000 AXPZ20 KNHC 310921 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 517 UTC Sun Dec 31 2017 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 0900 UTC. ..SPECIAL FEATURES... Gale Warning: A cold front is moving through the NW corner of the area, extending from 30N134W to 21N140W. Overnight scatterometer pass depicts fresh to strong winds prevail N of 28N within 60 nm east of the front. This front will slowly move eastward while weakening. Deepening low pressure will move into the NW waters tonight into Monday. The pressure gradient between this deepening low and high pressure west of the area will help for winds to increase to gale force over the far NW waters N of 28N and west of 135W. Winds will diminish below gale force on Monday as high pressure west of the area weakens and the pressure gradient loosens. This event will usher in a fresh set of NW swell into the area. Seas will peak near 20 ft during the period of gale force winds and will slowly subside afterwards while propagating southeast across the forecast waters. By midweek, seas 8 ft or greater associated to this swell will cover much of the forecast waters north of 10N and west of 120W. Refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. Gulf of Tehuantepec Gale Warning: Winds and seas will briefly fall below advisory criteria today. A cold front has moved into the far northern Gulf of Mexico. A reinforcing front will push into the northern Gulf of Mexico tonight. The front will shift across the Gulf of Mexico, reaching the Bay of Campeche Monday night. Strong high pressure behind the cold front will induce the next gale force gap wind event in the Gulf of Tehuantepec. This next event has the potential to be a strong and long-lasting event, with gale force winds persisting for much of the next 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 09N82W to 06N91W to 06N97W. The ITCZ extends from 06N97W to 08N105W to 09N127W. It resumes from 09N133W to beyond 08N140W. Scattered moderate isolated strong convection was noted from 05N to 09N between 82W and 86W. Scattered moderate isolated strong convection was noted within 120 nm north of the ITCZ between 107W and 120W. ...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. NW swell will propagate into the waters off Baja California Norte Thu, building seas to 6 to 8 ft. Elsewhere, tranquil marine conditions are expected 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. 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 next 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... Please see special features section above for more details about gale force winds in the NW corner of the forecast area, and associated swell. A surface trough along 130W and south of 20N will persist and shift northward through Tue ahead of an advancing cold front in the NW waters. Strong winds and seas to 8 ft are expected with the associated surface trough by Mon as it moves northward, extending from 26N127W to 21N130W. Winds associated to this trough will diminish to 20 kt or less Tuesday, while seas to 8 ft merge with NW swell propagating across the area. $$ AL