671 AXPZ20 KNHC 181558 AAC TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Wed Sep 18 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 1200 UTC surface analysis and satellite imagery through 1545 UTC. ...TROPICAL WAVES... A western Caribbean tropical wave is along 81W/82W and extends southward across Panama and into the eastern Pacific waters north of 05N, moving westward at 10 kt. Scattered moderate to isolated strong convection is within 120 nm either side of the southern part of the wave from 06N to 08N. A tropical wave is 95W extending from the Isthmus of Tehuantepec southward over the eastern Pacific waters to near 04N, moving westward at 10 kt. Scattered moderate to isolated strong convection is within 180 nm west of the wave from 07N to 10N and from 12N to 15N. Similar activity is within 180 nm east of the wave from 10N to 13N. A tropical wave is along 112W from 19N to near 06N, moving westward at 10 to 15 kt. Scattered moderate convection is within 120 nm west of the wave from 12N to 16N. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from northern Colombia to 10N85W to 11N100W to 10N113W to 09N125W to 09N131W, where it transitions to the ITCZ and continues to 09N131W to beyond 10N140W. Scattered moderate to isolated strong convection is within 180 nm of the trough between 97W and 104W, within 180 nm south of the trough between 78W and 84W, and within 120 nm south of the trough between 123W and 129W. Scattered moderate convection is within 120 nm north of the trough between 120W and 123W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A broad surface ridge extends southeastward into the region through 30N129W to offshore of Cabo Corrientes near 17N107W. Over the near and offshore waters of the Baja California peninsula, moderate NW winds prevail, except for strong winds along the coast between Punta Eugenia and Cabo San Lazaro. Seas are 4 to 6 ft in moderate period swell except 6 to 7 ft in the areas of strong winds. Moderate NW to N winds prevail elsewhere to the south across the Revillagigedo Islands, while moderate NW winds are across the near shore waters from Cabo Corrientes to Manzanillo. Light to gentle NW to W winds cover the remaining waters eastward to Tehuantepec. Seas sough of 20N are 4 ft in long period SW swell. Scattered showers and thunderstorms moving westward are over the waters SW of the Gulf of Tehuantepec and Chiapas. This activity is noted from 11N to 15N between 93W and 100W. Light to gentle S to SW winds are over the northern part of the Gulf of California while gentle SW to W winds are over the southern part of the Gulf and light and variable winds are over the central portion. Seas are 1 to 3 ft, except to 4 ft in SW swell across the entrance. For the forecast, the current Pacific ridge will remain in place and fluctuate throughout the week. This pattern will maintain moderate to fresh NW to N winds over the near and offshore waters of the Baja California peninsula today, gradually weakening through Thu. Expect fresh winds near the coast each evening through night. 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 gaps winds N of 30N each evening and night. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gentle to moderate SW to W winds are occurring south of the monsoon trough tonight, along about 10N. North of the monsoon trough, moderate or weaker winds are observed, with moderate easterly gap winds flowing across the Papagayo region. Seas are 4-5 ft in SW swell except to 6 ft south through west of the Galapagos Islands. Increasing scattered to numerous showers and thunderstorms are within 90 nm of the coasts of Panama, Colombia and southern Costa Rica. For the forecast, gentle to moderate SW to W winds will continue south of the monsoon trough near 10N through tomorrow afternoon, then begin to freshen offshore Thu through Sat. Seas will build to 5 to 7 ft during this time in a mix of SW swell and westerly wind swell. Active weather is expected south of 10N Fri into the weekend. North of 10N, 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. Seas will build slightly across the area waters Thu through Sat as a long fetch of westerly winds sets up from offshore to 110W, and generates increasing wind waves moving into the area waters. ...REMAINDER OF THE AREA... Surface ridging extending from a 1030 mb high centered near 38N157W extends east-southeastward to 30N129W to offshore of Cabo Corrientes near 17N107W. The pressure gradient between the ridge and the ITCZ/monsoon trough to the south is forcing moderate to locally fresh NE trades south of 28N and west of 125W, with strongest from 10N to 19N west of 135W. Seas are 6-8 ft in mixed swell south of 17N west of 133W, and 4-6 ft elsewhere. For the forecast, little overall change is expected over the open Pacific waters for the next several days, as the ridge dominates the region. A weak cold front will sink southward across 30N east of 130W Wed night, 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 Sat. SW to W monsoonal winds are expected to become well established south of 10N and east of 120W late Wed through Sat, becoming moderate to fresh. Seas will build to 6 to 8 ft from 03N to 11N east of 120W during that time. $$ Aguirre