000 AXPZ20 KNHC 180216 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 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 0000 UTC surface analysis and satellite imagery through 0215 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Storm Warning: Gale force winds in the Gulf of Tehuantepec are being ushered and funneled in behind a cold front just N of the area. Winds will further increase and reach minimal storm force by Wed 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 25 ft by Wed. Storm conditions will prevail through early Thu while gale conditions are then expected to continue through the weekend. Fresh swell generated from this event will produce a large plume of 12 ft or greater seas that will extent beyond 100W by 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. Gulf of California Gale Warning: Strong high pressure over the Great Basin region is supporting strong to minimal gale force winds across the Gulf of California, particularly across the northern Gulf, with seas currently up to 7 to 11 ft. Winds and seas will gradually decrease to 20 kt or less, with seas less than 8 ft by Wed afternoon as the high pressure moves eastward. 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 on both warnings. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from the Colombia/Panama border near 09N77W to 09N107W. The ITCZ continues from 09N107W to 07N125W to 07N140W. Scattered moderate and isolated strong convection is noted from 03N to 09N between 78W and 84W. Scattered moderate convection is noted from 06N to 10N between 121W and 129W, from 07N to 09N between 132W and 134W, and also from 08N to 10N between 135W and 140W. 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 region, and on the gale force wind event over the northern and central Gulf of California. The strong high pressure over the Great Basin region referenced above is also supporting fresh to locally strong to near gale force 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 on Wed. 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 Gulf of Tehuantepec will reach the offshore waters of Guatemala and El Salvador on Wed. The forecast calls for seas of 12 to 18 ft Wed and Wed night, and seas of 10 to 15 ft on Thu, then subsiding some by Thu night. Fresh to strong winds are expected across the Gulf of Papagayo Wed through Sun night with seas building to 8 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 cold front is over the NW forecast waters, extending from 30N127W to 24.5N140W. The front will gradually weaken while reaching from 30N122W to 25N130W to 24N140W on Wed, before dissipating by Thu. A large set of long period NW swell will propagate across the northern forecast waters in the wake of the front. High pressure behind the front will also bring increasing trade winds across the west- central waters Wed through Thu, mainly from 10N to 20N W of 130W. Seas of 8 ft or greater will dominate the waters W of a line from 30N115W to 20N118W to 10N122W to 05N140W on Thu morning. Another cold front will breach 30N140W by late Fri with fresh to strong winds both ahead of and behind it. The front will gradually weaken as it shifts eastward through the weekend, however, a reinforcing new set of NW swell will arrive behind it. $$ Lewitsky