000 AXPZ20 KNHC 010924 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Tue Aug 1 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 0600 UTC surface analysis and satellite imagery through 0830 UTC. ...SPECIAL FEATURES... Tropical Storm Irwin is centered near 24.9N 128.8W at 0900 UTC or about 1040 nm W of the southern tip of Baja California, moving NNW at 11 kt. Estimated minimum central pressure is 1007 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Scattered moderate convection is occurring within 120 nm across the NE quadrant. Irwin is expected to maintain a NNW course during the next 24 hours and move over cooler waters. This will cause Irwin to lose convection and continue to weaken. Irwin is expected to become a post-tropical cyclone with 25 kt winds at within 24 hours. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP5/WTPZ25 for more details. ...TROPICAL WAVES... A tropical wave along 92W-93W continues to produce a broad area of active convection. Recent scatterometer data showed a weak surface low near the wave axis, now estimated at 1009 mb near 10N92.5W, moving W around 15 kt. Widely scattered to scattered moderate to strong convection is spread across the region from 06N to 10N between 85W and 94W, and from 10N to the coast between 85W and 101W. Some of this weather is also associated with a tropical wave just a few degrees ahead of this wave, described below. As the wave shifts westward during the next 48 hours, look for E to SE winds of 20-25 kt to prevail within 270 nm NE of the surface low, where seas will build 8 to 9 ft. A tropical wave is along 97W-98W moving W 10-15 kt. Convection associated with this wave is occurring across the waters of Mexico between Puerto Angel and the Acapulco area, and is described above. Associated weather is expected to shift W and NW along the coastal waters of Mexico during the next few days. A tropical wave is along about 100W and has temporarily moved into a region of weak low level troffing extending S from the southern tip of Baja California. Convection is limited at this time. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N74W to low pres 1009 mb near 10.5N94W TO 10N110W TO 07N125W. The ITCZ continues from 07N125W TO 10N140W. Widely scattered moderate and isolated strong convection is found within 180 nm S and 75 nm N of the trough between 102W and 125W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... The narrow ridge extending SSE across the area between the remnant circulation of Hilary and Tropical Storm Irwin and the Baja Peninsula has weakened slightly overnight and is drifting westward. This has allowed NNW winds along the Baja waters to diminish slightly since sunset, with this trend expected to continues today. Generally light to gentle winds will persist elsewhere over the Gulf of California and the offshore Mexican waters south of 20N through mid week. Otherwise, moderate long period S swell from the Southern Hemisphere will maintain offshroe seas of 5 to 7 ft, and continue to generate large surf along the coasts. Slowly developing low pressure associated with westward moving tropical waves is expected to bring fresh to strong winds and seas building above 8 ft to the waters between the Gulf of Tehuantepec and Cabo Corrientes Wed through Fri. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh SW monsoonal flow S of 08N and cross- equatorial southerly swell are combining to produce combined seas of 7 to 9 ft across the waters. Seas will begin to slowly subside Tuesday through Wednesday as the S swell gradually decays. A pair of tropical waves described above between 92W and 102W are producing active convection along the coast of Central America from Costa Rica to Acapulco, Mexico. These tropical waves are expected to continue moving W through Wednesday and spread this active weather with them. Fresh to strong E to SE winds will develop along and behind the easternmost wave across the waters of Guatemala and El Salvador today as low pressure along the wave continues to slowly develop. REMAINDER OF THE AREA... Low pressure, the remnant of Hilary, is centered near 28N133W at 1012 mb. Fresh winds and seas of 8 to 10 ft are occurring within 210 nm across the NE semicircle of the low. The low will dissipate during the next couple of days as it continues to the NW. High pressure centered off the NW Coast of the United States extends a narrow ridge through 32N126W parallel to the coast of Baja California to near 15N122W. The pressure gradient between the high pressure system and the area of low pressure associated with Hilary and Irwin will maintain moderate N to NE winds N of 20N and W of 130W tonight. Long period cross equatorial SSW swell continues arriving across the waters S of 08N and E of 110W. The swell will produce seas of 7 to 9 ft, which will persist until the swell decays around mid week. A weak pressure pattern will persist between the remnants of 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 120W through the end of the week. $$ Stripling