000 AXPZ20 KNHC 192109 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Thu Dec 19 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 2100 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Strong gale force northerly gap winds are now blowing across the Tehuantepec region with seas up to 21 ft. Similar marine conditions are expected to persist through the weekend and into early next week. Swell generated from this event is currently producing a large plume of 12 ft or greater seas that extends beyond 100W. Seas are forecast to subside some on Fri before rebuilding late this weekend. Marine interests transiting across or in the vicinity the Gulf of Tehuantepec over the next several days should be aware of this strong 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 1006 mb low pressure near the coast of Colombia at 11.5N75W to 08N80W to 05N99W. The ITCZ continues from 05N99W to a 1010 mb low pressure near 07N111W to 08.5N124W to 07N132W to 08N140W. Scattered moderate convection is noted from 07N to 09N between 78W and 84W, within 90 nm in the NE quadrant of the low near 07N111W, from 04N to 11N between 120W and 129W, and also from 07N to 09N between 132W and 140W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for details on the gale force gap wind event across the Gulf of Tehuantepec. Gulf of California: Building high pressure in the U.S. Great Basin region is supporting fresh to strong NW winds and building seas across the Gulf which will continue through Sat morning. Expect fresh to strong winds and seas to around 8 ft. A large set of long period NW swell will bring seas up to 11 ft across the offshore waters W of Baja and N of Cabo San Lazaro today. This swell event will reach the Revillagigedo Islands Fri. 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 strong gap wind event in the Tehuantepec region will continue to propagate across the offshore waters of Guatemala and El Salvador through early next week. The highest seas up to 15 to 17 ft are expected today, subsiding some Fri through Sat, and building again up to 13 to 14 ft by early next week. Gulf of Papagayo: Fresh to strong winds are expected across the Gulf of Papagayo and downwind to near 90W over the next several days, occasionally near gale force. Seas will build to 8 to 11 ft with these winds. Gulf of Fonseca: Fresh to strong NE winds will pulse tonight, then moderate to fresh thereafter. 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... High pressure of 1025 mb located near 32N126W dominates the northern forecast waters. The pressure gradient between the high pressure and lower pressure in the vicinity of the ITCZ supports and area of fresh to strong trades mainly from 10N-20N W of 128W. Latest altimeter passes indicated seas of 10 to 12 ft within the area of these winds. The aerial extent and the strength of the trade will decrease on Fri as the high pressure moves eastward and a strong cold front reaches the NW corner of the forecast area. The front will be near 30N140W by early Fri afternoon, and extend from 30N136W to 27N140W by Fri evening. Fresh to strong winds are expected on either side of the front, forecast to gradually dissipate as it moves eastward during the weekend. A new set of long period NW will follow the front. 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. Meanwhile, seas of 8 ft or greater dominate much of the forecast waters W of 110W due to long period NW swell, and E of 110W in association with the strong gap wind events in the Gulf of Tehuantepec and Gulf of Papagayo. Little change is expected during the upcoming weekend and into early next week. $$ Lewitsky