000 AXPZ20 KNHC 200339 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Fri Nov 20 2020 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 0240 UTC. ...SPECIAL FEATURES... The remnant low of Post-Tropical Cyclone Polo is centered near 17N 121.5W moving W at 10 kt. The estimated minimum central pressure is 1007 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. Scattered moderate isolated strong convection has flared up over the remnants within 120 nm NE and 45 nm SW semicircle of the center. Seas of 8 to 11 ft are found to the N and NW of the low. Polo is expected to continue to move towards the west through late Friday. Gradual weakening is expected, and the remnant low is forecast to dissipate by Friday night. For the final advisory on Polo please read the latest NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. Gulf of Tehuantepec Gale Warning: The gradient between strong high pressure over southern Mexico and low pressure in the Pacific continues to support gale force northerly winds across the Tehuantepec region. This long-lived gale event is expected to last through Sun evening. Wave heights are estimated to be 15-18 ft downstream of the Gulf of Tehuantepec. The leading edge of 8 ft or greater sea from the associated swell being generated is forecast to reach as far west as 110W by late Fri. Please read the latest NWS High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N75W to 07N81W to 09N106W to 12N120W. The ITCZ begins near 12N120W and continues beyond the area at 09N140W. Scattered moderate convection is noted N of 06N E of 81W. Scattered moderate isolated strong convection is noted from 10.5N to 13.5N between 100W and 107W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A Gale Warning remains in effect for the Gulf of Tehuantepec. Please see the Special Features section above for details. A ridge extends southward across the offshore forecast waters west of Baja California, extending from a 1030 mb high just off the northern California coast. The associated pressure gradient is producing moderate northernly winds across the waters from Punta Eugenia northward, and gentle to moderate northwesterly winds to the south. Wave heights are 5-7 ft in long-period northwest swell. Little change in winds and seas are expected through Mon. Moderate northerly winds prevail across central portions of the Gulf of California, where seas are 3-5 ft. These conditions will prevail through Fri morning and then improve modestly through Sun. An old frontal boundary across the waters offshore of southern California has become diffuse this evening. The remnants will move southward across northern Baja California and the northern Gulf of California tonight and Fri. As this happens, strong high pressure will build south-southeastward over the offshore waters through the weekend and strengthen the wind flow slightly OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Moderate southwest winds are south of the monsoon trough east of 100W, with gentle west to northwest winds north of the trough. Wave heights are generally 5-7 ft, except 7-9 ft in mixed swell between 88W and 100W. Large waves generated across the Tehuantepec region will propagate into the offshore waters of Guatemala and El Salvador through Fri before subsiding. REMAINDER OF THE AREA... See the Special Features section above for details on Post-Tropical Cyclone Polo. A small 1013 mb low pressure currently just NW of the area has an attendant cold front that extends to the southwest across about 30N140W and then continues well to the west of the discussion area. The low will weaken as it moves to near 33N137W by early Fri, with the cold front just moving into the far northwest part of the area. The front will then become stationary and weaken into Fri, before degenerating to a trough later on Fri. This low pressure system and front will usher in large northwest swell into the northwest part of the area on Fri, with wave heights of 8-10 ft and up to 10 or 11 ft just north of that part of the area. Strong high pressure will build south- southeastward across the area through the weekend. This will act to nudge the trough westward on Sat. The pressure gradient between the high pressure and the remnant low of Polo should allow for wave heights in the range of 7-10 ft to exist west of about 125W and from 14N to 22N through Sat. By late Sat night into Sun, a rather large area of fresh to strong trades is forecast by the global models to develop west of 120W as the pressure gradient associated with the aforementioned strong high pressure tightens. Wave heights with these winds are expected to reach the range of 8-10 ft. $$ Stripling