000 AXPZ20 KNHC 242204 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2204 UTC Sat Sep 24 2016 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 2100 UTC. ...SPECIAL FEATURES... A large low pressure area, analyzed as a 1006 mb low pressure near 13N119W is showing slightly more organized shower and thunderstorms activity. Satellite images indicate that the low's circulation, although still broad, is gradually becoming better defined, and a band of moderate to isolated strong convection is seen within about 60 nm of a line from 12N123W to 16N119W. Currently, the pressure gradient is supporting strong southwest winds within 120 nm in the southeast semicircle of low center with seas of 8 to 9 ft. Convergence of these winds is supporting another area of scattered moderate to isolated strong convection from 11N to 17N between 110W and 118W. Environmental conditions are conducive for a tropical depression to form during the next day or two. This disturbance is expected to move slowly northward during the next few days. A gale warning is already in effect in association with this feature beginning on Sunday morning. Please refer to the latest Graphical Tropical Weather Outlook for more information at http://hurricanes.gov. ...TROPICAL WAVES... A tropical wave is analyzed north of 10N along 95W. The axis crosses the Gulf of Tehuantepec. This is enhancing convection off the coasts of southern Mexico and Guatemala mainly at night. Expect the wave to gradually lose identity over the next couple of days. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 11N86W to 12N95W to 10N105W, resuming at the 1006 mb low pressure area near 13N119W and continuing to 1009 mb low pressure near 12N135W to beyond 11N140W. Scattered moderate convection within 120 nm north and 90 nm south of the axis between 90W and 97W. Scattered moderate within 120 nm either side of the monsoon trough axis between 127W and 137W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gentle to moderate breezes continue across the region north of 20N between the subtropical ridge to the west and weak troughing over the Gulf of California. Northerly swell to 8 ft persist off Baja California Norte beyond 200 nm, but will be decaying to below 8 ft through this evening. Building high pressure over the Great Basin to the north of the region will allow a brief surge of fresh to strong northerly winds into the northern Gulf of California early Sunday, diminishing slightly Sunday night, then veering more east to southeast and increasing again on Monday on the tail end of a weak frontal boundary drifting into northern Mexico. A cold front is forecast to move across the Gulf of Mexico waters. High pressure behind the front will likely induce the first Gulf of Tehuantepec gap wind event of the season by late Tuesday into Wednesday morning. At this time, marine guidance suggests northerly winds of 20-25 kt and building seas to 8 ft. Winds will further increase to 25-30 kt Wednesday night into Thursday morning with seas up to 9-10 ft. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Mainly light and variable winds are noted north of the monsoon trough while gentle to locally moderate south to southwest flow is expected south of monsoon trough through early next week. Combined seas of 4 to 7 ft will continue today primarily in long- period southwest swell, then subside to 4 to 5 ft late on Sunday and continuing into early next week. REMAINDER OF THE AREA... A 1009 mb low pressure area is analyzed along the monsoon trough near 12N135W. Expect the low to likely reach 140W on Monday, then will remain near 140W through mid-week. The pressure gradient between this low and the subtropical ridge to the north is resulting in an area of fresh to strong northeast winds within 120 nm to the north of the low pressure center. Seas of 8 to 9 ft in this area is merging with a greater area of 8 ft seas due to northeast swell, reaching as far north as 22N. This area will diminish in areal extent, covering an area from 13N to 20n between 135W and 140W by late Sunday. Seas of 8 to 9 ft will persist from 10N to 15N west of 138W through early next week on the eastern side of the low pressure. $$ CHRISTENSEN