000 AXPZ20 KNHC 310731 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Thu Aug 31 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 0600 UTC surface analysis and satellite imagery through 0650 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from Panama near 09N78W to 11N98W to 07N126W. The ITCZ is W of 140W. Scattered moderate convection is evident from 02N to 06N between 92W and 98W, and within 180 nm S of the monsoon trough between 100W and 124W. Similar convection is from 02N to 09N within 75 nm of the coast of Colombia, and from 20N to 26N between Mexico and 110W, including the entrance to the Gulf of California. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Broad surface troughing extends from near Punta Eugenia to 1007 mb low pressure near 20N115W as sampled by a recent ASCAT scatterometer pass. Gentle to moderate winds dominate the offshore waters of Mexico, except in the Gulf of California where moderate to fresh winds are occurring mainly due to nearby convection. Seas are 4-6 ft in mainly long period S-SW swell from Cabo San Lazaro southward, and 5-8 ft in NW swell from Cabo San Lazaro northward. Seas are 2-4 ft in the Gulf of California. For the forecast, nightly surges of fresh to strong winds are forecast in mainly the northern portion of the Gulf of California due to convection developing over mainland Mexico through Fri night. Fresh to strong northerly winds will pulse in the Gulf of Tehuantepec late Fri night through Sat night. Winds will be moderate or weaker elsewhere through Sat. Winds will increase to moderate to fresh nearshore Baja California Sun night as the pressure gradient tightens along the peninsula. Meanwhile NW swell of around 8 ft offshore Baja California Norte will subside today, with seas possibly building back to around 8 offshore all of Baja California early next week. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle winds prevail across the offshore waters N of 05N along with seas of 4-5 ft, except 4-6 ft offshore Panama and Colombia in long-period south to southwest swell. To the south of 05N, including the waters offshore southern Colombia and in between Ecuador and the Galapagos Islands, moderate to locally fresh S winds with seas of 7-9 ft are present due to long-period S to SW swell. Scattered tstms are noted along the coast of Colombia ahead of a tropical wave currently over the S-central Caribbean Sea and central Colombia. For the forecast, moderate to locally fresh south to southwest winds will continue between the coast of Ecuador and the Galapagos Islands most of the time through the weekend. Southerly swell will keep seas around 7-9 ft there through today before subsiding slightly, then renewed long period S to SW swell will move through those waters Fri, increasing seas back to 7-9 ft through Sat through the weekend. Swell of 6-8 ft will reach the waters offshore Panama and Costa Rica. Elsewhere, light to gentle variable winds will prevail through most of the the forecast, locally and occasionally moderate to fresh near Gulfs, along with slight to moderate seas in long-period SW swell. ...REMAINDER OF THE AREA... The post-tropical remnant low of former Tropical Cyclone Irwin is centered near 20N136.5W with an estimated central pressure of 1011 mb. It is moving westward at around 10 kt. A tight pressure gradient between the low and strong high pressure to its north is keeping strong to near gale force winds in the northwest semicircle from the low to 28N between 132W and 140W. Seas are 8-13 ft N of 14N and W of 132W. Scattered moderate convection is present within 75 nm in the N semicircle. Elsewhere north of 22N and west of 120W, fresh N to NE winds and 7-10 ft seas prevail, with locally strong winds N of 28N. Winds are mainly moderate or weaker across the remainder of the open waters. Seas of 5-8 ft prevail across the remainder of the waters N of 05N, and 6-9 ft seas in southerly swell S of 05N. For the forecast, the post-tropical remnant low of Irwin will continue moving westward, with a slightly slower motion expected, reaching 140W Fri afternoon. Fresh to strong winds and elevated seas will continue to accompany the low, mainly in the NW semicircle. Elsewhere, northerly swell will propagate through the open waters well W of Baja California through early Fri, keeping seas of 6-10 ft N of 20N and W of 120W. Southerly swell in the far southern waters to the south of 06N will keep seas 7-10 ft through today before subsiding slightly. Another long period S swell event will push northward across the Equator tonight and Fri with seas of 8-9 ft south of 05N and east of 120W into Sat before subsiding late in the weekend. A broad north-south oriented surface trough with accompanying low pressure is expected to move from along 112W to 120W by the weekend, resulting in shifting winds. $$ Lewitsky