000 AXPZ20 KNHC 271941 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Wed Sep 27 2023 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 1800 UTC surface analysis and satellite imagery through 2000 UTC. ...TROPICAL WAVES... A tropical wave is along 87W north of 05N to across portions of Central America, moving west at around 10 kt. Scattered moderate isolated strong convection is noted from 03N to 12N between 82W and 94W. A tropical wave is analyzed along 129W from 03N to 18N, moving W at 10 to 15 kt. Scattered moderate isolated strong convection is noted from 11N to 16N between 124W and 131W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N80W to 10N98W to 09N106W to 10N118W. Segments of the ITCZ extend from 10N118W to 10N127W, and from 09N132W to 09N139W. Scattered moderate isolated strong convection is noted from 04N to 11N between 119W and 140W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A ridge extends across the offshore waters W of Baja California with a trough extending along the Gulf of California. Moderate NW-N winds are offshore Baja California from near Cabo San Lazaro northward per recent ASCAT scatterometer data, with seas of 7-11 ft in NW swell. A plume of moderate to fresh N-NE winds is in the Gulf of Tehuantepec. Winds are mainly light to gentle elsewhere, along with 4-6 ft seas in typical mixed S and NW swell. In the Gulf of California, seas are 1-3 ft, except 3-4 ft near the entrance. For the forecast, seas of 7-11 ft in NW swell will persist through Thu offshore Baja California before slowly subsiding Fri through Sat. Farther south, moderate to fresh N gap winds will pulse to strong across the Gulf of Tehuantepec at night. Looking ahead, fresh to strong westerly gap winds over the northern Gulf of California will start Fri evening, ahead of a weakening cold front, possibly reaching near-gale force by Sat evening. Winds may increase to moderate to fresh offshore Baja California Sur early next week as high pressure builds in behind the front. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... A tropical wave is moving just W of the Papagayo region as described above. Light and variable breezes are evident off northern Central America, N of the monsoon trough, along with combined seas of 3-5 ft in southerly swell. Gentle to moderate southerly winds are noted S of the monsoon trough per recent ASCAT scatterometer data. Combined seas are 4-7 ft there, except 5-8 ft offshore Ecuador, highest S of the Galapagos Islands. For the forecast, gentle to moderate winds will prevail to the north of 05N with seas 5 ft or less through Sun night, with moderate SW winds farther south. Seas may build slightly in southerly swell early next week. Seas south of 05N will build to 6-9 ft in southerly swell through Fri evening, with seas highest to the SW of the Galapagos. ...REMAINDER OF THE AREA... A tropical wave described above along 129W combined with high pressure N of the monsoon trough/ITCZ is supporting a growing area of fresh to strong winds roughly from 12N to 23N between 124W and 140W as confirmed by recent ASCAT scatterometer data. Moderate to fresh trades cover the remainder of the waters N of the monsoon trough/ITCZ and W of 117W. A large area of northerly swell of 7-11 ft roughly N of 13N and W of 114W, up to around 12 ft N of 25N between 119W and 130W per earlier altimeter data. To the south, mainly moderate southerly winds are S of the monsoon trough/ITCZ. Southerly swell of 7-10 are S of 05N and W of 110W. Mainly gentle winds and 4-7 ft seas cover the remainder of the open waters. For the forecast, the tropical wave will continue westward, approaching 140W Fri morning. Some development of this system is possible over the next couple of days while it moves generally westward at about 10 to 15 kt. By this weekend, upper-level winds are forecast to become unfavorable for further development before the system moves into the Central Pacific basin. At a minimum, fresh to strong seas and seas of 8-13 ft will accompany this feature. High pressure will dominate the waters elsewhere N of the monsoon trough/ITCZ. The pressure gradient will weaken by the end of the week into the weekend as the tropical wave departs and the high weakens leading to improving conditions. Meanwhile, for seas, the northerly swell of 8 ft or greater will reach to the Equator and W of 115W by the end of the week, while the southerly swell of 8 ft or greater lingers near the Equator and southward. Both large areas of swell should gradually decay this weekend. $$ Lewitsky