000 AXPZ20 KNHC 091552 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Wed Dec 9 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: The pressure gradient between high pressure over the Gulf of Mexico and the eastern north Pacific monsoon trough continues to support minimal gale force northerly winds across the Gulf of Tehuantepec, with peak seas to 13 ft. Winds are forecast to diminish below gale force late tonight. Swell generated from these gales will spread well away from the Tehuantepec region, with seas 8 ft or greater reaching as far west as 110W today in a mix of NE swell from the gap winds and longer period NW swell. Please read the latest NWS High Seas Forecast issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFEP2.html for more details. Of note: Based on the last 20 years, 329 gale and 106 storm- force gap wind events have been observed in the Tehuantepec region, an average of 16 gale and 5 storm events per cold season. The average starting date for Tehuantepec gale events is around October 25th, and the average date of the last event is around April 9th. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N78W to 09N105W to 1012 mb low pressure near 08N113W. The ITCZ continues from 08N113W to beyond 08N140W. Scattered moderate convection is noted from 03N to 06N east of 79W, and from 05N to 08N between 97W and 102W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for more on the Gulf of Tehuantepec gale force gap wind. A deep layer low pressure area is centered off Baja California Norte, supporting a 1013 mb surface low near Guadalupe Island. Upper dynamics on the southeast side of the upper low are supporting a small cluster of showers and thunderstorms west of Los Cabos and north of Clarion Island. Recent altimeter satellite passes indicate seas are up to 14 ft off Baja California, in primarily NW swell. The surface low is expected to drift E and weaken through early Thu. As the low moves across the waters of Baja Norte expect gentle to moderate W to SW winds before the low moves inland late tonight and weakens to a trough early Thu. High pressure will build across the Baja offshore waters Thu and Thu night to bring a return to moderate northerly winds off Baja California Thu night through Sat. Seas greater than 8 ft will prevail through the week, then subside below 8 ft Sat, just as a new round NW swell with wave heights in excess of 8 ft reaches the waters of Baja California Norte. These seas will push southward but subside to below 8 ft through early next week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to strong offshore gap winds will prevail through early Fri as high pressure prevails over the western Caribbean. Winds may reach near gale-force through tonight. Seas will build to near 10-11 ft on Thu, with seas greater than 8 ft extending well downwind of the Papagayo region by the end of the week. Elsewhwere, gentle to moderate S to SW winds will prevail south of the monsoon trough through the next several days. Swell generated in the Tehuantepec region will continue to propagate over the waters off Guatemala and El Salvador, producing seas of up to 9 ft today. Seas in the 4-6 ft range will prevail elsewhere. REMAINDER OF THE AREA... The pressure gradient between high pressure north of the area and lower pressure in the vicinity of the ITCZ, and within the monsoon trough, is supporting an area of moderate to fresh trade winds roughly from 08N to 20N west of 125W. Deep layered low pressure is supporting a 1013 mb surface low centered near 29N120W. The pressure gradient between the area of high pressure and this low is supporting moderate to fresh winds west of the low. The low will drift E and gradually weaken through early Thu. Long period NW swell is propagating over the NW portion of the forecast region, and will continue to spread SE across the forecast waters. Seas 8 ft or greater cover the waters NW of 21N110W to 02N140W. Seas greater than 12 ft cover much of the waters north of 20N. Seas greater than 8 ft with this swell will cover much of the waters west of 105W by tonight. Seas will slowly subside, and fall below 8 ft over much of this area by Sat. $$ Christensen