000 AXPZ20 KNHC 270241 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Thu Oct 27 2016 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 0200 UTC. ...SPECIAL FEATURES... Hurricane Seymour centered near 18.7N 121.7W at 0300 UTC moving northwest at 12 kt. Estimated minimum central pressure 969 mb. Maximum sustained winds are 95 kt with gusts to 115 kt. Scattered strong convection is within 75 nm northeast and 45 nm southwest of the center. Scattered moderate isolated strong convection is elsewhere within 180 nm in the northeast semicircle, and 75 nm in the southwest semicircle. Seymour is expected to turn northward Thursday, and begin to weaken rapidly as it moves into an increasingly unfavorable environment through Friday. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP5/WTPZ25. Gulf of Tehuantepec Gale Warning...a locally tight pressure gradient will persist across southeast Mexico between high pressure located over eastern Mexico, and lower pressure south of 12N through the weekend. As a result, northerly winds will continue to pulse to minimal gale force the next several days, with the strongest winds likely during the overnight into the early morning hours. Seas will build to 12 or 13 ft during the periods of gale force winds. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 10N85W to low pressure near 09N106W 1010 mb to 12N112W, then resumes from low pressure near 15N130W 1010 mb to 10N140W. Minimal convection associated with the convergence zone. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See the special features section for details on a persistent Gulf of Tehuantepec gap wind event. High pressure centered west of Tijuana near 32N121W continues to support gentle to moderate anticyclonic flow across waters offshore of the Baja California peninsula. Winds will slowly diminish this weekend, as a dying cold front moves east and the pressure gradient weakens. 5 to 7 ft seas will subside to 4 to 5 ft by the weekend, then build to 6 to 9 ft by Sunday as another cold front and a new set of northwest swell moves eastward across the northern waters. In the Gulf of California, gentle to moderate northerly flow will prevail through Thursday, with winds becoming light and variable by early Friday as an elongated northwest to southeast trough sets up across the gulf. Seas will be 2 ft or less across the northern gulf through the weekend, and 2 to 4 ft across the southern half. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gentle to moderate south to southwest winds are found south of the monsoon trough, while mainly gentle west to northwest winds prevail north of the trough axis. Combined seas are 4 to 7 ft, primarily in long period southwest swell. Seas will decay to 3 to 5 ft this weekend. REMAINDER OF THE AREA... See the special features section for details on Hurricane Seymour. A cold front extends across the northern waters from 30N129W to 22N140W. Fresh southwest winds ahead of the front will diminish tonight. Northwest swell to 10 ft is sweeping across the northwest part of the discussion area mainly behind the front. The front will move slowly east-southeast through early Thursday, temporarily stall as a low develops along it near 29N129W, then as the low moves north of the area Thursday night it will drag the dying cold front further eastward. Northwest swell will continue to propagate southeast, and eventually mix with seas generated by Seymour, resulting in a sizable area of confused seas through Friday night. Otherwise, weak northeast to southwest ridging ahead of the cold front will gradually dissipate tonight. Moderate to fresh trades will prevail outside of the influences of the front and Seymour, with combined seas of 4 to 6 ft. A new cold front will reach the area near 30N140W this weekend, bringing a reinforcing set of northwest swell. $$ Mundell