000 AXPZ20 KNHC 210311 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 311 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 0000 UTC surface analysis and satellite imagery through 0300 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Storm Warning: A strong cold front has moved across the western Gulf of Mexico and isthmus of Tehuantepec. Strong high pressure and dense cold air behind the front are supporting winds reaching at least 48 kt, the threshold for a storm warning, through the Gulf of Tehuantepec. An earlier scatterometer satellite pass confirmed this, with winds to 40 kt. In addition, land-based observations reported near gale sustained winds across the isthmus. Seas are estimated to be reaching 22 ft downstream of the Gulf of Tehuantepec, with seas in excess of 8 ft extending up to 600 nm downstream. 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 07N78W to 04N90W to 05N100W. The ITCZ begins near 05N100W and continues to 09N125W to 09N130W. Numerous moderate to isolated strong convection is noted from 05N to 09N between 82W and 88W. Scattered moderate convection noted from 06N to 10N between 120W 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 1019 mb high pressure centered near Guadalupe Island 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, as confirmed by recent ship observations. 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... A large area of showers and thunderstorms continues to be active off the coast of western Panama and Costa Rica. This activity is north of a surface trough extending east to west along roughly 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 is spreading 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... Earlier ship observations and a scatterometer satellite pass from 18 UTC indicated fresh to strong winds within 120 nm of a 1014 mb low pressure area centered near 29N126W. Recent altimeter satellite passes indicated seas to 10 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, dissipating 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. A mid to upper disturbance is interacting with trade winds convergence along the ITCZ between 120W and 125W to support scattered showers and thunderstorms. Farther west, a surface trough appears to be developing along the ITCZ near 135W, in an area of deep layer moisture situated to the southeast of a broad mid/upper trough. This is in a favorable area of further development, and fresh or even strong NE winds between the trough and high pressure building north of the area in the wake of the weakening low pressure near 29N126W. 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 14 ft near 30N140W, and seas greater than 8 ft will dominate west of 120W by Tue night. Looking ahead, the trough along the ITCZ will weaken through late week, leaving moderate to fresh trade winds across the tropics west of 120W. A cold front accompanied by a new round long- period NW swell will pass southwest of 140W by Sat. $$ Christensen