000 AXPZ20 KNHC 222128 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Sun Dec 22 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 Gale Warning: The pressure gradient between a ridge across the eastern slopes of the Sierra Madre Oriental in Mexico and the equatorial trough in the eastern N Pacific continues to support gale force northerly gap winds across the Tehuantepec region, with seas up to 15 ft. The area of high pressure will build further through tonight in the wake of a frontal boundary in the SW Gulf of Mexico. This will tighten the pressure gradient across the area and increase winds to 40 to 45 kt over the Gulf of Tehuantepec later tonight, with seas building up to near 20 ft. High pressure will start to weaken and shift eastward for the remainder of the early part of the week. This will loosen the pressure gradient, and veer winds over the SW Gulf of Mexico. The loosened gradient and veered winds will help diminish winds and bring this extended gale force gap wind event to an end by Tue afternoon. Swell generated from these ongoing gap winds continue to produce a large plume of 8 ft or greater seas that extends beyond 100W. 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 1007 mb low pressure in the Gulf of Panama near 08N79W to 08N90W to 09N98W to 1009 mb low pressure near 07N101W to 06N106W. The ITCZ continues from 06N106W to 09N120W to 07N135W to 08N140W. Scattered moderate and isolated strong convection is noted from 05N to 10N to the E of 87W, including the Gulf of Panama, and from 08N to 11N between 95W and 101W. Scattered moderate convection is noted from 06N to 08N between 113W and 117W, and from 06N to 08N between 133W and 137W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for details about the ongoing gale force gap wind event across the Gulf of Tehuantepec. Seas of 8 ft or greater in NW well prevail across the offshore waters W of Baja California. This swell event will subside on Mon. On Tue, a cold front will move across the area bringing an increase in winds and seas. Expect fresh to locally strong W to NW winds and building seas of 8 to 9 ft. Another cold front is forecast to move across Baja California Norte into the northern Gulf of California on Thu bringing an an increase in winds and seas. A larger set of NW swell will follow the front, with seas building to 12 to 16 ft N of Punta Eugenia, and to 8 to 14 ft between Cabo San Lazaro and Punta Eugenia by Thu night. Fresh to strong NW winds will develop offshore of Cabo Corrientes by mid-week due to a locally tight pressure gradient between a ridge extending eastward to beyond the Revillagigedo Islands and lower pressures over north-central Mexico. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Seas generated by a gale force gap wind event in the Tehuantepec region will continue to propagate across the offshore waters of Guatemala and El Salvador through Tue. Seas will start to subside to less than 8 ft by Tue night. Fresh to strong winds and building seas are expected across the Gulf of Papagayo and downwind to near 90W through the next several days, pulsing to near gale force during the overnight and early morning hours through at least Tue. 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 extends over the N waters from 30N121W to 21N130W to 18N140W. Winds behind the front have diminished, however it has ushered in a new set of long period NW swell with seas up to around 12 ft. The front is forecast to gradually dissipate while moving eastward reaching the offshore forecast waters of Baja California on Mon. High pressure is building in the wake of the front, tightening the pressure gradient and increasing trades across the W central waters. These trades will continue through at least Wed. Another cold front will drop down S of 32N by late Mon with a surge of fresh to strong NW winds behind it. Long period NW swell propagating across the area E of the front as well, mixing with shorter period wind waves, supporting seas in the 9 to 11 ft range S of the front over the W central waters. The NW swell is also helping to maintain seas of 8 ft or greater over much of the remaining waters N of 07N and W of 110W. $$ Lewitsky