000 AXPZ20 KNHC 281554 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Thu Dec 28 2023 Tropical Weather Discussion for the eastern Pacific Ocean from 03.4S to 30N, east of 120W including the Gulf of California, and from the Equator to 30N, between 120W and 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 1530 UTC. ...SPECIAL FEATURES... Gale Warning Far NW Waters and Very Large Swell Event: A cold front will move southeastward across the NW waters today and reach from 30N129W to 22N140W Fri morning. SW gales are expected ahead of the front north of 28N west of 135W today as well as W to NW gales behind the front north of 28N west of 135W tonight. A very large, 16-18 second NW swell associated with the cold front is spreading southeastward and will lead to seas in excess of 12 ft for most waters north of 10N and west of 115W today. A pair of altimeter passes measured seas up to 25 ft near 27N135W at 0600 and 0630 UTC overnight. Reinforcing NW swell will arrive tonight producing a peak around 30 ft seas along our NW corner waters. This will force seas of 12 ft or greater over most of our waters north of 05N west of 115W through Sat night before gradually diminishing early next week. Gulf of Tehuantepec Gale Warning: Winds draining from the Chivela Pass are forcing fresh to locally strong N winds through Fri. By Fri night, a strong cold front pushing across the W Gulf of Mexico will induce a N gale-force gap wind over the Gulf of Tehuantepec. Gales should continue through the weekend before subsiding Sun afternoon. Peak seas during the period of gales will be 10-11 ft. Please refer to the High Seas Forecast, issued by the National Hurricane Center, at https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml, for details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from the Colombia-Panama border near 08N78W to 05N95W. The ITCZ extends from 05N95W to beyond 05N140W. Scattered moderate convection is occurring from 05N-10N between 125W-135W and from 04N-08N east of 89W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features Section above for details on a Gale Warning for the Gulf of Tehuantepec. A 1022 mb high centered near 27N123W with a ridge extending northeastward to S California continues to dominate the offshore waters of Mexico. The pressure gradient between the ridge and lower pressures over Mexico supports moderate to fresh NW winds in the central and S Gulf of California along with seas of 3-4 ft. Elsewhere, winds are moderate or weaker over the Mexican offshore waters. Seas are 6-8 ft in NW swell in the waters west and south of Baja California with 3-6 ft elsewhere in the open Pacific as well as 1 ft in the N Gulf of California. For the forecast, high pressure over the U.S. Great Basin will force fresh NW winds over the Gulf of California tonight. Very large NW swell with a 16-18 second period are reaching the waters off of Baja California Norte this afternoon. These will produce 12-18 ft seas west of Baja California tonight through Fri. These seas will subside slightly Fri night, before being reinforced again Sat through Sun. Seas will diminish again Sun night and Mon. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Quiescent marine conditions dominate the waters with mainly gentle winds and seas of 3-5 ft. For the forecast, a weak pressure gradient will result in moderate or lighter winds into Sat night. A building ridge north of the area should support fresh to strong NE gap winds over the Gulf of Papagayo region Sun into early next week. Gale-force gap winds in the Gulf of Tehuantepec will cause large NW swell over the Guatemala-El Salvador offshore waters Sat night into Mon night. ...REMAINDER OF THE AREA... See Special Features Section above for details on gales that will develop tomorrow over the far NW waters and subsequent very large NW swell. A trough currently extends from 30N130W to 23N140W. A strong cold front is approaching our NW corner from the northwest. Fresh to strong SW winds are between the trough and the cold front. Seas of 12 ft or more are occurring north of a line from 30N123W to 15N140W due to a long period NW swell, with peak seas reaching around 20 ft. The weak pressure gradient between a 1022 mb high at 27N123W and the ITCZ is forcing only moderate NE trades from 08N-29N west of 110W. Seas are 8-12 ft across the remainder of the waters west of 110W due primarily to NW swell. Elsewhere across the Pacific, winds are gentle and seas are 4-7 ft. For the forecast, see the Special Features section above for details on the cold front, that will cause gale conditions over the NW corner of our waters and very large swell over much of our forecast waters. Elsewhere, weak high pressure will dominate leading to generally moderate to fresh trades through early next week. Even as the very large NW swell diminishes on Sun, seas of 8 ft or greater will reach southward to the equator and eastward to 100W on Sun through Mon. $$ Landsea