000 AXPZ20 KNHC 310949 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 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 0600 UTC surface analysis and satellite imagery through 0830 UTC. ...SPECIAL FEATURES... Tropical Storm Irwin is centered near 20.7N 126.7W at 0900 UTC or about 950 nm WSW of the southern tip of Baja California moving NNW at 11 kt. Estimated minimum central pressure is 1002 mb. Maximum sustained wind speed is 50 kt with gusts to 60 kt. Scattered moderate and isolated strong convection is within 75 nm SE and 60 nm NW semicircles of the center. 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. Post-Tropical Cyclone Hilary is centered near 26N129W at 600 UTC or about 1020 nm WNW of the southern tip of Baja California moving NW at 12 kt. Estimated minimum central pressure is 1008 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. Satellite imagery shows shallow convection occurring within 180 nm across the NE semicircle. Hilary is expected to move NW to WNW during the next 24 hours and then gradually become absorbed within the weakening circulation of Irwin at around 48 hours. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP4/WTPZ24 for more details. ...TROPICAL WAVES... A tropical wave is along 87W-88W moving W near 15 kt. Scattered to numerous convection has shifted across Central America overnight and is now from 03.5N to 14N between 82W and 96.5W. A tropical wave is along 94W-95W moving W at 10 to 15 kt. A few clusters of scattered moderate to strong convection are observed from 08N to 16.5N between 93.5W and 97.5W. A tropical wave extends is along 106W-107W moving W at 10 to 15 kt. Isolated moderate convection is near the Mexican coast from near Acapulco to Mazatlan. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from low pres near 11N81.5W 1012 MB TO 08N90W TO 11N112W. The ITCZ extends from 13.5N128W TO beyond 10.5N140W. Scattered moderate to strong convection is noted from 03.5N to 08N E of 79W. ...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 twins of Hilary and Irwin to the W and the Mexican mainland. Winds are expected to build to near 20 kt across most of the area with isolated spots to 25 kt. This will build seas to 6-8 ft across the area in mixed NW wind waves and long period southerly swell. The ridge will weaken tonight through Tue 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 the peak of a new pulse of southerly swell will build seas to 7 to 9 ft across the waters today, before beginning to slowly subside Tue through Wed. 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 this morning. These wave will shift W over the next few days and maintain active weather, and are expected to merge SSW of Tehuatepec Tue, where broad low pressure will develop. Fresh to strong E to SE winds will develop with and behind the second wave and brush along the coast and coastal waters of Guatemala and El Salvador on Tue, raising seas to around 8 ft. REMAINDER OF THE AREA... A 1028 mb high is located well N of the area near 41N134W with a narrow ridge axis extending SSE and parallel 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 127W through this morning. Long period cross equatorial SSW swell is spreading across the waters S of 10N and E of 110W, producing seas 8-9 ft, and will persist through midweek. As the weakening tropical cyclones shifts to the NW and become non tropical, a weak pressure pattern will develop between the remnant cyclones and the equatorial trough to the south. This will result in a broadening area of gentle to moderate winds between 10N and 20N, W of 110W early next week. $$ Stripling