000 AXPZ20 KNHC 170938 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 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 0600 UTC surface analysis and satellite imagery through 0915 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 has its axis along 86W north of 02N to inland western Nicaragua and central Honduras. It is moving westward at 10-15 kt. This wave is within a very moist and unstable environment. Scattered moderate convection is within 120 nm east of the axis from 07N to 09N. A tropical wave has its axis along 98W/99W from 02N to 17N, moving westward at 10-15 kt. Isolated showers and thunderstorms are noted within 180 nm west of the axis from 07N to 11N. A tropical wave has its axis extending from 02N115W to 16N114W. It is moving westward near 15 kt. This wave is surrounded by a moist and unstable environment. Scattered showers and isolated thunderstorms are seen within 60 nm east of the axis from 08N to 11N and within 60 nm west of the axis from 10N to 15N. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from the far south-central Caribbean Sea near 12N73W westward to across central Costa Rica and to 10N85W to 11N96W to 11N110W to 09N120W to 14N130W and to beyond 12N140W. Aside from the convection associated with the tropical waves discussed in the section above, scattered moderate to isolated strong convection is within 60 nm south of the trough between 113W-115W. Scattered moderate convection is within 120 nm south of the trough between 99W-101W. 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. The gradient associated with a high pressure ridge over these waters is allowing for mainly gentle to moderate northwest winds north of 20N, with seas in the range of 4-6 ft due to a mix of northwest and southwest swell. Light breezes persist south of 20N outside of the Gulf of Tehuantepec, with 3 to 5 ft seas in a southwest swell. Winds over the far northern Gulf of California have diminished, but are expected to become southwest at fresh to strong speeds tonight ahead of a trough that will approach far northern Baja California. These winds will diminish to mainly fresh speeds early on Mon and continue through late Mon night. Winds there then become north at fresh speeds early Tue, with passage of the trough. This trough will precede a dissipating cold front. 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. Overnight altimeter satellite data showed seas just below 8 ft due to a northwest swell north of 29N between 125W and 130W. An area of 8 ft in a northwest swell is evident from 07N to 09N between 106W- 110W. These seas will subside to less than 8 ft by early Sun evening. Elsewhere, 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. $$ Aguirre