000 AXPZ20 KNHC 082208 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Tue Dec 8 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 1800 UTC surface analysis and satellite imagery through 2120 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: The pressure gradient between high pressure along the eastern slopes of the Sierra Madre in eastern Mexico and the eastern north Pacific monsoon trough continues to support gale force northerly winds across the Gulf of Tehuantepec. These gales currently extend SSW and offshore to near 14N95.5W, with peak seas to around 15 ft. Winds are forecast to remain in the 35 to 40 kt range through Wed before diminishing below gale force Wed night. Northerly 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 by Wed. 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 10N75W to 07N78W to low pres 1012 mb near 08N105.5W to low pres 1011 mb near 10.5N118W to 08N128W. The ITCZ continues from 08N128W to beyond 07.5N140W. Scattered moderate isolated strong convection is noted from 03N to 08N between 77W and 83W...including the approach to the Gulf of Panama, from 06.5N to 11N between 99W and 108W, and from 14.5N to 18N between 101W and 108W. Widely scattered moderate isolated strong convection is noted from 07.5N to 12N between 129W and 140W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for more on the Gulf of Tehuantepec gale force gap wind. NW swell continues to build across the waters of Baja California Norte, with seas currently in the 7-15 ft range. The swell will continue to propagate southward across the waters west of Baja California, peaking near 15 ft across the waters N of Punta Eugenia today. Seas greater than 8 ft will prevail through the week, then subside below 8 ft Sat. Light to gentle and variable winds prevail across the regional waters north of 21N this afternoon, produced by the weak pressure gradient related to deep layered low pressure and associated 1013 surface low near 29N123W, and just NW of the offshore waters. This surface low is expected to drift E through early Thu and weaken. As the low moves across the waters of Baja Norte expected gentle to moderate W to SW winds before the low moves inland late Wed night and weakens to a trough. Elsewhere, over the waters off SW Mexico, seas are in the 4-4 ft range. Seas there will build to 7-9 ft Wed through Thursday in a mix of large NW swell, and NE swell generated by the Gulf of Tehuantepec gale force gap wind event. Looking ahead, high pressure will build across the Baja offshore waters Thu and Thu night to bring a return to moderate northerly winds Thu night through Sat. 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 builds over the western Caribbean. Winds may reach near gale-force Wed through Wed night. 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 propagate over the waters off Guatemala and El Salvador, building seas of up to 10 ft through the middle of the week. Seas in the 4-6 ft range will prevail elsewhere. REMAINDER OF THE AREA... The pressure gradient between high pressure north of the area near 36N143W 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 120W. Deep layered low pressure has produced a 1013 mb surface low centered near 29N123W. The pressure gradient between the area of high pressure and this low is supporting fresh to strong winds west of the low. The low will drift E and gradually weaken through early Thu. Winds will decrease Wed as the low weakens. Long period NW swell is propagating over the NW portion of the forecast region, and will continue to spread SE across the forecast waters. Morning altimeter data showed seas 17-20 ft just north of the area, and 13-18 ft from 27N to 30N between 120W and 132W. This swell will bring seas greater than 12 ft over much of the waters north of 20N this afternoon. Seas greater than 8 ft with this swell will cover much of the waters west of 105W by Wed night. Seas will slowly subside, and fall below 8 ft over much of this area by Sat. $$ Stripling