000 AXPZ20 KNHC 181531 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1404 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Storm Warning: Strong gale force gap winds are blowing across the Tehuantepec region behind a cold front currently located over the Yucatan Peninsula. Winds will further increase and reach minimal storm force later this morning as high pressure continues to build behind the front across the eastern slopes of the Sierra Madre Mountains in Mexico. Storm conditions will prevail through early Thu while gale conditions are expected to continue through the weekend. Very large seas will develop with these winds reaching between 20 and 23 ft later today. 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 a 1007 mb low pressure near 10N77W to 06N95W to 08N113W. The ITCZ continues from 08N113W to 08N130W to 06N140W. Scattered moderate isolated strong convection is noted N of 04N E of 83W to the coast of Colombia, and from 07N to 10N between 118W and 124W. 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 afternoon as the high pressure moves eastward. The strong high pressure over the Great Basin region referenced above is also supporting fresh to locally strong NE winds across the Baja California Norte mountain passages and over the subsequent downwind offshore waters W of Baja California, particularly from 26N to 29N E of 117W. Winds will diminish 20 kt or less later this morning. 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 Thu morning. This swell event will reach the Revillagigedo Islands late this work week. Another set of NW swell is expected this weekend. 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 reach the offshore waters of Guatemala and El Salvador this morning. The forecast calls for seas of 12 to 18 ft today 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 tonight through Sun night 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 30N122W to 25N130W to 23N140W. 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 today 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. $$ GR