000 AXPZ20 KNHC 181537 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Mon Oct 18 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 1500 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Winds to gale force continue through the Gulf of Tehuantepec this morning. This is a result of cooler, drier air funneling across the Tehuantepec isthmus following an early season cold front that moved through the southwest Gulf of Mexico yesterday. While the airmass is modifying, high pressure building behind the front is still supporting winds to gale force. A recent radar altimeter satellite pass showed seas in excess of 10 ft just east of the main plume of gale force winds. So peak seas to at least 11 ft are plausible. The gales will diminish this afternoon as the high pressure weakens and shifts eastward. Seas will subside below 8 ft by late tonight. Please see the latest High Seas Forecast at http://nhc.noaa.gov/text/MIAHSFEP2.shtml for more details. ...TROPICAL WAVES... A tropical wave is along 80W north of 02N through central Panama, moving west at 10 to 15 kt. Scattered moderate convection is active north of 03N and west of 82W. A tropical wave extends along 91W/92W north of 02N to Guatemala, moving westward at 10-15 kt. Scattered moderate convection is from 06N to 10N between 88W and 90W. A tropical wave extends along 105W from 02N to 15N, moving westward at 10-15 kt. No significant convection is noted with this wave. A tropical wave extends along 122W/123W from 01N to 15N, moving westward at 15 kt. Scattered moderate to isolated strong convection is from 08N to 11N between 118W and 130W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 07N78W to 11N100W to 1010 mb low pressure near 11N112W, to 10N125W to 13N135W to beyond 11N140W. Aside from the convection associated with the tropical waves discussed in the section above, scattered moderate convection is observed from 07N to 12N between 95W and 100W, and from 08N to 10N between 107W an 114W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See the Special Features section above for more information on the ongoing Gale Warning for the Gulf of Tehuantepec. A weak pressure gradient across the region is maintaining gentle to locally moderate NW winds over the Baja California peninsula offshore waters and light to gentle variable winds across the southern half of the Gulf of California and the SW Mexico offshore waters outside of the Tehuantepec area. Seas are 3 to 5 ft in mixed NW and SW swell. Over the northern Gulf of California, a surface trough is supporting fresh to locally strong SW to W winds with seas to 3 ft. Otherwise, showers and tstms are across the offshore waters of Oaxaca and Chiapas associated with the frontal boundary N of the area and a tropical wave approaching from the E. For the forecast, gentle to moderate winds will dominate elsewhere into mid week with mixed NW and SW swell subsiding on Tue. By Tue night, new NW long period swell will start to move into the waters off Baja California Norte. The swell will continue south and bring seas in excess of 8 ft to the offshore waters of Baja California by late Fri. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Earlier scatterometer data continued to show light to gentle variable winds north of the monsoon trough and gentle to moderate SW winds south of it. Seas across the region are in the 4-5 ft range in SW swell. Otherwise, scattered showers and isolated thunderstorms prevails in the offshore waters of Costa Rica, Nicaragua and Guatemala due to the passage of a tropical wave. For the forecast, a broad area of low pressure is expected to form in a few days a couple of hundred miles S of the coast of southern Mexico. Some slow development of this system is possible thereafter as it moves WNW off the coast of Mexico. REMAINDER OF THE AREA... Moderate to locally fresh NE winds continue over the waters N of the monsoon trough and west of 120W, with gentle to moderate winds south of the monsoon trough. Gentle to moderate N to NE winds and seas in the 5-7 ft range will change little into Tue. A NW swell expected to raise seas to 8 ft will move into the waters N of 27N between 120W-130W Tue into Wed, then subside. Looking ahead, another round of NW swell will accompany a cold front that will move into the waters N of 28N and W of 130W Tue night, with seas in excess of 8 ft dominating the waters NW of a line from Guadalupe Island to 14N140W by late Thu. Reinforcing NW swell will follow over the same area through late Fri. $$ Christensen