000 AXPZ20 KNHC 210419 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Mon Aug 21 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 0000 UTC surface analysis and satellite imagery through 0300 UTC. ...SPECIAL FEATURES... Tropical Storm Hilary is centered near the coast of southern California near 33.9N 118.2W at 21/0300 UTC, moving north- northwest at 24 kt. Estimated minimum central pressure is 998 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Rough seas persist off Baja California Norte and the nothern Gulf of California. Convection is now minimal across the area, but across the Southwestern United States, the ongoing and potentially historic amount of rainfall is expected to cause life-threatening to locally catastrophic flash, urban, and arroyo flooding including landslides, mudslides, and debris flows through early Monday morning. Localized flooding impacts, some significant, are also expected across northern portions of the Intermountain West. Large swells generated by Hilary will affect portions of the Baja California Peninsula and southern California through early Monday. These swells are likely to cause life-threatening surf and rip current conditions.through Monday morning. Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml and the latest Hilary NHC Forecast/Advisory and Public Advisory at www.hurricanes.gov for more details. ...TROPICAL WAVES... An Atlantic tropical wave along 90W extends southward across Guatemala to the Pacific waters N of 08N. Scattered to numerous convection is described below. A tropical wave is relocated to around 104W, north of 03N and moving westward at 15 kt. No significant convection is evident near this tropical wave. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N84W to 09N100W to 15N114W to beyond. 08N140W. Scattered moderate convection is noted from 09N to 10N between 84W and 86W, from 12N to 14N between 87W and 89W, and from 07N to 09N between 92W and 94W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on Tropical Storm Hilary. Strong to near-gale force winds are still possible over the far northern portion of the Gulf of California, along with very rough seas, although this will likely diminish rapidly overnight. Seas are still 8 to 11 ft off Baja California Norte, confirmed in part by an earlier altimeter pass. Seas approaching 8 ft are also possible over a large area of the offshore waters of Baja California Sur and through the Revillagigedo Islands. Farther south, fresh to strong gap winds are ongoing across the Gulf of Tehuantepec, due in part to lower pressure over the tropical eastern Pacific. Gentle to moderate winds and moderate seas are noted elsewhere. For the forecast, winds and seas will continue to diminish over the Gulf of California and Baja California. Fresh to locally strong northerly gap winds will continue to pulse strong to near gale force at night across the Gulf of Tehuantepec through Fri. Looking ahead, another area of low pressure may develop off southern Mexico through mid- week. Any tropical development of this system, if any, should be slow to occur while it moves slowly toward the northwest or north- northwest. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Earlier scatterometer satellite data confirmed fresh gap winds across Papagayo. Farther south, fresh SW winds are active south of the monsoon trough, with 4 to 6 ft seas. Slight seas are noted elsewhere. For the forecast, moderate to fresh E winds will pulse at night across the Gulf of Papagayo region through Wed morning. SW monsoonal winds will increase S of 09N between Colombia and waters north of the Galapagos, then increase offshore of Costa Rica and western Panama Mon and Tue. Seas will build to 8 ft Mon and then 8-10 ft on Tue in this area. Active thunderstorms will continue across the area waters Mon and Tue as this occurs. Winds will then diminish late Wed as the monsoon trough lifts northward into Nicaragua and Honduras. ...REMAINDER OF THE AREA... Earlier scatterometer satellite data showed fresh southerly winds south of the monsoon trough between 114W and 131W. Seas in these waters are 6-8 ft. Elsewhere in the basin, a weak pressure pattern prevails W of Hilary, sustaining moderate or weaker anticyclonic winds and moderate seas of 6-9 ft in SE to E swell from Hilary. For the forecast, SW winds will start to increase south of the monsoon trough and east of 120W today and continue through midweek. High pressure will weaken modestly W of 120W through mid-week and bring a return to moderate NE trade winds S of 20N. $$ Christensen