000 AXPZ20 KNHC 272135 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Wed Dec 27 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... Gale Warning Far NW Waters and Very Large Swell Event: A cold front will move southeastward across the NW waters tomorrow and reach from 30N128W to 22N140W by Fri morning. SW gales are expected ahead of the front north of 28N west of 135W on Thu as well as W to NW gales behind the front north of 28N west of 135W on Thu night. A morning 1430 UTC altimeter pass showed seas already reaching around 27 ft at 30N138W along our N border. 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 on Thu before momentarily diminishing on Fri. A second reinforcing NW swell will arrive Thu night producing a peak of 30 ft seas along our NW corner waters Thu night. This will force seas of 12 ft or greater over most of our waters north of 07N west of 115W through Sat night before gradually diminishing early next week. 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 coast of Costa Rica near 10N86W to 05N98W. The ITCZ extends from 05N98W to beyond 06N140W. Scattered moderate and isolated convection is occurring from 03N-07N west of 128W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A 1024 mb high centered near 27N122W 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 fresh NW winds in the central and S Gulf of California along with seas of 3-5 ft. Elsewhere, winds are moderate or weaker over the Mexican offshore waters. Seas are 7-9 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 1-2 ft in the N Gulf of California. For the forecast, high pressure over the U.S. Great Basin is expected to force fresh NW winds over the Gulf of California tonight and again Thu night with gentle to moderate winds elsewhere. Over the Gulf of Tehuantepec, winds draining from the Chivela Pass will force fresh to locally strong N winds Thu into Fri morning. By Fri night, a strong cold front pushing across the W Gulf of Mexico will induce a N gale-force gap wind event over the Gulf of Tehuantepec. Gales should continue through Sat night before steadily subsiding on Sun. Very large NW swell with a 16-18 second period will reach the waters off of Baja California Norte tomorrow. This will produce 12-16 ft seas west of Baja California Thu through Fri, subsiding slightly on Fri night, then reinforced again on Sat and Sun, before diminishing 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 gentle to moderate winds and seas of 3-5 ft. For the forecast, a weak pressure gradient will result in moderate or lighter winds through 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. A gale-force gap wind event over the Gulf of Tehuantepec should cause large NW swell over the Guatemala-El Salvador offshore waters Sat night into early next week. ...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 cold front currently extends from 30N130W to 25N140W. Fresh SW winds are ahead of this front N of 28N and between 127W-131W. Seas of 12 ft or more are occurring north of a line from 30N129W to 23N140W due to a long period NW swell. The pressure gradient between a 1024 mb high at 27N122W to the ITCZ is forcing fresh NE trades from 07N-14N west of 127W. Seas are 8-9 ft in mixed wind waves and NW swell. Elsewhere across the Pacific, winds are moderate or lighter and seas are 5-7 ft. For the forecast, the initial cold front will move slowly southeastward and dissipate this evening. See the Special Features section above for details on the second 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 and Mon. $$ Landsea