000 AXPZ20 KNHC 212120 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Sat Dec 21 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 2045 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A ridge across the eastern slopes of the Sierra Madre Oriental in Mexico continues to support gale force northerly gap winds across the Tehuantepec region, with seas up to 15 ft. High pressure will build on Sun in the wake of another cold front moving across the 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 by Sun evening with seas building up to 19 ft. High pressure will start to weaken and shift eastward early next 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 early Tue. 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 eastern Panama near 08N78W to 06N85W to 08N95W to 06N102W. The ITCZ continues from 06N102W to 08N126W to 08N140W. Scattered moderate and isolated strong convection is noted within 180 nm SE of the axis E of 85W, from 05N to 08N between 87W and 93W, and from 06N to 13N between 93W and 102W. Scattered moderate convection is noted from 07N to 09N between 131W 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. Gulf of California: The pressure gradient between high pressure over the U.S. Great Basin region and surface troughing over western Mexico is supporting moderate to fresh NW winds across the Gulf of California. The area of high pressure will shift E of the Great Basin region tonight loosening the pressure gradient across the Gulf of California, and diminishing winds. NW swell will prevail across the offshore waters W of Baja and N of Cabo San Lazaro with seas of 6 to 9 ft. This swell will subside early next week. A larger set of NW swell will arrive towards the end of the week, with seas building to 8 to 14 ft by Thu night. NW winds at fresh to strong will develop offshore of Cabo Corrientes by mid-week due to a locally tight pressure gradient associated with a decaying frontal boundary dropping SE. These winds are forecast to briefly increase to gale force Wed night. 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 early next week. Fresh to strong winds and building seas are expected across the Gulf of Papagayo and downwind to near 90W through next week, pulsing to near gale force at night through the early part of the week. 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 NW waters from 30N129W to 25N134W to 21N140W. The most recent scatterometer pass indicates fresh to strong winds on either side of the front. The front has ushered in a new set of long period NW swell. Seas are currently peaking near 14 ft W of the front based on earlier altimeter data. The front is forecast to gradually dissipate while moving eastward into early next week. High pressure will build in the wake of the front. This will tighten the pressure gradient, and increase trades across the west-central waters into early next week. Another cold front will drop down S of 32N by late Mon with a surge of fresh to strong NW winds behind it. Elsewhere, a ridge dominates the remainder of the N waters. The pressure gradient between the ridge and lower pressure in the vicinity of the ITCZ supports an area of moderate to fresh trades N of the ITCZ to about 20N and W of 120W. Long period NW swell propagating across the area is mixing with shorter period wind waves, supporting seas in the 9 to 11 ft range over this area. 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