000 AXPZ20 KNHC 290845 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC TUE SEP 29 2015 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 0830 UTC. ...SPECIAL FEATURES... TROPICAL STORM MARTY CENTERED NEAR 16.4N 101.7W AT 29/0900 UTC OR 78 NM S OF ZIHUATANEJO MEXICO AND 109 NM WSW OF ACAPULCO MEXICO MOVING E AT 2 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 993 MB. MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65 KT. NUMEROUS MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 75 NM IN THE N QUADRANT. SCATTERED MODERATE CONVECTION IS ELSEWHERE WITHIN 240 NM IN THE E SEMICIRCLE. MARTY IS WEAKENING AND WILL CONTINUE TO DO SO BECOMING A TROPICAL DEPRESSION BY WED AFTERNOON...AND THEN A POST-TROPICAL REMNANT LOW THU NIGHT BEFORE DISSIPATING FRI NIGHT. HEAVY RAINFALL WILL RESULT IN LIFE- THREATENING FLASH FLOODS AND MUD SLIDES...LARGE SWELLS WILL CONTINUE TO IMPACT THE COAST OF SOUTHERN MEXICO RESULTING IN LIFE-THREATENING RIP CURRENTS AND DANGEROUS SURF...AND STORM SURGE IS EXPECTED TO PRODUCE COASTAL FLOODING IN AREAS OF ONSHORE FLOW. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP2/WTPZ22 KNHC FOR MORE DETAILS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM 07N78W TO 09N88W TO 08N102W THEN CONTINUES FROM 15N104W TO LOW PRES NEAR 12N119.5W TO 06N128W TO 13N140W. NO ITCZ AXIS PRESENT. SCATTERED MODERATE CONVECTION IS FROM 05N TO 09N BETWEEN 95W AND 99W...WITHIN 120 NM S OF THE AXIS BETWEEN 107W AND 117W AND ALSO BETWEEN 120W AND 135W...AND W OF 138W. ALSO...SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 180 NM SW OF THE COAST OF CENTRAL AMERICA BETWEEN 80W AND 89W. ...DISCUSSION... SURFACE LOW PRES AT 1008 MB IS NEAR 12N119.5W. FRESH TO STRONG WINDS ARE WITHIN 180 NM IN THE SE QUADRANT OF THE LOW. THE LOW WILL MOVE TO NEAR 14N117W BY 24 HOURS...AND THEN TO NEAR 13N116W BY 48 HOURS. A LARGE AREA OF CROSS EQUATORIAL SOUTHERLY SWELL IS MIXING WITH LONG PERIOD NW SWELL...RESULTING IN COMBINED SEAS OF 7-10 FT ACROSS THE S CENTRAL WATERS. GLOBAL MODEL GUIDANCE FORECASTS THE LOW TO MOVE NE DURING THE LATER PART OF THE WEEK IN THE GENERAL DIRECTION OF THE SOUTHERN BAJA CALIFORNIA PENINSULA. A 1014 MB SURFACE HIGH IS NEAR 30N125W WITH A BROAD RIDGE AXIS EXTENDING TO THE SE TO 20N118W. A 1010 MB OCCLUDED LOW IS CENTERED NW OF THE HIGH NEAR 33N134W WITH A TRAILING STATIONARY FRONT EXTENDING FROM 30N129W TO 22N140W. WINDS W OF THE FRONT ARE 15-20 KT AND ASSOCIATED SWELL OF 8-9 FT IS IN THE FAR NW CORNER OF THE DISCUSSION WATERS. THE LOW AND FRONT WILL BOTH GRADUALLY WEAKEN DURING THE NEXT 24-48 HOURS AND SEAS WILL SUBSIDE TO LESS THAN 8 FT LATER TODAY. THE PRES GRADIENT SW-W OF THE BAJA CALIFORNIA PENINSULA WILL TIGHTEN AS RIDGING SLIDES EASTWARD TOWARD THE PENINSULA AND WITH DEEPENING LOW PRES TROUGHING ACROSS THE GULF OF CALIFORNIA REGION. THIS WILL RESULT IN WINDS INCREASING TO FRESH W OF THE PENINSULA. FRESH NW SWELL WILL COMBINE WITH SE SWELL GENERATED BY MARTY TO RESULT IN 8-9 FT SEAS BY LATE WED NIGHT. GULF OF TEHUANTEPEC...THE LOCAL PRES GRADIENT IS FORECAST TO TIGHTEN ACROSS THE AREA AS HIGH PRES AND ASSOCIATED RIDGING SETS UP ACROSS EASTERN MEXICO. THIS WILL RESULT IN A SURGE OF FRESH TO STRONG NORTHERLY WINDS IN THE GULF BY WED NIGHT. SEAS WILL BUILD TO 8-10 FT BY LATE WED NIGHT AS A RESULT. $$ LEWITSKY