000 AXPZ20 KNHC 180355 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Thu Jan 18 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 0000 UTC surface analysis and satellite imagery through 0245 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Strong high pressure continues to build southward across eastern Mexico and the western Gulf of Mexico behind yet another cold front, and is supporting a tight pressure gradient across southern Mexico. Gale force winds of 40 to 45 kt prevail across and downwind of Tehuantepec and are expected to through the early morning hours of Thu. Winds are then expected to gradually diminish below gale force by Friday afternoon. The resultant plume of northerly swell will continue to propagate well southward of the Gulf of Tehuantepec waters, mixing with long period NW swell to produce seas in excess of 8 ft to near 650 nm due S of Tehuantepec and over 800 nm SW of the there. Maximum seas tonight will remain around 19 ft near the strongest winds, and gradually subside by the end of the week as the winds diminish. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough axis extends from 07N77W TO 09N86W TO 05N93W. The ITCZ extends from 05N93W TO 07N130W to beyond 09.5N140W. Scattered moderate isolated strong convection is occurring from 03N to 10N between 77W and 91W. Scattered moderate isolated strong convection is within 75 nm S and 120 nm N of the axis between 95W and 110W. Scattered to locally numerous moderate to strong convection is occurring within 90 nm S and 360 nm N of ITCZ between 110W and 137W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the special features section for information about the ongoing gale warning in the offshore waters of the Gulf of Tehuantepec. In the Gulf of California, light to moderate NW flow is expected across across the entire gulf waters through Friday afternoon. Winds will become southerly Friday evening ahead of an approaching cold front, increasing to fresh to strong in the northern gulf Friday night, then shifting to NW to N behind the front. The front will gradually become ill defined as it moves southward across the gulf during the day Saturday with mainly moderate to fresh northerly flow in its wake for the end of the weekend, except increasing to fresh to strong in the central and southern Gulf Sunday afternoon and night as the pressure gradient tightens across that area. Elsewhere across the offshore waters of Mexico, large NW swell continues to propagate SE across the waters, with seas of 8-11 ft prevailing, except 5-8 ft between 98W and 105W. The large swell is generating high and powerful surf along the coasts and outer reefs of the Baja California peninsula and mainland Mexico which will continue this evening, with coastal flooding possible. Another pulse of NW swell will reach the offshore waters off Baja California Norte Thursday night. Seas will peak near 13-15 ft by Friday, while seas of 12 ft or greater will spread across the offshore waters off the entire length of the Baja Peninsula through the upcoming weekend. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh NE gap winds winds will pulse to strong each night and early morning across the Gulf of Papagayo through Saturday morning, diminishing thereafter. Winds will also pulse to fresh to strong offshore of other Central America gulfs and gap wind areas tonight into early Thursday. Elsewhere, mainly light to gentle offshore winds will prevail N of 09N, with light to gentle southerly flow S of 09N. NW swell originating from the gale wind event in the Gulf of Tehuantepec along with longer period NW swell will arrive across the area waters Thursday and Friday, building seas offshore to 5-7 ft. REMAINDER OF THE AREA... Large, long period NW swell continues to propagate SE across the forecast waters, with seas of 8 to 12 ft across the waters W of 95W-100W. A weakening cold front has moved into the far NW portion of the area from 30N137W TO 28N140W, and will continue SE through early Thursday, and be reinforced by building high pressure Thursday evening. Winds W of the reinforced front will increase to fresh to strong Thursday evening, with fresh to strong trades gradually spreading across the waters N of 10N W of 110W during the upcoming weekend as the front dissipates across the N central waters. $$ Stripling