000 AXPZ20 KNHC 300300 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 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 0000 UTC surface analysis and satellite imagery through 0300 UTC. ...SPECIAL FEATURES... Tropical Storm Marie is centered near 13.8N 110.4W at 30/0300 UTC moving W at 11 kt. Estimated minimum central pressure is 1003 mb. Maximum sustained wind speed is 40 kt with gusts to 50 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 09N to 17N between 108W and 118W. 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 Wed night. 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 strong gale force gap wind event across the Gulf of Tehuantepec. Winds will rapidly increase to gale force before sunset today, reaching 40 kt tonight. At that time, seas will build to 15-18 ft. Gale force winds will continue through Fri night. Swell generated from this event is forecast to reach 100W on Wed. 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 13N100W, then resumes W of T.S. Marie near 13N115W to 09N140W. Scattered moderate convection is noted from 05N to 11N between 86W and 95W. Scattered moderate isolated strong convection is noted from 07N to 13N between 100W and 105W. Scattered moderate convection is noted from 08N to 11N between 129W and 140W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see above for more on the Gulf of Tehuantepec gale force gap wind event. Elsewhere, a weak ridge west of Baja California will maintain gentle to moderate NW to N winds across the region for the next few days. Gentle to moderate northerly winds will prevail across the northern Gulf of California through tonight while mainly light to gentle winds are expected elsewhere across the Gulf most of the forecast period. 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 Wed night 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. Long period SW swell is moving through the waters between Ecuador and the Galapagos Islands, where seas are 8-9 ft. These seas will subside below 8 ft on Wed. Seas generated by the gap wind event in the Tehuantepec region will propagate across the offshore waters of Guatemala and El Salvador beginning on Wed morning. 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 Wed night. 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