000 AXPZ20 KNHC 190932 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Thu Sep 19 2024 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 0830 UTC. ...TROPICAL WAVES... A western Caribbean tropical wave is along 82W-83W, extending southward across the Costa Rica/Panamanian border to the eastern Pacific waters north of 05N. It is moving west at 5 kt. Scattered moderate to strong convection described below covers the Pacific waters N of 07.5N and inland across Central America E of 91W. A tropical wave is along 98W-99W, extending from southeastern Mexico southward over the eastern Pacific waters to near 04N, moving west at about 10 kt. Scattered to locally numerous moderate to strong convection described below is N of 07.5N to coastal Mexico between 93W and 102W. A tropical wave is along 116W-117W from from 05N to 19N, moving west at 10 kt. Scattered moderate isolated strong convection described below is from 07.5N to 13.5N between 110W and 120W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 10.5N73W to 10.5N96W to 11.5N104W to 08.5N126W to 10N140W. Scattered to locally numerous moderate to strong convection is noted from 03.5N to 07.5N E of 79W, from 07N to 16.5N between 82W and 111W, and from 07.5N to 13.5N between 111W and 129W. Scattered moderate isolated strong convection is noted from 07.5N to 14N between 134W and 140W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A broad surface ridge extends southeastward into the region through 27N130W to offshore of SW Mexico near 17N108W. Over the near and offshore waters of Baja California, gentle to moderate NW winds prevail, and extend southward to 20N, except for fresh winds near the coast between Punta Eugenia and Cabo San Lazaro. South of 20N through the Revillagigedo Islands and to Michoacan, Mexico, gentle winds gradually become nw to N. Seas are generally 4 to 5 ft in moderate period swell except to 6 ft in the areas of fresh winds. Light to gentle W to SW winds cover the remaining waters eastward to Tehuantepec. Seas south of 20N are to 4 to 5 ft in long period SW swell E of 105W and in NW swell W of 105W. Scattered showers and thunderstorms continue to shift SW off the coast and over the coastal waters within 150 nm of the Mexican coast between Tehuantepec and Colima. Light to gentle S to SW winds are over the north and central portions of the Gulf of California, with moderate W to SW gap winds occurring across typical locations over northern and southern sections of the Gulf. Seas are 1 to 3 ft over the Gulf of California, except 3 to 4 ft in SW swell over the entrance to the Gulf. For the forecast, the current Pacific ridge will remain in place and fluctuate into the upcoming weekend This pattern will maintain moderate NW to N winds over the offshore waters of Baja California tonight, gradually weakening through Thu afternoon. Expect fresh winds near the coast each evening. High pressure will strengthen modestly Fri and Sat to bring a return to moderate to fresh winds. Variable winds less than 15 kt are expected across the Gulf of California, except for pulses of moderate W gap winds across southern portions and fresh SW gap winds N of 30N each evening and night through Fri. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gentle to moderate SW to W winds prevail south of the monsoon trough, along about 10N-11N. North of the monsoon trough, moderate or weaker winds are observed. Seas are 4 to 5 ft in SW swell except to 6 ft south through west of the Galapagos Islands. A nearly solid line of strong thunderstorms has moved westward off the coasts from southern Costa Rica to El Salvador and Guatemala during the past few hours, producing frequent lightning and gusty easterly winds. This activity continues at this time. For the forecast, gentle to moderate SW to W winds will continue south of the monsoon trough near 11N, through this afternoon, then begin to freshen offshore through Sat. Seas will build to 5 to 7 ft during this time in a mix of SW swell and westerly wind swell. North of 11N, moderate or weaker winds are expected through Thu evening before the monsoon trough begins to lift northward, and winds shift to westerly and gradually increase to gentle to moderate by Sat. The monsoonal flow is expected to become very active, and dominate the region into early next week, as a long fetch of westerly winds sets up from the offshore waters to 110W. This pattern will generate increasing westerly wind waves moving into the area waters. Active weather is also expected across area waters N of 06N Fri through the weekend. ...REMAINDER OF THE AREA... Surface ridging extending from a 1028 mb high centered near 38N158W extends east-southeastward through 27N130W to offshore of SW Mexico near 17N108W. The pressure gradient between the ridge and the monsoon trough to the south is forcing moderate NE trades south of about 25N and west of 130W. Seas are 5 to 6 ft in mixed NE and SE swell south of 25N west of 125W, 5 to 8 ft south of the monsoon trough from 03N to 10N between 90W and 120W, and 4 to 5 ft elsewhere. For the forecast, little overall change is expected over the open Pacific waters W of 120W for the next several days as the aforementioned ridge dominates the region. A weak cold front that is presently crossing 32N126W will sink southward across 30N east of 130W today, then push southeastward before dissipating by Fri morning. This will induce a slight decrease in winds during that time period, with winds then increasing slightly Fri through Sun. SW to W monsoonal winds are expected to become well established this afternoon through the weekend, as the monsoon trough lifts very slowly northward. Moderate to fresh SW to W winds, with small areas of locally strong winds near active thunderstorms, will develop from 05N to 12N and E of 120W Thu night through the weekend. Seas within this wind regime will build to 6 to 9 ft east of 120W during that time. $$ Stripling