000 AXPZ20 KNHC 202149 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2013 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 1800 UTC surface analysis and satellite imagery through 2045 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A cold front moving across the Gulf of Mexico has already introduced a strong ridge of high pressure along the Sierra Madre Oriental. A tight pressure gradient over the area between and usher in the next gale force gap wind event. Winds will abruptly increase to gale force as the event begins this evening, then 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 moving from the Gulf of Mexico into the NW Caribbean. This will tighten the pressure gradient over the area and 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. Strong gap winds will continue to flow over the Gulf of Papagayo through Tue night, but the areal coverage of the winds will gradually decrease. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 09N75W to 04N84W to 03N92W to 03N100W. The ITCZ continues from 03N100W to 05N109W to 05N131W to beyond 07N140W. Scattered moderate isolated strong convection is noted from 04N to 07N E of 88W and from 11N to 13N between 116W and 123W. Scattered moderate convection is found from 05.5N to 10.5N W of 129W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see above for more on the gale force gap wind event about to begin over the Gulf of Tehuantepec. Subsiding long period NW swell will continue to propagate across the region. Seas of 8 ft or greater cover much of the open offshore waters of the discussion area. Seas in the 10 to 12 ft range will linger off the coast of Baja California Norte this evening but have begun to subside. Seas everywhere outside the Gulf of Tehunatepec 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 this evening 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. Strong N winds are expected over the Gulf of Panama Fri night through Sun night. Seas will peak around 8 ft Sun morning. 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 30N135W to 26.5N140W. The front has already introduced a fresh set of NW swell into the forecast waters, but seas in the vicinity of the front have subsided to between 11 and 12 ft as the swell have begun to decay. The front will gradually become diffuse through Fri. High pressure building behind the front will support an area of fresh to strong winds over the trade wind belt N of the ITCZ, W of 135W starting tonight. NW swell continues to prevail across the discussion area. Seas of 8 ft or greater are noted W of 93W. The swell are decaying and 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. $$ CAM