000 AXPZ20 KNHC 231610 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Thu Sep 23 2021 Tropical Weather Discussion for the eastern Pacific Ocean from 03.4S to 30N, east of 120W including the Gulf of California, and from the Equator to 30N, between 120W and 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 1530 UTC. ...SPECIAL FEATURES... Gale force northerly gap winds occurring across the Gulf of Tehuantepec overnight are assumed to have diminished to 20-30 kt this morning, and the gale warning has been discontinued. High pressure continues over Mexico across the eastern slopes of the Sierra Madre Mountains, in the wake of an early season cold front that has stalled across Mexico along about 19.5N and into the southwest Gulf of Mexico. Seas of 8 to 13 ft prevail across and downstream of the Tehuantepec region. Winds and seas will diminish further today, but this northerly gap wind event will continue through Sun night. Please, refer to 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. ...TROPICAL WAVES... The axis of a tropical wave is along 117W from 06N to 20N, moving west at 10 to 15 kt. Associated convection is occurring near the monsoon trough and south of 15N, is described below. A 1009 mb low pressure center is near 18.5N123W and is accompanied by very active convection this morning. Scattered to numerous moderate to strong convection is noted within 120 nm across the N semicircle, while widely scattered moderate convection of noted within 210 nm across the SW quadrant. This system is forecast to move over cool waters and into an environment of stable air and strong upper-level winds, which should inhibit further development. A tropical wave is analyzed along 135W from 10N to 18N, moving westward at 10 to 15 kt. Associated active convection is confined to along the ITCZ and is described below. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from low pressure near 11N94W 1009 mb to 09N82W to 13N92W to 08N108W to 11N116W. The ITCZ begins near 11.5N122W to 09N132W to beyond 10.5N140W. Scattered to locally numerous moderate to strong convection is from 02.5N to 07N E of 81W, and within 60 nm N and 120 nm of the ITCZ W of 122W. Scattered moderate to strong convection is from 07N to 14.5N between 83W and 117W, N of 08N between 84W and 100W, and from 05N to 12N W of 130W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Strong northerly gap winds continue across the Tehuantepec region this morning, with seas to 13 ft. This is being forced by high pressure across eastern Mexico behind an early season cold front across the Gulf of Mexico. Elsewhere, a ridge continues to extend over the offshore forecast waters of Baja California providing mainly light to gentle NW to N winds as shown by overnight scatterometer data. Locally moderate NW winds are mainly along the coast and seas across the area remain within 4 to 6 ft. Light to gentle winds are also in the Gulf of California and across the SW Mexico offshore waters. Seas are in the 3 to 5 ft range for the SW Mexico offshore waters and up to 3 ft in the Gulf of California. Gale force winds have ended across Tehuantepec are forecast to gradually diminish to moderate to fresh by Sun. See the Special Features section for further details. Surface ridging will continue to dominate the offshore forecast waters of Baja California supporting mainly gentle to moderate NW to N winds through Mon. Light to gentle winds will dominate over the SW Mexico offshore waters. Otherwise, a surface trough will move across the northern Gulf of California and will support fresh to strong southerly winds through early this evening. After that, mainly light and variable winds are expected across the entire Gulf through Mon. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Gentle to moderate southwesterly winds will continue across the offshore waters of Costa Rica, Panama, Colombia and Ecuador today, then will diminish to light to gentle through Sat. Winds will increase again to gentle to moderate Sat evening and continue through early next week. Light to gentle variable winds are forecast for the offshore waters N of 09N with pulses of moderate NE to E winds in the Gulf of Papagayo over the weekend. Cross equatorial SW swell will reach the forecast area toward the end of the week, building seas to 6-7 ft between Ecuador and the Galapagos Islands during the upcoming weekend. REMAINDER OF THE AREA... The northern open forecast waters remain under the influence of a surface ridge anchored by a 1025 mb high pressure centered near 36N140W. The pressure gradient between the ridge and low pres center near 18.5N123W supports an area of moderate to locally fresh NE winds roughly from 16N to 24N W of 120W with seas to 8 ft as indicated by recent altimeter data. Winds across this area will diminish over the weekend as the low shifts westward and weakens. $$ Stripling