111W. ...DISCUSSION... UPPER LEVEL RIDGING EXTENDS NEARLY E TO W ALONG 16-18N AND FROM 07N TO 26N...BETWEEN OLD MEXICO AND 144W...WITH TWO DISTINCT ANTICYCLONIC CIRCULATIONS ON EACH END OF RIDGE. PROGRESSIVE WLY UPPER LEVEL FLOW GENERALLY PREVAILS N OF THE RIDGE...WITH A MIDDLE TO UPPER LEVEL S/W SINKING E-SE IN BETWEEN THE TWO ANTICYCLONES ALONG 121W. A MIDDLE LEVEL CYCLONE WITHIN THE S/W IS NOTED IN WATER VAPOR IMAGERY NEAR 25N121W...AND HAS BEGUN TO PRODUCE MODEST BUT DEEP LAYERED SWLY WIND SHEAR UPON MIRIAM...AS MENTIONED ABOVE. S OF 15N AND E OF 110W...NELY WINDS TO 45 KT PREVAIL ACROSS THE SE QUADRANT OF THE UPPER RIDGE...AND ARE PROVIDING A FAVORABLE ENVIRONMENT FOR CONTINUED DEEP CONVECTION ALONG AND NEAR THE MONSOON TROUGH THERE. OTHERWISE STRONG SUBSIDENCE WITH DRY AND STABLE AT THE MIDDLE AND UPPER LEVELS IS ACROSS THE AREA N OF 16N W OF 120W. A 1025 HIGH CENTERED NEAR 36N140W EXTENDS A RIDGE ACROSS NW PORTIONS TO NEAR 25N124W. AN AREA OF 20 KT TRADE WINDS ON THE SOUTHERN PERIPHERY OF THE RIDGE WAS IDENTIFIED BY AFTERNOON SCATTEROMETER PASSES FROM 13N TO 17N BETWEEN 128W AND 138W...WHERE SEAS ARE RUNNING 8-10 FT IN MIXED NW SWELL AND BUILDING WIND WAVES. THE AERIAL EXTENT OF THE FRESH TRADES WILL DECREASE DURING THE NEXT 24 HOURS AS HIGH PRES MOVES WWD AND WEAKENS. A PERTURBATION OR WAVE HAS DEVELOPED ALONG THE MONSOON TROUGH IN THE VICINITY OF 102W...WHERE A 1009 MB SURFACE LOW IS FOUND ALONG THE TROUGH ABUNDANT TROPICAL MOISTURE IS CONVERGING AROUND A BROAD LOW LEVEL CYCLONIC CIRCULATION THERE BETWEEN 97W AND 110W...AND WILL REMAIN ACTIVE CONVECTIVELY FOR THE NEXT 24-36 HOURS. TWO SWELL EVENTS PLUS SEAS GENERATED BY HURRICANE MIRIAM ARE IMPACTING THE REGIONAL WATERS. MODERATE TO LARGE LONG PERIOD SWELLS FROM THE NW ARE SPREADING ACROSS THE NW WATERS...RAISING SEAS TO 7-9 FT TO THE W AND NW OF MIRIAM. MEANWHILE...A NEW PULSE OF CROSS EQUATORIAL SW SWELLS HAS MOVED THROUGH SE PORTIONS AND REACHED THE COAST OF MEXICO AND CENTRAL AMERICA THIS AFTERNOON AND EVENING...WITH ANOTHER STRONG PULSE TO FOLLOW ON WED AND WED NIGHT. THESE SWELLS WILL MERGE THIS EVENING AND TONIGHT TO PRODUCE SEAS OF 8 TO 11 FT AFFECTING MOST OF THE FORECAST WATERS W OF 105W. SWELLS GENERATED BY HURRICANE MIRIAM WILL CONTINUE TO REACH THE COASTS OF MEXICO TO PRODUCE STRONG AND LARGE SURF AND DANGEROUS RIP CURRENTS WITHIN THE SURF ZONE FROM THE SOUTH HALF OF BAJA CALIFORNIA TO NEAR ACAPULCO. SOUTHERLY SWELL FROM MIRIAM HAS MOVED THROUGH THE ENTRANCE INTO THE GULF OF CALIFORNIA THIS AFTERNOON AND EVENING AND WILL CREATE SIMILAR CONDITIONS ALONG EXPOSED COASTLINES S OF 26N THROUGH WED. $$ STRIPLING