000 AXPZ20 KNHC 182148 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Wed Dec 18 2019 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 2030 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Storm Warning: Storm force northerly gap winds are blowing across the Tehuantepec region behind a cold front currently located near the Yucatan Peninsula. Storm conditions will prevail through early Thu, while gale conditions are expected to continue through the weekend and into early next week. Very large seas will develop with these winds, between 20 and 25 ft. Swell generated from this event will produce a large plume of 12 ft or greater seas that will extent beyond 100W tonight into Thu morning. Marine interests transiting across or in the vicinity the Gulf of Tehuantepec over the next several days should be aware of this significant gap wind event, and take necessary action to avoid hazardous marine conditions over the affected waters. Please see the latest High Seas Forecast issued by the National Hurricane Center under AWIPS/WMO headers HSFEP2/FZPN03 KNHC or at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for further details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from eastern Panama near 08.5N78.5W to 05N95W to low pressure near 08N112W to 08N115W. The ITCZ continues from 08N115W to 08N123W to 07N140W. Scattered moderate and isolated strong convection is noted from 04N to 10N east of 86W, and also from 08N to 10N between 127W and 133W. Scattered moderate convection is noted from 07N to 09N between 109W and 116W, and also from 06N to 13N between 116W and 122W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for details on the storm force gap wind event across the Gulf of Tehuantepec. Gulf of California: Strong high pressure over the Great Basin region continues to support fresh to strong NW winds across the Gulf of California, with seas currently to 8 ft. Winds and seas will gradually decrease to 20 kt or less, with seas less than 8 ft by this evening as the high pressure moves eastward. A large set of long period NW swell, behind a dissipating cold front, will bring seas of 8 to 12 ft across the offshore waters W of Baja and N of Cabo San Lazaro by early Thu. This swell event will reach the Revillagigedo Islands late this week. Another set of NW swell is expected this weekend into early next week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Seas generated by a storm gap wind event in the Tehuantepec region will propagate across the offshore waters of Guatemala and El Salvador through Fri night. The forecast calls for seas of 12 to 18 ft through Thu, and seas of 8 to 12 ft on Thu night. Seas in northerly swell will build again to 10 to 15 ft on Sun as winds likely increase to near storm force in the Tehuantepec area. Fresh to strong winds are expected across the Gulf of Papagayo through the next several days, with seas building to 10 ft. Elsewhere, gentle to moderate south to southwest monsoon flow will persist across the offshore waters of Costa Rica, Panama, Colombia, and Ecuador, while light to gentle flow will dominate across the Gulf of Panama. REMAINDER OF THE AREA... A weakening cold front extends from 30N121W to 24N130W to 22.5N140W. The front is forecast to dissipate over the forecast waters on Thu. A large set of long period NW swell will propagate across the northern forecast waters in the wake of the front. Seas of 8 ft or greater will dominate the waters W of a line from 30N115W to 20N118W to 10N122W to 06N140W on Thu morning. High pressure behind the front is also bringing increasing trade winds across the west-central waters tonight through Thu, mainly from 10N to 20N W of 130W. Another set of long period NW swell is expected this weekend in association with a cold front approaching 30N140W by Fri morning. Fresh to strong winds are expected on either side of the front. The front will dissipate as it moves eastward during the weekend. High pressure will build in the wake of the front NW of 30N140W, helping to increase trades yet again across the west- central waters into early next week. $$ Lewitsky