000 AXPZ20 KNHC 192206 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Thu Nov 19 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 1800 UTC surface analysis and satellite imagery through 2130 UTC. ...SPECIAL FEATURES... Tropical Storm Polo has been downgraded to a Post-Tropical Cyclone. Polo is centered near 16.9N 121.3W at 19/2100 UTC 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 convection is within 90 nm north semicircle of the center. 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 late Friday. 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 is supporting gale force northerly winds across the Tehuantepec region. This long-lived gale event is expected to last through Sun evening. Wave heights will build to a maximum of about 21 ft downstream of the Gulf of Tehuantepec through this evening. The leading edge of 8 ft or greater sea from associated swell 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 southern Costa Rica to the remnant low of tropical cyclone Iota near 10N93W, then to 09N100W to 09N110W to 14N118W to 10N130W. The ITCZ begins near 10N130W and continues beyond the area at 08N140W. Scattered moderate is from 10N to 14N between 100W and 106W. 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 across the offshore forecast waters west of Baja California, producing gentle to moderate northwesterly winds. Wave heights are 5-7 ft in long-period northwest swell. Little change in winds and sea heights is expected through Mon. A weakening stationary front extends from 30N117W to 23N137W. The front will gradually dissipate through Fri as it moves across northern Baja California and the northern Gulf of California. As this happens, strong high pressure will build south-southeastward over the offshore waters through the weekend. 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 wave heights generated in the Tehuantepec region will propagate into the offshore waters of Guatemala and El Salvador through early Fri before subsiding. REMAINDER OF THE AREA... See the Special Features section above for details on Post-Tropical Cyclone Polo. A weakening stationary front extends from 30N117W to 23N137W. The front will gradually dissipate through Fri as it moves across northern Baja California and the northern Gulf of California. A set of long-period northwest swell behind the front will shift eastward through Fri and gradually decay. A weak 1012 mb low pressure currently NW of the area has an attendant cold front that extends to the southwest well to the west of the discussion area. The low will further 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 8-9 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 over a good portion of the western half of the area as the gradient associated to the aforementioned strong high pressure tightens. Wave heights with these winds are expected to reach the range of 8-10 ft as an existing northwest swell component, as mentioned earlier, helps to boost wave growth there. $$ Ramos