000 AXPZ20 KNHC 301008 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Sun Jul 30 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 Hilary is centered near 23.5N 124.7W at 0900 UTC or about 815 nm W of the southern tip of Baja California, moving WNW at 12 kt. Estimated minimum central pressure is 1003 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Scattered moderate isolated strong convection is within 75 nm across the SE semicircle. Hilary is moving across cooler waters, and associated convection has begun to diminish overnight. As Hilary moves farther NW over the next few days, it will gradually weaken and lose tropical characteristics, likely within the next 24 hours. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP4/WTPZ24 for more details. Tropical Storm Irwin is centered near 17.1N 125.0W at 0900 UTC or about 920 nm WSW of the southern tip of Baja California, moving N at 8 kt. Estimated minimum central pressure is 998 mb. Maximum sustained wind speed is 50 kt with gusts to 60 kt. Scattered moderate to strong convection is within 120 nm across the SE semicircle, while scattered moderate convection is within 75 nm across the NW semicircle. Irwin has strengthened slightly during the past several hours as it remains connected to deep tropical moisture. Irwin is forecast to gradually move more northwestward during the next 48 hours as it follows Hilary out of the tropics, and will also encounter cooler waters as it reaches near 22N Monday. This too will significantly diminish convection and lead to loss of tropical characteristics. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP5/WTPZ25 for more details. ...TROPICAL WAVES... A tropical wave along 90W is moving W at 10 to 15 kt. 17.1N 125. Very active convection has blossomed overnight offshore of Nicaragua and El Salvador ahead of the wave. Scattered to locally numerous moderate to strong convection is observed from 07N to 14N between 87W and 91.5W, while scattered moderate to strong convection is from 05N to 10.5N between 91.5W and 95W. Computer models suggest that this active weather will continue today. A tropical wave is along 103W-104W moving W at 10 to 15 kt. No significant convection is observed. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 10N85W to 12N119W, then continues from 12N128W to 10N140W. No intertropical convergence zone is analyzed E of 140W. No significant convection is observed other than already described in monsoon trough section. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... High pressure centered NW of the area will support gentle to moderate NW winds within 120 nm of the Baja California peninsula through this afternoon. Tropical Cyclone Hilary's affects are mainly west of the area, with some small southerly swell expected to fade across the outer waters beyond 150 nm through this morning. The NW movement of the system will allow a narrow ridge to build between the departing cyclone and Baja California, which will result in moderate to fresh NW winds this evening through Monday night. As these winds increase, seas will build to 7 to 9 ft as these wind waves combine with long period southerly swell moving into the region during the next few days. Cross equatorial long period southerly swell with seas of 7 to 8 ft will reach the offshore waters between the Gulf of Tehuantepec and Cabo Corrientes today, and the waters between Los Cabos and Cabo Corrientes late tonight into early Monday. Elsewhere, generally moderate NW winds and seas of 5 to 7 ft will prevail. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Across the Gulf of Papagayo region, moderate to fresh winds will prevail through the morning hours in the wake of the exiting tropical wave, building maximum seas of 6 to 7 ft in a mix of E wind waves and long period SW swell. Winds will veer more SE and diminish slightly tonight there. On Monday, global models are suggesting a weak area of low pressure to develop in the vicinity of 10N90W and move generally westward through Tuesday and then more W-NW through Wednesday. Likely S-SW monsoonal flow will build seas to 7 to 9 ft across the waters S of Guatemala and the Gulf of Tehuantepec coastline. Elsewhere, gentle to moderate S to SW winds are expected the next few days. Large long period cross-equatorial S-SW swell will continue to propagate into the forecast waters during the weekend, with seas 8 to 9 ft reaching as far north as 10N. The area of 8 ft seas will then reach just offshore all Central America Pacific coastal sections by Sunday. Seas will gradually subside starting Monday. REMAINDER OF THE AREA... A 1028 mb high is located N of the area near 38N135W with a ridge axis extending to just offshore of Baja California Norte. The pressure gradient between the high pressure system and the active zone of tropical cyclones will maintain moderate to fresh N to NE winds W of 120W through Sunday. Long period cross equatorial SW swell of 8 to 9 ft is spreading across the waters S of 10N and E of 110W, and will persist through tonight. As the tropical cyclone activity shifts to the NW and eventually weakens across the northwestern discussion waters, 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. $$ Latto/Stripling