000 AXPZ20 KNHC 212205 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Tue Jan 21 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 2145 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: The edge of an afternoon Ascat pass suggested that strong gale force north to northeast winds are occurring across the Gulf of Tehuantepec and adjacent waters. Minimal gale force winds are well downstream of these winds to near downstream to near 13N96W. Maximum wave heights are up to around 19 ft within the area of the strong gale force winds, while the leading edge of waveheights greater than 8 ft in north to northeast swell reaches as far south as 04N98W. A tight pressure gradient associated with strong high pressure centered over southern Mexico will maintain the gale force winds in the Tehuantepec region through late tonight. These winds will begin to diminish Wed morning as the high pressure weakens and the tight gradient begins to slacken. Winds will further diminish through Wed afternoon as the high pressure over Mexico weakens further. Residual swell well downstream of the Gulf of Tehuantepec will decay by Thu afternoon. Marine interests transiting across or in the vicinity of the Gulf of Tehuantepec through tonight should take necessary action to avoid hazardous marine conditions. 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 this Gale Warning. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough axis extends from low pressure of 1007 mb over northwestern Colombia near 10N74W southwestward to the coast at 06N77W, and continues to 08N84W to low pressure of 1009 mb near 08N86W and to 04N91W to 04N102W, where latest scatterometer data indicates that it transitions to the ITCZ and continues to 06N115W to 07N127W and to beyond the area at 06N140W. Scattered moderate isolated strong convection is noted within 120 nm of low center in the SE semicircle, and within 120 nm north of the ITCZ between 135W and 140W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features above for details on an ongoing strong gale force gap wind event in the Gulf of Tehuantepec. High pressure of 1025 mb is located near 27N125W this afternoon, with an associated ridge extending southeastward across the Baja California Sur waters. Gentle to moderate northerly winds continue over the offshore waters between Cabo San Lazaro and Cabo Corrientes, as well as over the southern Gulf of California. Meanwhile, weakening low pressure, that this morning was roughly 120 nm west of Guadalupe Island, has moved southeastward as of early this afternoon to just west of offshore waters west of Punta Eugenia near 28N119W. The low will continue on a weakening trend and dissipate late tonight into early Wed. Moderate to fresh northerly winds will develop west of Baja California Wed into Thu as high pressure slides eastward along 29N/30N. Elsewhere, expect moderate to fresh northwest winds over the central and southern Gulf of California Wed night through Thu night as high pressure and associated tightening pressure gradient builds over the Great Basin region of the U.S. Long-period northwest swell is propagating through the Baja California Norte waters this morning, with seas expected to build to 8-10 ft north of Punta Eugenia tonight. The swell will propagate SE across the region and reach the Revillagigedo Islands Wed. Seas will gradually subside through Fri as the swell decays. Another round of long period northwest swell associated with an approaching cold front will reach the Baja California waters beginning late Fri night and build seas to 8 ft or greater there during the upcoming weekend. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Mainly scattered moderate convection is observed over the offshore waters of Costa Rica and western Panama this afternoon due to atmospheric instability from a 1009 mb low pressure centered near 08N86W. Showers and thunderstorms will likely continue through tonight, as the weak low persists offshore and the upper-level environment remains conducive for convection due to the passage of a Kelvin wave. Strong trades occurring over the southwestern Caribbean will continue to support strong to near gale force northeast to east winds over and downstream of the Papagayo region through Thu morning. Winds will be strongest during overnight and early morning hours assisted by nocturnal drainage. Waveheights will build to 10 ft each morning during the period of peak winds. Elsewhere, moderate to fresh northerly winds will continue in the Gulf of Panama region this week. Swell generated by a strong Tehuantepec gale force wind event will impact the Guatemala and El Salvador offshore waters through Wed, with seas 12 ft or greater continuing into tonight. REMAINDER OF THE AREA... The presence of the weak 1018 mb low centered near 28N119W, as described above, has disrupted the subtropical ridge over the area, resulting in weaker trades in the deep tropics east of about 125W. Farther west, a broad area of fresh to strong northeast winds is present roughly from 09N to 16N and west of 124W between the ITCZ and high pressure building across the far northwest portion of the area. These winds will likely continue for the next couple days as the subtropical ridge strengthens and low-level troughing remains north of the ITCZ roughly along 135W. Wave heights greater than 8 ft due to long-period northwest swell will dominate the region west of 117 by late tonight, with peak heights of around 11-14 ft associated with the strongest winds. By Thu afternoon, the leading edge of waveheights of 8 ft and greater is expected to have reach as far southeast as 98W. By early Thu, another set of long period northwest swell will reach the northwest part of the area, then propagate southeastward through the high seas during the upcoming weekend while gradually decaying. The culprit cold front is expected to be on the weak side as it moves across the far northern waters Sat and Sun. $$ Aguirre