000 AXPZ20 KNHC 272215 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC THU SEP 27 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2115 UTC. ...SPECIAL FEATURES... MIRIAM...CENTERED NEAR 22.1N 116.9W AT 27/2100 UTC MOVING W AT 4 KT...HAS JUST BEN DOWNGRADED TO A TROPICAL DEPRESSION. MAXIMUM SUSTAINED WINDS NOW 30 KT GUSTS 40 KT AND ESTIMATED MINIMUM CENTRAL PRESSURE 1000 MB. CONVECTION ASSOCIATED WITH MIRIAM HAS BECOMING COMPLETELY OBLITERATED BY THE MID TO UPPER LEVEL TROUGH SWEEPING SLOWLY ACROSS THE VICINITY IN THE PAST 24 HOURS...AND ALL THAT REMAINS OF MIRIAM IS A WELL DEFINED LOW LEVEL CLOUD SWIRL ABOUT 150 NM IN DIAMETER. MIRIAM IS EMBEDDED WITHIN AN ELONGATED AND SOMEWHAT TRIANGULAR SHAPED CYCLONIC CIRCULATION OF THE LOWER TROPOSPHERE...AND WILL GRADUALLY SPIN DOWN WITHIN THIS CIRCULATION WITHIN 72 HOURS. SEAS SURROUNDING MIRIAM ARE EXPECTED TO FALL BELOW 12 FT WITHIN THE NEXT 12-18 HOURS. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP3/WTPZ23 KNHC FOR MORE DETAILS. A DEVELOPING AREA OF LOW PRESSURE EMBEDDED WITHIN THE MONSOON TROUGH WAS CENTERED NEAR 16.5N107W WITH AN ESTIMATED PRESSURE OF 1007 MB. THIS FEATURE HAS TRACKED NW DURING THE PAST 24 HOURS AND HAS BECOME CAPTURED ON THE EASTERN FLANKS OF THE ELONGATED N TO S ALIGNED CYCLONIC CIRCULATION MENTIONED ABOVE WITH MIRIAM. STRONG S TO S-SE LOW LEVEL WIND FLOW IS EXPECTED TO TRANSPORT THIS EMBEDDED LOW CENTER N-NW TOWARDS THE S TIP OF BAJA CALIFORNIA AND THE SOUTHERN ENTRANCE INTO THE GULF OF CALIFORNIA DURING THE NEXT 24 HOURS. ASSOCIATED MAINLY SLY WINDS OF 20 TO 30 KT WITH GUSTS TO GALE FORCE WILL ACCOMPANY THIS LOW DURING THIS TIME...WITH ASSOCIATED SEAS 8 TO 12 FT. SATELLITE IMAGERY THIS AFTERNOON SHOWS CONVECTION OCCURRING ALONG AND TO THE SE OF THE MONSOON TROUGH...EXTENDING FROM NEAR 10N132W SPIRALING NE THEN N TO THIS DEVELOPING LOW...WITH STRONG SLY FLOW CONTINUING NWD TO THE ENTRANCE INTO THE GULF OF CALIFORNIA. SCATTERED TO LOCALLY NUMEROUS MODERATE TO STRONG CONVECTION PREVAILS ALONG THIS ZONE OF STRONG MONSOON FLOW...AND WILL CONTINUE TO SPREAD NWD INTO S PORTIONS OF THE GULF OF CALIFORNIA...THE SOUTHERN BAJA PENINSULA...AND COASTAL MEXICO ADJACENT TO THE GULF. SQUALLS WITH WIND GUSTS IN EXCESS OF GALE FORCE CAN BE EXPECTED...AND WITH SCATTERED THUNDERSTORMS PRODUCING VERY HEAVY RAINFALL. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH FROM 10N79W TO LOW PRES NEAR 09N94W 1010 MB TO 12N100W WHERE IT FRACTURES...THEN RESUMES FROM LOW PRES NEAR 16.5N107W 1007 MB TO 16N112W TO 13N116W TO 11N140W. SCATTERED MODERATE ISOLATED STRONG N OF 07.5N BETWEEN 80W AND 86W. SCATTERED MODERATE ISOLATED STRONG WITHIN 210 NM S OF TROUGH BETWEEN 90W AND 101W. SCATTERED MODERATE ISOLATED STRONG FROM 10N TO 16N BETWEEN 106W AND 116W. SCATTERED MODERATE TO STRONG FROM 08.5N TO 11N BETWEEN 129W AND 133W. ...DISCUSSION... SUBTROPICAL HIGH CENTERED NEAR 33N141W 1023 MB EXTENDS A RIDGE SE AND ACROSS THE NW WATERS TO NEAR 29N119W. MODERATE TRADE WINDS ARE NOTED ON THE SOUTHERN PERIPHERY OF THE RIDGE AND W OF 140W BY RECENT SCATTEROMETER PASSES...WITH 7-9 FT SEAS IN MIXED NW SWELL AND NE WIND WAVES. LIGHT TO MODERATE W-SW WINDS ELSEWHERE E OF 105W ARE MAINTAINING A MOIST CONVECTIVELY UNSTABLE REGIME S OF THE TROUGH THAT IS EXPECTED TO REMAIN CONVECTIVELY ACTIVE THE NEXT FEW DAYS AS AN UPPER RIDGE REMAINS IN PLACE OVER THE MONSOON TROUGH AXIS. TWO AREAS OF SWELL MOVING THROUGH THE REGION IN ADDITION TO SEAS GENERATED BY T.S. MIRIAM WILL CONTINUE TO AFFECT THE DISCUSSION AREA THROUGH TONIGHT. MODERATE LONG PERIOD SWELLS ARE SPREADING ACROSS THE WATERS NW OF MIRIAM. WHILE CROSS-EQUATORIAL SW SWELLS MOVING THROUGH SE PORTIONS ARE REACHING THE COAST OF MEXICO AND CENTRAL AMERICA...WITH ANOTHER STRONG PULSE TO FOLLOW TONIGHT... MERGING WITH 8-10 FT SEAS W OF 105W. SWELLS GENERATED BY MIRIAM AFFECTING COASTS OF THE SOUTH-CENTRAL BAJA PENINSULA WILL CREATE SMALL BUT STRONG SURF ALONG EXPOSED COASTLINES S OF 27N THROUGH THIS EVENING. ADDITIONAL PULSES OF NW SWELL WILL REACH THE NW CORNER OF THE DISCUSSION AREA FRI NIGHT AND SAT...BUILDING SEAS TO 9 FT. $$ STRIPLING