000 AXPZ20 KNHC 162148 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2148 UTC Thu Jan 16 2020 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: A ridge across the eastern slopes of the Sierra Madre Oriental of Mexico continues to drive strong to minimal gale force northerly winds across the Tehuantepec region. Winds are greatest during the overnight and early morning hours with the assistance of the nocturnal drainage flow. Associated seas will build 11 to 12 ft during the periods of gales. Seas in excess of 8 ft continue to reach several hundred miles downstream, mixing with longer period NW swell. A cold front will move across the Gulf of Mexico this weekend and induce a strong and much broader gale event across Tehuantepec late Mon through Tue. Looking ahead to early next week, the high pressure will intensify behind a stronger cold front, with northerly winds of 35 to 40 kt and seas of 16 or 17 ft. Gulf of Papagayo Gale Warning: A broad and persistent ridge across the Caribbean and Central America is supporting strong to near gale force NE to E winds across and downstream of the Gulf of Papagayo region, to include much of the coast of Nicaragua, and extending downstream out to 240 nm. Winds will briefly pulse to minimal gale force late Fri night into Sat morning. This general pattern will persist through the upcoming weekend. Seas will build to 10 to 11 ft each night during the period of peak winds. Please see the latest High Seas Forecast issued by the National Hurricane Center under AWIPS/WMO headers FZPN03 KNHC/HSFEP2 or at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for further details on these two Gale Warnings. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from near 05N78W to 05N100W. The ITCZ continues from 05N100W to 07N140W. No significant convection is observed. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see above for more on the latest gale force gap wind event in the Gulf of Tehuantepec. Elsewhere, a ridge extends from a 1021 mb high pressure located near 28N122W to near Socorro Island. Ship observations indicate an area of fresh to strong winds off Baja California Sur. This is part of a large plume of strong winds reaching from the peninsula to past Clarion Island, in a relatively tight pressure gradient between the high pressure and weak troughing south of Socorro Island. Seas are estimated to be around 7 to 9 ft in this area of strong winds. An upper disturbance west of Baja California continues to produce unsettled weather over Baja California Sur and the central and southern Gulf of California, possibly with a few embedded rain showers. These winds will diminish into this evening as the high pressure weakens ahead of a weak cold front approaching Baja California Norte from the north Pacific. New high pressure building behind this front through Fri will support fresh NW winds north of Punta Eugenia, and fresh to strong NW winds over the central Gulf of California late Fri through late Sat. As these winds diminish Sun into Mon, winds may increase to 20 to 25 kt farther south off Cabo Corrientes. Looking ahead, a new cold front will approach northern Baja California Norte and Guadalupe Island Tue and Tue night, accompanied by NW swell of 8 to 10 ft. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Please see above for more on the latest gale force gap wind event in the Gulf of Papagayo. The pressure gradient responsible for the gale force gap wind events in Tehuantepec and Papagayo regions is also supporting strong NE to E winds across the waters of northern Nicaragua and offshore of the Gulf of Fonseca, as well as fresh to strong northerly winds across the Gulf of Panama. Fresh northerly winds across the Gulf of Panama and downstream to near 04N will increase to strong each night through the morning hours this week, with downstream seas building to 6 to near 8 ft each night. REMAINDER OF THE AREA... A recent scatterometer pass from 18 UTC indicated a large area of fresh to strong trade winds between 10N and 18N, due south of 1021 mb high pressure centered near 28N122W. Concurrent altimeter passes showed seas reaching 12 ft in this area, likely due to NW swell mixing with shorter period easterly energy from the trade wind flow. The winds are the result of a tight pressure gradient between the high pressure and a surface trough south of Socorro Island. These winds will diminish through late today as the high pressure weakens ahead of a cold front entering the waters north of 28N. The front will stall then dissipate through tomorrow. But high pressure building behind the front will support a large area of fresh to strong trade winds south of between the ITCZ and 20N west of 120W Fri into Sat. Seas in this area will be 8 to 10 ft. Farther east, 8 to 9 ft seas persist between roughly 06N and 12N between 95W and 120W, mostly due to shorter period easterly swell originating from ongoing gap winds farther east in the Gulf of Tehuantepec and off the Nicaraguan coast. The pattern will change going into Sun as a deep layer trough north of Hawaii shifts eastward toward the forecast area. An associated surface low will shift eastward along roughly 25N, reaching 135W by late Sat into early Sun. Strong to near gale force winds, along with seas to at least 12 ft may accompany the low pressure within 360 nm radius on its southeast semicircle as it moves to the northeast. The low pressure and its associated weather is expected to move north of 30N by late Mon, leaving a trailing trough toward roughly 10N140W. Looking ahead, as high pressure builds in the wake of the low pressure, fresh to strong NE winds can be expected to develop along this trough, mainly south of 15N Mon into Tue. $$ Christensen