000 AXPZ20 KNHC 222145 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Tue Dec 22 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. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from a 1010 mb low pressure over Colombia near 09N73W to 05N80W to 08N85W to 06N94W. The ITCZ axis extends from 06N94W to a 1009 mb low pressure located near 07N106W to 08N120W to 09N134W, then resumes W of a surface trough extending along 135W from 10N136W to beyond 09N140W. Clusters of moderate and isolated strong convection are noted near the low center from 06N to 09N between 104W and 109W. Scattered moderate to isolated strong convection is seen on either side of the trough axis from 07N to 12N between 128W and 139W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehunatepec: The most recent scatterometer pass provided observations of fresh to strong northerly winds in the Tehuantepec region and downwind to about 14N. These winds will persist through Wed morning with seas subsiding to 8 ft or less. A very strong gap wind event is in store for the Tehuantepec area beginning on Thu as a strong cold front moves across the Gulf of Mexico. Winds will begin to funnel into the Gulf of Tehuantepec by Thu afternoon, and rapidly increase to gale-force. Then, winds will further increase to minimal storm-force by Thu night into Fri morning. Marine guidance suggests northerly winds of 40-50 kt Thu night and Fri, with building seas in the 20-24 ft range. A Storm Warning will probably be issued tonight at 23/0600 UTC. Gale conditions are expected to persist into early Sat morning. Swell generated from this event will produce a large plume of 8 ft or greater seas that will affect the waters beyond 100W on Fri. Marine interests transiting across or in the vicinity of the Gulf of Tehuantepec should be aware of this upcoming gap wind event, and take necessary action to avoid hazardous marine conditions over the affected waters. Gulf of California: Gentle to moderate NW-N winds will prevail across the Gulf of California through Wed. Then, expect fresh to strong winds Wed night trough Thu night as a high pressure area settles over the Great Basin area of United States. These winds are forecast to spread southward beyond the entrance of the Gulf by Thu evening, when seas are forecast to briefly reach 8 ft mainly over the southern waters. Mainly gentle to moderate NW-N winds will prevail across the offshore waters of Baja California through Fri. Winds will increase to moderate to fresh mainly N of Cabo San Lazaro toward the upcoming weekend as the pressure gradient tightens some there between a ridge to the W and a meandering trough over the Gulf of California. Seas of 8 ft, generated by strong NW winds off the coast of California, will clip the waters of Baja California Norte on Wed. Large NW swell will move into the waters W of Baja California Sat night. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Fresh to strong NE-E winds will pulse across the Papagayo region through the next several days as high pressure remains in place over the W Caribbean. Looking ahead, swell generated during the upcoming Gulf of Tehuantepec gap wind event is expected to affect the offshore waters of Guatemala and El Salvador Thu night through Sat, with seas building up to 16-18 ft, especially Thu night and Fri. Gentle to moderate winds will prevail on either side of the monsoon trough E of 100W, with moderate to fresh winds W of 100W. REMAINDER OF THE AREA... High pressure located just N of the area dominates the forecast waters N of the ITCZ. The pressure gradient between the high pressure and lower pressures in the vicinity of the ITCZ is supporting moderate to fresh NE to E trades mainly from 09N to 20N W of 120W. Seas are in the 8-10 ft range based on altimeter data. As previously mentioned, a surface trough is within the ITCZ and extends along 135W from 07N to 12N. A strong convective activity was noted this morning in association with this trough. As a result, a scatterometer pass showed winds near gale-force in that region. The trough will move westward over the next 48 hours with an area of fresh to strong winds in the vicinity of it. A weak low pressure has developed along the monsoon trough near 07N106W. Visible satellite imagery confirmed the presence of the low center. This system will move westward over the next 48 hours with little change. An area of fresh to strong easterly winds will persist within about 90-120 nm in the northern semicircle of the low center, with seas in the 8 to 10 ft range. A cold front is forecast to enter the NW corner of the forecast region by Thu night. Fresh to strong SW winds are expected ahead of the front forecast to reach from 30N132W to 26N140W on Fri. Fresh northerly winds and very rough seas will follow the front. BY Fri night, the front will likely extend from 30N126W to 24N140W. Seas of 10-15 ft in NW swell are expected in the wake of the front at that time. $$ GR