000 AXPZ20 KNHC 190404 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 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 0000 UTC surface analysis and satellite imagery through 0400 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 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 morning. 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 from 09N85W to 07N93W and to 06N103W. ITCZ extends from 06N103W to 07N115W to 07N130W to beyond 07N140W. Scattered moderate convection is within 30 nm south of the trough between 85W-89W. 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, with 1-2 ft in the Gulf of California. The latest scatterometer data also showed 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 Mon afternoon, at which time the pressure gradient in eastern Mexico relaxes. Seas will lower to below 8 ft by late Mon 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 morning. Seas may build to near 12 ft Tue night into Wed. Conditions will improve on Thu afternoon briefly before the next gap wind event begins on Fri. Meanwhile, strong NW winds are expected to develop in the Gulf of California Mon night 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 easterly breezes are present in the Gulf of Papagayo region, extending westward to 89W. Seas are 6 ft in 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 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, moderate to fresh easterly winds will continue in the Papagayo region through the upcoming week, pulsing to strong at night due to the pressure gradient related to high pressure ridging NE of the region. 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 with moderate seas. REMAINDER OF THE AREA... A weak 1015 mb low pressure is centered near 27N123W, with a surface trough extending southwestward to near 25N130W and northeastward to near 29N121W. Isolated, light showers are possible near the low and trough. Latest scatterometer data shows gentle to moderate NE winds northwest of the low, and gentle to light NW-N winds north of the trough. The remainder of the area remains under the control of relatively weak high pressure. A cold front has recently encroached into the far western waters along a position from 30N139W south-southwest to west of the area at 26N140W. Latest scatterometer data shows mostly fresh southeast to south winds N of 28N and west of about 138W. 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 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 E while strengthening through early next week. This will yield a broad zone of fresh tradewinds S of 20N and W of 120W starting Tue and continuing through most of the week. Another frontal system will approach the NW waters on Tue night into Wed, bringing strong winds and potential gale force winds N of 26N and W of 137W on Wed afternoon. Large swell, with seas building to near 20 ft will also propagate through this area Tue night through most of the week. $$ Aguirre