000 AXPZ20 KNHC 041550 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1424 UTC Thu Jan 4 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: The pressure gradient between high pressure along eastern Mexico and a surface trough over the eastern north Pacific is supporting strong gale force winds over the Gulf of Tehuantepec. Latest scatterometer pass indicated winds peaking in the 40-45 kt range, with seas likely reaching near 18 ft. Gale force winds are expected to continue into the first half of the weekend, before diminishing below gale force Sunday. Swell generated from the persistent gale force winds will propagate downstream of the Gulf of Tehuantepec, with seas 8 ft or greater reaching as far S as 05N and west to 110W by Friday afternoon. Another gale force gap wind event is forecast by the computer models by Monday evening. Please refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. A low pressure system, induced by a mid to strong upper-level low, is expected to develop over the northwestern waters on Friday. The pressure gradient between this deepening low pressure area and high pressure to the west of the forecast waters will support strong to minimal gale force winds west of the low center and a trough extending to the north to near 30N129W by Friday evening. The low will lift north of the area on Monday with gale conditions persisting over the NW waters through late Saturday. Seas are forecast to build to 12-16 ft within the area of gale force winds. Please 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 08N82W to 07N94W to 06N111W. The ITCZ continues from 06N111W to beyond 09N128W to 09N140W. Scattered moderate convection is noted from 04N to 08N E of 86W to the coast of Colombia. Similar convection is from 05N to 08N between 91W and 99W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see Special Features section above for more details about the ongoing gale force wind event in the Gulf of Tehuantepec. Relatively tranquil marine conditions will persist through Friday, with light to gentle winds prevailing across the forecast waters under the influence of a 1019 mb high pressure located near 27N119W. Seas in the range of 3-5 ft will continue over most of the offshore waters through today, while seas in the 1-3 ft range will prevail in the Gulf of California, with the exception of 3-4 ft across the central waters through early Friday. NW swell will propagate into the region, with seas building in the range of 5-7 ft through the waters offshore Baja California Norte this evening. The high pressure will reach a position to near 30N121W by early Friday morning. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: NE winds will pulse to near gale force during the overnight and early morning hours starting tonight as high pressure builds north of the area tightening the pressure gradient. Light to gentle NE-E winds will prevail elsewhere to the 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 details about a developing low pressure system over the NW waters. The pressure gradient between this low and high pressure to the west of the forecast waters will also support a large area of fresh to strong northerly winds roughly N of 20N W of 130W with seas of 8-12 ft with NW swell. Fresh to strong southerly winds are also expected N of 20N E of low center to about 124W with similar sea heights. Currently, seas of 8 ft or greater are covering the waters NW of a line from 30N124W to 17N128W to 13N140W, with seas peaking near 11 ft over the far NW waters as depicted by the latest altimeter data. The swell will continue to propagate southeastward, with seas 8 ft or greater covering much of the water north of 10N and west of 125W by tonight. A cold front is expected to move into into the NW waters next Monday, with increasing winds and building seas. $$ GR