454 AXPZ20 KNHC 202154 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Sun Aug 20 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... Tropical Storm Hilary made landfall across Baja California Norte in the past few hours, and is centered near 31.3N 116.1W at 2100 UTC, moving north-northwest at 20 kt. Estimated minimum central pressure is 990 mb. Maximum sustained wind speed is 50 kt with gusts to 60 kt. Seas to 12 ft or greater are found within 150 nm NE, 300 nm SE, 210 nm SW, and 900 nm NW quadrants, with peak seas to 18 ft across the Baja offshore waters and estimated to 22 ft inside the Gulf of California. Scattered moderate convection is occurring north of 31N between 116W and 119.5W. Scattered moderate isolated strong convection is elsewhere across Mexico and the adjacent coasts of Gulf of California north of 24N and east of 113W. Continued weakening is expected through Monday as Hilary races northward through the southwestern U.S. Hilary will move across Southern California late this afternoon through early tonight. In the Southwestern United States, the potentially historic amount of rainfall is expected to cause flash, urban, and arroyo flooding including landslides, mudslides, and debris flows. Dangerous to locally catastrophic flooding impacts are expected through Monday morning. Large swells generated by Hilary will affect portions of the Baja California Peninsula, southern California, and coastal areas inside the Gulf of California through early Tue. This swell will produce very high surf and life-threatening rip current conditions. Please consult products from your local weather office. 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 89W extends southward across Guatemala to the Pacific waters N of 08N. Scattered to numerous convection is described below. A tropical wave is along 105W, north of 03N and moving westward at 15 kt. Scattered convection is described below. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 10N74W to 07N82W to 09N104W, then resumes from 14N116W to 09N131W to 09N140W. Scattered to numerous moderate to strong convection is noted N of 03N E of 93W. Scattered moderate to strong convection is noted from 05N to 13N between 98W and 107W, from 10N to 16N between 112W and 122W, and from 06N to 09.5N W of 125W. ...OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on Tropical Storm Hilary. Strong convection occurring early today near the coasts and along the western slopes of the Sierra Madre Occidentales in Sinaloa and Sonora continues, but has diminished in area coverage. Winds has diminished significantly across the southern Gulf of California and the adjacent Pacific waters. However seas remain 7-10 ft there in southerly swell. Outside of the influence of Hurricane Hilary, isolated showers and thunderstorms are noted in the Mexican offshore waters, but become scattered to the south of 16N across the outer waters offshore of Cabo Corrientes. Farther southeast, moderate NW to N winds generally prevail, with seas 6-8 ft in NW swell. Northerly gap winds has strengthened across the central Gulf of Tehuantepec, where seas are 6-7 ft. For the forecast, winds and seas associated with Hilary will diminish over Mexican offshore waters tonight through Mon as the storm quickly moves north of the area. Strong to near gale force gap winds will pulse across the Gulf of Tehuantepec through Thursday, strongest at night. Looking ahead, another area of low pressure has a low chance of development off southern Mexico through the middle of the week. ...OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Afternoon satellite-derived wind data depicted fresh NE-E gap winds in the Papagayo region. Seas in these waters are 5-6 ft. Moderate or weaker winds and seas of 3-5 ft are prevalent in the rest of the area N of 09N. To the south of 09N moderate to locally fresh W to SW monsoon winds prevail, where seas are 5-7 ft in S and SW swell. Very active thunderstorms prevail across the offshore waters E of 93W. 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... Afternoon 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. $$ Stripling