000 AXPZ20 KNHC 300844 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Wed Sep 30 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 0600 UTC surface analysis and satellite imagery through 0840 UTC. ...SPECIAL FEATURES... Tropical Storm Marie is centered near 14.1N 112.5W at 30/0900 UTC moving W at 14 kt. Estimated minimum central pressure is 1000 mb. Maximum sustained wind speed is 50 kt with gusts to 60 kt. Numerous moderate to scattered strong convection is noted within 90 nm W and 60 nm E semicircles. Scattered moderate isolated strong convection was noted elsewhere from 07N to 19N between 110W and 120W. Marie is forecast to steadily intensify as it moves on a westward to west- northwestward track during the next several days. The current forecast has Marie reaching hurricane intensity tonight. Please read the latest NHC Public Advisory at https://www.nhc.noaa.gov/text/MIATCPEP3.shtml and Forecast/ Advisory at https://www.nhc.noaa.gov/text/MIATCMEP3.shtml for more details. Gulf of Tehuantepec gale warning: The pressure gradient between high pressure building in the wake of a cold front in the Gulf of Mexico and the eastern Pacific monsoon trough has tightened over the area. This has increased winds funneling through the Chivela Pass into the Gulf of Tehuantepec, and has started a gale force gap wind event across the Gulf of Tehuantepec. Seas will build to 15-18 ft during this event. Gale force winds will continue through early Sat. Swell generated from this event is forecast to reach 100W today. Please read the latest NWS High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFEP@.shtml for more details. Of note, the 20-year climatology of the Tehuantepec gap wind events indicates that on average 16 gale-force events and 5 storm force-events occur in the Gulf of Tehuantepec each cold season. Most gale-force events occurred during November and December, while most storm-force winds occurred in January. Based on latest model trends and the present evolving synoptic scale setup, this forecast event most likely will supersede the previously recorded earliest start date of October 3rd. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 10N85W to 13.5N101W, then resumes W of T.S. Marie near 13N118W to 10N140W. Scattered moderate isolated strong convection is noted from 06N to 15N between 96W and 106W. Scattered moderate convection is noted from 10N to 12N between 135W and 140W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see above for more on the Gulf of Tehuantepec gale force gap wind event. A weak ridge west of Baja California will maintain gentle to moderate NW to N winds across much of the region for the next few days. Elsewhere, moderate to fresh east to southeast winds are generally expected across the waters from Las Tres Marias Islands to Puerto Angel for the next few days as Marie moves away from the region. Marie is expected to become a large hurricane. The size of the system will generate a large area of seas greater than 8 ft spreading from swell out and away the cyclone center. This south swell will spread across the offshore waters west of the Baja California peninsula tonight into the weekend. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Moderate southerly flow prevails S of the monsoon trough, with gentle winds north of the monsoon trough. Combined seas are currently 6 to 8 ft in a mix of wind waves and southerly swell. These seas will subside below 8 ft today. Seas generated by the gap wind event in the Tehuantepec region will start to propagate across the offshore waters of Guatemala and El Salvador today. REMAINDER OF THE AREA... Please see Special Features section above for more information on T.S. Marie. Outside of T.S. Marie, a weak pressure gradient prevails west of 120W, with gentle to moderate winds prevailing N of the monsoon trough to 20N, and gentle to moderate winds S of the monsoon trough. The cross equatorial swell across the waters S of 15N has started to subside, however seas remain in the 7-8 ft range. These seas will continue to subside trough the middle of the week. New NW swell will propagate into the NW waters the middle of the week. Seas will build to 9 ft over the far NW waters by tonight. T.S. Marie is expected to become a large hurricane. The size of the system will generate a large area of seas greater than 8 ft spreading well away from the cyclone center. By Saturday, seas greater than 8 ft will cover much of the waters N of 10N and W of 115W. $$ AL