000 AXPZ20 KNHC 181000 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 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 0600 UTC surface analysis and satellite imagery through 0900 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 N of the area. 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 25 ft by Wed. 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. 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 07N78W to 05N90W to 08N107W. The ITCZ continues from 08N108W to 08N122W to 07N140W. Scattered moderate and isolated strong convection is noted from 04N to 09N E of 84W. Scattered moderate convection is from 07N to 09N between 116W and 125W. 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. Gulf of California: Strong high pressure over the Great Basin region is supporting strong to near gale force winds across the Gulf of California, particularly across the northern Gulf, with seas currently up to 10 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 11 ft across the offshore waters W of Baja Norte by tonight and N of Cabo San Lazaro by Thu morning. The swell event will reach the Revillagigedo Islands by Fri. 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 this morning. The forecast calls for seas of 12 to 18 ft today and tonight, 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 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 30N124W to 25N132W. The front will gradually weaken while reaching from 30N119W to 23N130W tonight, 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 today through Thu, mainly from 10N to 20N W of 130W. 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. $$ Ramos