000 AXPZ20 KNHC 011424 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1530 UTC Mon Jan 1 2018 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ..SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Winds and seas will increase over the Gulf of Tehuantepec today as strong high pressure building behind a cold front moving across the Gulf of Mexico helps tighten the pressure gradient over the forecast area. Winds will increase further to gale force over the Gulf of Tehuantepec by late today. This gale event is expected to be strong and long- lasting, with gale force winds persisting for much of the week, and peaking near 45 kt. Swell associated to this event will push downstream of the Gulf of Tehuantepec, with seas 8 ft or greater reaching as far south as 05N and west to 105W by midweek. Refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 1012 mb low pressure near 05N79W to 06N100W. The intertropical convergence zone continues from 06N100W to 11N120W, and resumes from 11N130W to beyond 06.5N140W. Scattered moderate convection was noted from 03N to 05N between 78W and 82W. Scattered moderate to isolated strong convection was noted from 09N to 13N between 125W and 130W. Scattered moderate convection was also observed from 20N to 24N between 121W and 124W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see special features section above for more details about the upcoming gale force gap wind event in the Gulf of Tehuantepec. Relatively tranquil marine conditions will persist through the week with light to gentle winds prevailing across the forecast waters. Seas in the range of 3 to 5 ft will continue in the offshore waters, while seas in the 1 to 3 ft range will prevail in the Gulf of California. NW swell of 6 to 8 ft will propagate into the waters off Baja California Norte later in the week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... NE winds will pulse to fresh to strong in the Gulf of Papagayo through the middle of the week. Winds will further increase to near gale force Thursday as high pressure builds north of the area. Light to gentle NE to E winds will prevail elsewhere N of 09N, with gentle to moderate S to SW winds expected S of 09N. REMAINDER OF THE AREA... A 1008 mb low pressure is centered near 27.5N138W. An associate sharp upper trough along 135W is supporting scattered showers and thunderstorms are noted within 120 nm of the low pressure, and along a pair of merging cold front to the east of the low pressure. The same upper trough is also supporting scattered showers and thunderstorms farther south along the ITCZ from 09N to 13N between 125W and 130W. An earlier scatterometer satellite pass indicated a large area of winds to just below gale force to the west of the low pressure. The low pressure is slowly weakening and drifting northeast and the earlier gale warning has been allowed to expire as a result. Strong winds west of the low will diminish to 20 kt or less over the next 24 hours. Moderately high seas to 17 ft will subside through tonight, with mainly NW swell of 8 to 11 ft lingering over the waters north of 18N and west of 135W through Tue. The swell will spread farther east through mid week, with seas 8 to 9 ft covering most of the area north of 12N and west of 125W by late Wed. The merging cold fronts will continue east before stalling and eventually dissipating through mid week. Meanwhile, an earlier scatterometer satellite pass confirmed strong winds near a surface trough reaching from 21N130W to 25N123W. The trough along with the attendant strong winds and seas to 8 ft will drift north ahead of the merging cold fronts late today. Winds will diminish by late afternoon, with the shorter period SE wind waves mixing with the longer period NW swell over the area north of 25N between 125W and 130W. $$ Christensen