000 AXPZ20 KNHC 202131 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2131 UTC Mon Jan 20 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 high pressure ridge across the eastern slopes of the Sierra Madre Mountains is maintaining a tight pressure gradient over southern Mexico. Recent observations indicate sustained winds to 30 kt at Salina Cruz on the Pacific coast of the Tehuantepec isthmus. This hints of much stronger winds farther offshore, likely near strong gale force. Seas are estimated at 18 to 20 ft currently downstream of the Gulf of Tehuantepec, and may build to 22 ft through this evening. Swell generated from this event will produce a plume of 8 ft or greater seas that will encompass much of the waters north of 03N and east of 105W by Tue night. Marine interests transiting across or in the vicinity of the Gulf of Tehuantepec through Tue night should take necessary action to avoid these hazardous marine conditions. Gales will continue through early Wed morning, then quickly diminish by Wed afternoon as the ridge weakens over eastern Mexico. 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 extends from near 06N77W to 06N110W. The ITCZ begins near 06N110W and continues to 08N130W to beyond 08N140W. Scattered moderate convection is noted from 06N to 08N between 82W and 86W. Scattered moderate to isolated strong convection noted from 07N to 10N between 123W and 125W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features above for more information on a strong gale force gap wind event in the Gulf of Tehuantepec. Weak high pressure centered over the Baja California offshore waters is maintaining light to gentle northerlies over the region, with moderate NW winds over the central and southern Gulf of California and near Cabo Corrientes. Outside of the Tehuantepec region, seas remain less than 8 ft throughout the forecast waters. A set of long period NW swell will reach the Baja California Norte waters on Tue, building seas to 10-11 ft. This swell will propagate SE across the region and reach the Revillagigedo Islands by Wed night. Seas will gradually subside through late week as the swell decays. Moderate to locally fresh northerly winds will develop offshore of Baja California Wed and Thu as high pressure builds NW of the region. Elsewhere, expect moderate to locally fresh NW winds across the central and southern Gulf of California Wed night through Fri as high pressure builds over the Great Basin region. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The latest GOES-16 satellite imagery and lightning data show scattered moderate isolated strong convection near a surface trough that extends across the offshore waters roughly along 05N. The passage of a Kelvin wave over this region is creating upper- level conditions that are conducive for enhanced convection, which will likely continue through Tue night. Strong trade winds across the SW Caribbean will continue to support strong to near gale force NE to E winds across and downstream of the Papagayo region through Thu morning. Winds will be strongest during the overnight and early morning hours with the assistance of the nocturnal drainage flow. Seas will build to 10 ft each morning during the period of peak winds. Elsewhere, moderate to fresh northerly winds will persist in the Gulf of Panama region this week. Swell generated by the strong Tehuantepec gale event will spread into the Guatemala and El Salvador offshore waters through Wed, with seas greater than 12 ft expected today through Tue night. REMAINDER OF THE AREA... Recent ship observations and a scatterometer satellite pass from 18 UTC indicated fresh to strong winds within 120 nm of a 1013 mb low pressure area centered near 28N127W. A concurrent altimeter satellite pass indicated seas to 11 ft near the low center. The low will weaken gradually as it continues to the east- northeast at 15 kt, allowing winds to continue to diminish near the low pressure. The low pressure will gradually dissipate through late Tue near Guadalupe Island. The presence of the low center over the subtropical region has disrupted to the typical subtropical ridge over the area, resulting in only moderate trade winds over the deep tropics east of 130W. This is well evident in latest scatterometer data and buoy observations. Recent altimeter satellite data shows seas of 8 to 9 ft in the area of moderate trades. The trade winds will increase Farther west, the mid/upper disturbance supporting the low center is also reaching into the deep tropics and supporting clusters of showers and thunderstorms along the ITCZ west of 130W. A trough may be forming between 130W and 135W north of the ITCZ to near 15N. Fresh to possibly strong NE winds are expected to develop west of the surface trough as high pressure builds north of the region in the wake of the low center through mid week. Looking ahead, this will diminish through late week, allowing a broad area of moderate to fresh trades south of 18N to the ITCZ. Meanwhile a new set of long period NW swell entering the NW waters will propagate SE across the high seas for the next several days. Seas will peak around 15 ft near 30N140W today, and seas greater than 8 ft will dominate west of 120W by Tue night. $$ Christensen