000 AXPZ20 KNHC 041433 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. Overnight 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. Please refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. A low pressure system 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 pressure center and a trough extending to the N by Friday night into Saturday. The low will lift north of the area Monday. Seas are forecast to build to 12-16 ft within the area of gale force winds. ...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. Seas in the range of 3-5 ft will continue over most of the offshore waters, while seas in the 1-3 ft range will prevail in the Gulf of California. NW swell will propagate into the region, with seas building in the range of 5-7 ft through the waters offshore Baja California Norte tonight. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... NE winds will pulse to near gale force during the overnight 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... NW swell is propagating across the NW waters. Seas of 8 ft or greater are covering the waters west of a line from 30N123W 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 the end of the week. Low pressure 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 near gale force winds west of the low pressure center Friday night. There is the possibility for winds to increase to gale force west of the low by Saturday. The low will lift north of the area Monday. A cold front is expected to move into into the NW waters next Monday, with increasing winds and building seas. $$ GR