000 AXPZ20 KNHC 311510 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1525 UTC Mon Jul 31 2017 Tropical Weather Discussion for the eastern Pacific Ocean from the Equator to 32N, east of 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 1500 UTC. ...SPECIAL FEATURES... Tropical Storm Irwin is centered near 21.9N 127.3W at 31/1500 UTC or about 965 nm W of the southern tip of Baja California moving NNW at 12 kt. Estimated minimum central pressure is 1004 mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. Scattered moderate convection is within 60 nm in the SE semicircle. Irwin is expected to maintain a NNW course during the next 24 hours and move over cooler waters, which will diminish convection, and thus lose tropical characteristics. Irwin is expected to become a post-tropical cyclone within 24 hours. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP5/WTPZ25 for more details. ...TROPICAL WAVES... A tropical wave is N of 07N along 90W moving W near 15 kt. Scattered moderate and isolated strong convection is from 05N to 13N between 85W and 95W. Low pressure may slowly develop along the wave during the next few days helping to enhance winds and seas offshore of Central America. A tropical wave is N of 08N along 96W moving W at 10 to 15 kt. Scattered moderate and isolated strong convection is N of 12N between 93W and 98W, including across the Gulf of Tehuantepec. A tropical wave extends is N of 10N along 109W moving slowly. No significant convection remains with this tropical wave and the wave may continue to become ill-defined during the next few days. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 10N83W to 08N90W to 10N110W to 10N115W. The intertropical convergence zone axis extends from 10N115W to 07N131W, with a northern extension from 13N127W to 10N140W. Scattered moderate convection is from 02N to 07N between 78W and 81W, and also from 06N to 09N between 99W and 103W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Northwest winds off the coast of Baja California have begun to freshen overnight as a narrow ridged is building SSE across the area between the remnant circulation of Hilary and Tropical Storm Irwin to the W of the Mexican mainland. These fresh winds have helped to build seas to 8 ft off of Baja California Sur. The ridge will weaken tonight through Tuesday and allow winds to diminish. Generally light to gentle winds will persist elsewhere in the Gulf of California and the offshore Mexican waters south of 20N through mid week. Lingering southerly swell will maintain seas of 5 to 7 ft. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh southwesterly monsoonal flow S of 08N and cross equatorial southerly swell is resulting in combined seas of 7 to 10 ft across the waters. Seas will begin to slowly subside Tuesday through Wednesday. A pair of tropical waves moving across the area this morning are producing very active convection shifting W off of Central America and into the waters E of 90W. These waves are expected to merge by mid-week. Fresh to strong E to SE winds will develop with and behind the second wave across the waters of Guatemala and El Salvador on Tuesday as weak low pressure attempts to develop, building seas to around 8 ft. REMAINDER OF THE AREA... Low pressure, the remnant of Hilary, is near 27N130W at 1009 mb. Fresh to strong winds and seas of 8 to 12 ft are within 150 nm in the N semicircle of the low, with a surrounding area of 8 to 10 ft in mixed swell. The low will dissipate during the next couple of days while continuing to the NW. High pressure located well N of the area extends a narrow ridge axis through 32N124W parallel to the coast of Baja California. The pressure gradient between the high pressure system and the active zone of tropical cyclones will maintain moderate N to NE winds W of 125W through this morning. Long period cross equatorial SSW swell is spreading across the waters S of 08N and E of 110W, producing seas of 7 to 10 ft, and will persist through mid-week. A weak pressure pattern will develop between the remnants of both Hilary and Irwin, and the equatorial trough to the S. This will result in a broadening area of gentle to moderate winds between 10N and 20N, W of 110W through the end of the week. $$ Lewitsky