000 AXPZ20 KNHC 210249 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 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 0000 UTC surface analysis and satellite imagery through 0215 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Gale force northerly gap winds prevail across the Tehuantepec region with seas up to 14 ft. Winds are forecast to increase to strong gale levels by Sun night as the next cold front moves by N of the area in the Gulf of Mexico with high pressure strengthening in the wake of the front. These increasing winds will build seas to up to 20 ft Sun night. Gale force winds are then forecast to persist through early Tue before finally diminishing slightly. 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 over northern Colombia near 10N75W to 07N81W to 08N90W to 06N98W to 1010 mb low pressure near 08N109W to 08N111W. The ITCZ continues from 08N111W to 08N125W to 08N140W. Scattered moderate and isolated strong convection is noted from 05N to 08N between 90W and 98W, and also from 08N to 10N between 134W and 137W. Scattered moderate convection is noted from 08N to 12N between 105W and 112W. 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 of 1036 mb over the U.S. Great Basin region and surface troughing over the Baja California Peninsula continues to support fresh to strong NW winds across the Gulf of California. An earlier ASCAT scatterometer pass confirmed these conditions. The area of high pressure will shift E of the Great Basin region through Sat. This will loosen the pressure gradient across the Gulf of California, and diminish winds Sat. Winds will pulse to fresh to strong near Cabo Corrientes late tonight into early Sat, then again Tue night through Wed night, due to a locally tight pressure gradient. NW swell is propagating into the offshore waters of Baja California, with seas building to 7 to 10 ft overnight. This set of swell will subside Sun into early next week. Yet another set of NW swell is likely to arrive by 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 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... High pressure of 1022 mb is centered near 28N124W. The pressure gradient between the area of high pressure and lower pressure in the vicinity of the ITCZ supports an area of moderate to fresh trades N of the ITCZ to 20N and W of 122W. Long period NW swell propagating across the area is mixing with shorter period wind waves, supporting seas in the 9 to 12 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 112W. A cold front has breached 30N140W, currently extending from 30N136W TO 27N140W, with fresh to strong winds on either side of the front. The front is forecast to gradually dissipate as the while moving eastward during the weekend, while ushering in a new set of long period NW swell, with seas peaking near 13 to 14 ft tonight. 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 front will drop down S of 32N by late Mon with a surge of fresh to strong NW winds briefly behind it. $$ Lewitsky