000 AXPZ20 KNHC 181603 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Wed Nov 18 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 1200 UTC surface analysis and satellite imagery through 1545 UTC. ...SPECIAL FEATURES... Recently upgraded Tropical Storm Polo is centered near 16.3N 116.0W at 18/1500 UTC or 535 nm southwest of the southern tip of Baja California moving WNW at 10 kt. The estimated minimum central pressure is 1004 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Satellite imagery shows that banding features have become better defined during the overnight and morning hours. A small central dense overcast (CDO) is noted as well. The satellite shows scattered moderate to isolated strong within 90 nm of the center in the NE quadrant and within 60 nm of the center in the SE quadrant. Polo is forecast to maintain is present motion through today, then turn toward the west by Thu. Little change in strength is expected today, with gradual weakening anticipated to begin on Thu. Polo is forecast to weaken to a depression late on Thu and degenerate into a remnant low pressure area on Fri. Please read the latest High Seas Forecast issued by the National Hurricane Center at website- https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and the latest Tropical Depression Twenty-One-E NHC Forecast/ Advisory and Public Advisory at www.hurricanes.gov for more details. Gulf of Tehuantepec Gale Warning: The pressure difference between strong high pressure over southern Mexico and low pressure south of Mexico is supporting strong gale force north winds across the Tehuantepec region. This event will be long- lived, with gale force winds forecast to reach near storm force this morning this evening and into early Thu. Wave heights could build to 14-20 ft each night, and up to 21 ft downstream of the Gulf of Tehuantepec tonight and early Thu morning. 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 the remnant low of tropical cyclone Iota that is centered near 14N90W with a pressure of 1006 mb, southwestward to 09N96W to and westward to 09N106W. It resumes at 13N116W to 10N126W to 09N132W, where overnight scatterometer data indicates that it transitions to the ITCZ to beyond the area at 08N140W. Scattered moderate convection is seen within 60 nm south of the trough between 116W-120W. 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. The gradient associated to a ridge that 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. This swell will decay slightly today, but wave heights will be in the same range of 5-7 ft beginning Thu afternoon. A weakening cold front that extends from southern California and well to the west of Baja California will quickly dissipate as it reaches the waters just west of Baja California Norte on Thu. In the wake of the front, strong high pressure will build eastward over the water west of Baja California, with the associated gradient expected to bring fresh to strong northwest across the northern Gulf Sat night and Sun. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Moderate to fresh southwest winds are present south of the monsoon trough east of 100W, with mainly gentle west to northwest winds north of the trough. Sea heights are generally 5-7 ft. Large seas generated in the Tehuantepec region will propagate into the offshore waters of Guatemala and El Salvador through Thu. REMAINDER OF THE AREA... See the Special Features section above for details on recently upgraded Tropical Storm Polo. A weakening cold front that is over the northwest and north- central waters along a position from 32N123W to 26N130W to 22N140W. This front will quickly dissipate as it reaches the northeast waters on Thu. This front will quickly dissipate as it reaches the northeast waters on Thu. An area of long-period northwest swell behind the front will shift eastward through Fri while gradually decaying. A low pressure system is expected to stall near 31N140W Thu and Fri, then shift westward on Sat as a strong ridge builds north of 30N. Tropical Storm Polo will weaken to depression late on Thu and degenerate into a remnant low pressure area on Fri. Associated seas greater than 8 ft will persist north of the remnant low of Polo due to a persistent gradient between the low and a strengthening ridge to the north. $$ Aguirre