000 AXPZ20 KNHC 171602 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Sun Oct 17 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: High pressure is building across the Gulf of Mexico as a cold front pushes across the basin. The associated tight gradient has initiated gale force gap winds over the Gulf of Tehuantepec. These winds will continue through early Mon. Seas are expected to build to 9-13 ft downwind of the gale force winds by early Sun evening, then slowly subside Mon. 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 87W north of 01N to inland into central Honduras, moving westward at 10-15 kt. This wave is within a very moist and unstable environment. Scattered moderate convection is within from 09N to 13N between 87W and 91W. A tropical wave is along 99W/100W from 02N to 17N, moving westward at 10-15 kt. Scattered moderate to isolated strong convection is noted 11N to 14N between 95W and 100W. A tropical wave is along 115W/116W from 01N to 16N, moving westward near 15 kt. Scattered moderate convection is evident from 07N to 10N between 116W and 118W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 08N78W to 10N115W to 13N125W to beyond 13N140W. Aside from the convection associated with the tropical waves discussed in the section above, scattered moderate convection is noted within 60 nm either side of the monsoon trough between 100W and 127W, and within 120 nm south of the monsoon trough west of 133W. 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. Relatively weak high pressure is maintaining only gentle to moderate mostly NW winds over Mexican offshore waters outside of the Tehuantepec area. Seas are 4 to 6 ft in open waters largely due to SW swell. In addition to the showers and thunderstorms off western Oaxaca associated with the tropical wave along 99W/100W, a few showers were active off Cabo Corrientes, but are diminishing. For the forecast, gentle to moderate winds will persist elsewhere into mid-week. Looking ahead, seas will build off Baja California north of Cabo San Lazaro beginning Tue night as a northwest swell moves through the northern offshore waters. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Light to gentle north winds prevail north of the monsoon trough, while gentle to moderate southwest winds are to its south. Scattered showers and isolated thunderstorms are noted in the Gulf of Panama and offshore the border between Costa Rica and Panama. Seas over these waters are in the 4-6 ft range. For the forecast, seas off western Guatemala beyond 120 nm may peak to 8 ft into Mon in a mix of north swell from the Tehuantepec region and longer-period southwest swell. Elsewhere seas will average about 4-6 ft due to a southwest swell. Fresh to northeast to east winds are expected in the Gulf of Papagayo Mon night and Tue. Scattered showers and isolated thunderstorms are expected to continue across the region through early next week. REMAINDER OF THE AREA... Moderate to locally fresh northeast winds continue over the waters north of the monsoon trough and west of 120W, with gentle to moderate winds south of the monsoon trough. Earlier altimeter data showed seas to 8 ft from 05N to 10N between 110W and 115W, and north of 29N between 125W and 130W. Recent altimeter data along with model output hint seas have already subsided below 8 ft in these areas. Gentle to moderate north to northeast winds and seas in the 5-7 ft range will change little into the early part of the upcoming week. A northwest swell expected to raise seas to 8 ft will move into the waters north of 27N between 120W- 130W Tue into Wed, then subside. Looking ahead, a more substantive area of northwest swell will accompany a cold front that will move into the waters north of 28N and west of 130W Tue night, with seas in excess of 8 ft dominating the waters northwest of a line from Guadalupe Island to 14N140W by late Thu. $$ Christensen