000 AXPZ20 KNHC 172152 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2152 UTC Fri Jan 17 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: High pressure over the Gulf of Mexico will maintain strong to minimal gale force N winds across the Tehuantepec region through Sun. Seas in excess of 8 ft continue to reach several hundred miles downstream of the Gulf, mixing with longer period NW swell. Looking ahead, a cold front will move across the Gulf of Mexico this weekend and induce a stronger and much broader gale wind event across Tehuantepec Sun night through Tue night, maybe diminishing Wed. N winds will peak between 35 and 40 kt, and seas between 16 and 17 ft. Winds will greatest during the overnight and early morning hours, when nocturnal drainage flow augments the winds. Papagayo region Gale Warning: A broad persistent ridge across the Caribbean and Central America is supporting strong to near gale force NE to E winds across and downstream of the Papagayo region, extending downstream to 240 nm. Winds will pulse to minimal gale force tonight and Sat night. Seas will peak between 10 and 12 ft 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 04N82W to 06N90W. The ITCZ continues from 06N90W to 05N96W to beyond 08N140W. Scattered moderate convection is noted from 06N to 08N between 130W and 135W. 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. A stalled frontal boundary extending from near Ensenada Mexico to past Guadalupe Island has weakened to a trough, and will likely dissipate altogether as it shifts southward tonight. High pressure is building behind this boundary off the coast of southern California, near 33N124W. A recent scatterometer satellite pass indicated winds have diminished off Baja California Sur over the past 24 hours, with concurrent altimeter satellite data showing 5 to 7 ft seas. A mid to upper level trough has been slowly moving eastward across the region north of 20N over the past couple of days, and is now just east of the Gulf of California. This has allowed cloud cover and shower activity to diminish accordingly. The high pressure off southern California along with strong high pressure building over the southern plains of the US will set up a fairly tight pressure gradient with the resident troughing along the Gulf of California. This will support fresh to strong winds tonight through Sat night over the central Gulf of California, and then Mon off Cabo Corrientes. Looking ahead, a new cold front will approach Baja California Norte and Guadalupe Island Tue and Tue night, accompanied by NW swell of 8-10 ft, before stalling and dissipating Wed. 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 Papagayo region. The pressure gradient responsible for the gap winds in southern Mexico and Central America is also supporting fresh to strong NE to E winds across the waters of northern Nicaragua and offshore of the Gulf of Fonseca, as well as fresh northerly winds in the Gulf of Panama. Winds across the Gulf of Panama and downstream to near 04N will increase each night this week, with downstream seas building to 6-7 ft by sunrise. REMAINDER OF THE AREA... Latest scatterometer data shows a large area of fresh trade winds W of 115W between 10N and 18N. Earlier altimeter passes showed seas of 8 to 10 ft, likely in mixed swell and NE to E wind waves. These winds have been diminishing as high pressure weakens ahead of a dissipating frontal boundary which entered the area north of 28N. The high pressure building behind the front will support a large area of fresh to strong trade winds south of 20N west of 120W tonight into Sat. Seas in this area will remain between 8 and 10 ft. Farther east, 8-9 ft seas persist between 06N-12N between 95W and 120W, due to swell originating from ongoing gap winds farther east in the Gulf of Tehuantepec and off the Nicaraguan coast. The synoptic pattern will change significantly early Sun, as a deep layer trough north of Hawaii shifts eastward. An associated surface low will drift eastward along roughly 25N, reaching 135W by late Sat into early Sun. Strong to near gale force SW winds, with seas to at least 12 ft may accompany this low within 360 nm radius on its southeast semicircle as it moves to the northeast. The low and associated weather is expected to move north of 30N by late Mon, leaving a trailing trough toward roughly 10N140W. Looking ahead, high pressure building along 25N in the wake of the exiting low pressure system may interact with the trough, to support fresh to strong NE winds between the ITCZ to around 20N west of 130W Tue and Wed. $$ Christensen