000 AXPZ20 KNHC 261511 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1511 UTC Wed Oct 26 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Hurricane Seymour centered near 16.9N 120.2W at 1500 UTC or about 682 nm west-southwest of the southern tip of the Baja California peninsula, moving west-northwest at 13 kt. Estimated minimum central pressure is 949 mb. Maximum sustained winds are 120 kt with gusts to 150 kt. Numerous moderate and scattered strong convection is within 75 nm in the northeast semicircle, and within 45 nm in the southwest semicircle. Scattered moderate and isolated strong convection is elsewhere within 180 nm in the northeast semicircle, and within 75 nm in the southwest semicircle. Seymour is forecast to turn to the northwest later today, then to the north-northwest and eventually north, with a decrease in forward speed Thursday through Friday. Seymour is forecast to weaken through the day today, with rapid weakening occurring by tonight or Thursday. 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 next several days. As a result, northerly winds will continue to pulse to minimal gale force during the next several days, with the strongest winds likely during the overnight into the early morning hours. Winds are forecast to peak to up to 40 kt late tonight into early Thursday as the pressure gradient tightens even more. Seas will build to up to 12 ft during the gale force winds, except up to 14 ft late tonight into early Thursday. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N83W to 10.5N91W to low pressure near 09N107W to 14N112W, then resumes from low pressure near 16N128W to low pressure near 13N133W to 11N140W. Scattered moderate convection is within 60 nm south of Central America east of 86W, from 06N to 08N between 96W and 99W, and also within 150 nm southeast of the monsoon trough axis between 126W and 133W. Scattered moderate and isolated strong convection is also within 120 nm in the southeast quadrant of the low near 09N107W, with scattered moderate convection from 07N to 11N between 108W and 111W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See the special features section for details on the persistent Gulf of Tehuantepec gap wind event. High pressure at 1020 mb is centered west of Baja California Norte near 30N120W with a ridge axis extending southeast of the high to near 14N108W. This high will continue to support gentle to moderate anticyclonic flow across the waters offshore of the Baja California peninsula, diminishing to gentle throughout this weekend, as the pressure gradient weakens due to an approaching and decaying cold front. Combined seas of 4 to 7 ft, except up to 8 ft in the southwest portion of zone PMZ015 related to Hurricane Seymour, will subside to 4 to 6 ft throughout late this week into the weekend, then will build to 6 to 9 ft by Sunday as a new set of northwest swell arrives. 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... Offshore of the Gulf of Papagayo, fresh northeast to east winds will diminish during the remainder of the morning hours. Elsewhere gentle to moderate south to southwest winds are found south of the monsoon trough, while mainly gentle west to northwest winds prevail to the 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 30N132.5W to 24N140W. Fresh to strong south to southwest winds are occurring within 60 nm of the front, north of 26N. These winds are forecast to diminish to 20 kt or less tonight. Associated northwest swells of 8 to 11 ft is sweeping across the northwest part of the discussion area mainly behind the front. The front will move east-southeastward through early Thursday, temporarily stalling as 1009 mb low pressure develops along it near 29N129W. The low will move northeast of the area by Thursday night pulling the trailing cold front to the east. The front will continue to weaken as it approaches Baja California Norte late this weekend. The northwest swell will continue to propagate southeast, and eventually mix with seas generated by Seymour, resulting in a sizable area of confused seas. Otherwise, weak northeast to southwest ridging ahead of the cold front will gradually dissipate through Wednesday. Mainly moderate to locally fresh trades will prevail outside of the influences of the cold front and Seymour, with combined seas of 4 to 7 ft. A new cold front will move into the northwest corner this weekend, bringing with it a reinforcing set of northwest swell. $$ LEWITSKY