818 AXPZ20 KNHC 191000 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Mon Dec 19 2022 Tropical Weather Discussion for the eastern Pacific Ocean from 03.4S to 30N, east of 120W including the Gulf of California, and from the Equator to 30N, between 120W and 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis. Based on 0600 UTC surface analysis and satellite imagery through 0945 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: High pressure will build southward along the eastern slopes of the Sierra Madre Mountains starting late on Tue as a western Gulf of Mexico low pressure system shifts eastward. As this happens, the gradient in southeastern Mexico will tighten as cold dense air surges southward toward the Gulf of Tehuantepec gap region. The resultant surge of northerly winds out over the Gulf will reach gale-force in the range of 30-35 kt on Tuesday night, and is expected to last through Wed night. Seas are forecast to build to 8-11 ft. Northerly winds will be strong to near gale- force during Wed afternoon and night. Seas will subside to a peak of about 9 ft late Wed night. Please read the latest High Seas Forecast issued by the the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 07N79W to 08N90W and to 07N102W. ITCZ extends from 07N102W to 08N116W to 06N131W to beyond 07N140W. Scattered moderate convection is within 60 nm south of the trough between 84W-85W, also between 86W-88W and within 60 nm north of the trough between 93W-95W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information about an upcoming gale event in the Gulf of Tehuantepec. Relatively weak high pressure is over the area as depicted by the latest scatterometer data that shows light to gentle winds continuing to prevail across the Baja California offshore waters, Gulf of California, and southwest Mexico. Seas across these waters range 3-4 ft, except for lower seas of 1-2 ft in the Gulf of California. The latest scatterometer data nicely depicted strong northerly winds in the Gulf of Tehuantepec. Seas are likely peaking to 8 t in that area. Light to gentle winds prevail elsewhere in the southern Mexico offshore waters with 4-5 ft seas. For the forecast, strong to near gale northerly winds will continue through in the Gulf of Tehuantepec through early this afternoon, at which time the pressure gradient in eastern Mexico relaxes. Seas will lower to below 8 ft by late this morning. Conditions will rapidly improve on Mon afternoon. Strong northerly winds will return to the Gulf of Tehuantepec by Tue afternoon as strong high pressure surges southward over eastern Mexico. Gale-force winds are expected with this event starting Tue evening and continuing through Wed night. Seas may build to near 12 ft Tue night into Wed. Conditions will improve on Thu afternoon briefly before a strong gap wind gale event begins on Fri. This next event could very well reach storm force. Please monitor the latest marine forecasts for future updates regarding this next upcoming Gulf of Tehuantepec gap wind event. Meanwhile, strong NW winds are expected to develop in the Gulf of California tonight as strong high pressure builds over the western U.S. The high pressure will weaken on Wed allowing for these winds to diminish to fresh speeds. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh to strong northeast to east winds are present in the Gulf of Papagayo region, extending westward to near 90W. Seas are peaking to 7 ft over these waters. Light to gentle variable winds prevail elsewhere north of the monsoon trough with 3-4 ft. Light to gentle S-SW winds and seas of 4-5 ft due to a S to SW swell are found south of the monsoon trough. Gentle or weaker winds and slight to moderate seas are noted across the central American offshore waters. For the forecast, fresh to strong northeast to east winds will continue in the Papagayo region through the rest of the week due to the pressure gradient related to high pressure ridging NE of the region. The strong winds are mainly expected at night and into the mornings. Seas are expected to build near 8 ft at the time of the strong winds. Moderate to locally fresh northerly winds likely tonight and Mon night in the Gulf of Panama. Gentle winds will continue across the Central American offshore waters through most of the week along with moderate seas. REMAINDER OF THE AREA... A rather ill-defined surface trough extends from 28N122W southwestward to near 24N129W. Isolated, light showers are possible near the trough. Latest scatterometer data shows gentle to light NW-N winds north of the trough. The remainder of the area remains under the control of relatively weak high pressure. The tail-end of a cold front is just NW of the area. Latest scatterometer data shows mostly fresh southeast to south winds N of 24N and west of about 135W. Seas of 8 ft due to a long-period W-NW swell are within this area. Elsewhere, light NE-E winds are present N of 19N and W of 120W, except for light to gentle N-NE winds between the low and 120W. Seas over this area are 5-6 ft. Moderate to locally fresh winds are noted from the ITCZ to 19N and W of 115W, with gentle to moderate southerly winds south of the ITCZ. Seas are in the range 5-7 ft, except for slightly higher seas of 6-8 ft in the far western part of the area from 05N to 16N W of 134W that are due to a long-period NW swell. Elsewhere, moderate or weaker winds with slight to moderate seas are prevalent. For the forecast, moderate to locally fresh trade winds S of 20N and W of 120W are expected to change little through Wed night. The long-period swell in the far western part of the area will migrate E to near 120W by Wed night. Looking ahead, high pressure will shift eastward while strengthening through Wed night. The gradient between the high pressure and relatively low pressure in the tropics should allow for fresh trade winds to exist S of 20N and W of 120W through Wed night. A complex low pressure system and associated cold front will approach the NW waters on Tue night into Wed, bringing strong to near gale-force southerly winds N of 26N and W of 137W on Wed afternoon. A low probability presently exists for these winds to reach sustained gale-force speeds. Large swell producing seas possibly to 17 ft will also propagate through this area Tue night through Wed night, then begin to slowly subside on Thu. $$ Aguirre