000 AXPZ20 KNHC 201459 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1327 UTC Thu Dec 20 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: A cold front moving across the Gulf of Mexico will reach the Bay of Campeche today. The pressure gradient between high pressure building behind the front along the Sierra Madre Oriental and the equatorial trough will generate a tight pressure gradient over the area and usher in the next gale force gap wind event. Winds will rapidly increase to gale force by late today and to strong gale force by Fri morning. The plume of strong gap winds will reach about 500 nm to the SW of the Gulf of Tehuantepec by late Fri, with seas building as high as 19 ft within the area of strong winds. The gales will persist through Fri night, then diminish on Sat as the high pressure N of the area shifts east. Fresh to strong gap winds will then persist across the Gulf of Tehuantepec through Sun. Another possible gale is forecast for the Gulf of Tehuantepec starting Sun night. Gulf of Papagayo Gale Warning: High pressure will continue to build eastward in the wake of the cold front in the Gulf of Mexico as the cold front enters the western Caribbean. This will tighten pressure gradient over the area, which will support strong gap winds across the Gulf of Papagayo by late Fri. Winds are expected to further increase, reaching gale force Fri night. Winds will diminish below gale force Sat. Seas may reach up to 13 ft within 90 to 120 nm downstream of the Gulf by early Sat. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 05N77W to 05N100W. The ITCZ extends from 05N100W to 07N140W. Scattered moderate isolated strong convection is noted from 03N to 08N E of 80W. Scattered moderate convection is noted from 05N to 09N W of 129W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see above for more on the upcoming gale force gap wind event over the Gulf of Tehuantepec. Subsiding long period NW swell will continue to propagate across the region. Seas of 8 ft or greater covers much of the open offshore waters of the discussion area. Seas in the 10 to 12 ft range will prevail off the coast of Baja California Norte through today. Seas will continue to subside and fall below 8 ft through early Sat. The next round of large swell will reach the Baja offshore waters by late Mon. Elsewhere, high pressure over the Great Basin is supporting fresh to strong NW winds mainly across the central Gulf of California. These winds will diminish through today as the area of high pressure weakens. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Please see above for more on the upcoming gale force gap wind event over the Gulf of Papagayo. Fresh to locally strong N winds are expected over the Gulf of Panama Sat night through early on Mon. Winds could become strong Sat night and Sun as seas peak around 8 ft. Elsewhere, gentle to moderate winds will persist, with seas in the 4 to 7 ft range. REMAINDER OF THE AREA... A cold front extends from 30N136W to 27N140W. The front has ushered in a fresh set of NW swell into the forecast waters, with seas reaching 13 ft W of the front. The front will gradually become diffuse through Fri. High pressure building behind the front will support an area of fresh strong winds over the tradewind belt N of the ITCZ, and W of 135W starting tonight. NW swell continues to prevail across the discussion area. Seas of 8 ft or greater are noted W of 96W. Seas will subside N of 20N and W of 120W tonight through Sat. An area of confused seas will develop south of 15N between 100W and 110W by late Sat as lingering NW swell mixes with shorter period swell from the Tehuantepec and Papagayo gap events. $$ AL