000 AXPZ20 KNHC 202127 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Fri Dec 20 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 prevail across the Tehuantepec region with seas up to 16 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, as depicted by earlier altimeter passes. Seas are forecast to subside slightly today 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 low pressure on the coast of Colombia near 09N76W to 06N95W. The ITCZ continues from 06N95W to 09N113W to 08N125W to 09N140W. Scattered moderate and isolated strong convection is noted within 90 nm either side of the axis between 88W and 97W. Scattered moderate convection is noted within 120 nm either side of the axis between 102W and 110W, from 07N to 09N between 113W and 120W, and also from 08N to 10N between 136W and 140W. 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 1037 mb over the U.S. Great Basin region and a surface trough over NW Mexico is supporting fresh to strong NW winds across the Gulf of California. An ASCAT scatterometer pass recently 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 tonight through Sat, then again Tue night through Wed night, due to a locally tight pressure gradient. NW swell is propagating across the offshore waters of Baja California, with seas in the 7 to 10 ft range. Seas will subside to 6 to 8 ft tonight. Another set of NW swell will propagate into the area late tonight into early Sat, which will support seas in the 6 to 9 ft range through this weekend. 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 1025 mb is centered just N of the area near 33N123W. 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 18N 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 05N and W of 114W. A cold front has breached 30N140W and is moving SE. The front will reach from 30N136W to 27N140W by 21/0000 UTC this evening. Fresh to strong winds are expected on either side of the front, forecast to gradually dissipate as the front moves eastward during the weekend. This front will usher in a new set of long period NW swell, with seas peaking near 13 ft later 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