Eastern Pacific Hurricane Hilary made landfall on the Baja Peninsula early on the morning of the 20th and reached Southern California as a tropical storm that afternoon. The cyclone brought widespread flash flooding to southeast California, along with isolated high winds.
Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS VEF wrote it up.
Eastern Pacific Hurricane Hilary made landfall on the Baja Peninsula early on the morning of the 20th and reached Southern California as a tropical storm that afternoon. The cyclone brought widespread flash flooding to southeast California, along with isolated high winds.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Las Vegas, NV wrote its last area forecast discussion before the first event at Aug 19, 2:22 AM PST, 9 hours 40 minutes earlier.
Area Forecast Discussion National Weather Service Las Vegas NV 322 AM PDT Sat Aug 19 2023 .SYNOPSIS...Rich moisture related to approaching Tropical Cyclone Hilary will begin to advance into the Mojave Desert today with increasing shower and thunderstorm activity expected. This trend will continue into Sunday as the remnants of Hilary lift northward. Widespread heavy rain, gusty winds, and instances of major flooding are expected. Hilary's remains will exit the region by Monday but moist monsoonal conditions will persist much of the week with daily storm chances and temperatures remaining below normal. && .SHORT TERM...through Monday. Still on track for a rare and highly impactful weather event unfolding this weekend across the southwestern US as the remains of what is currently Hurricane Hilary lift through Southern California and the Mojave Desert. The details of the forecast are largely unchanged, and model guidance remains in very tight agreement on the track of Hilary's remnant circulation and the general swath of heaviest precipitation. While Hilary is currently a category 4 hurricane roughly 260 miles west of Cabo San Lucas, she will weaken quickly on approach of the northern Baja and will either be a weakening tropical storm or depression by the time she reaches the US border and into our deserts. Nonetheless, a tremendous amount of tropical moisture will funnel into the region from the Gulf of California, aided by a very strong southeasterly mid and low flow which will begin to ramp up today. Best chance for excessive rainfall and flash flooding today will be focused in western San Bernardino County as well as Inyo County, though the flash flood risk exists everywhere. Integrated Water Vapor transport ahead of Hilary ramps up dramatically tonight and blasts up the Colorado River Valley, with widespread precipitation breaking out and increasingly heavy rainfall rates likely. The WPC has continued a High Risk for excessive Rainfall across much of Inyo and San Bernardino Counties Sunday, which is where the greatest threat for catastrophic and damaging flash flooding exists. We are especially concerned for historical rainfall occuring in Death Valley National Park which will greatly challenge regional infrastructure. By Monday morning, a swath of 2-5+ inch rainfall totals are expected across the western Mojave Desert, which could result in catastrophic flooding in Death Valley, the Morongo Basin and Barstow areas. Areas of orographic enhancement such as the Panamint Range, Spring Mountains, and southern Sierra could squeeze out event higher rainfall totals exceeding 5-7+ inches. Further east, across the eastern portions of the Mojave Desert including the Mojave Preserve and Las Vegas Valley, significant rainfall is likely in these areas as well, though the heaviest precipitation is currently favored in the aforementioned western zones closer to Hilary's remnant circulation. Nonetheless, southeasterly upslope flow over the McCullough Range and Spring Mountains will aid in heavy precipitation generation which could result in significant precipitation accumulations and flash flooding. Additionally, with precipitable water values climbing to near 2" or more from Las Vegas south, even brief rain showers can produce extremely intense rainfall rates causing rapid flash flooding. The driest part of our forecast area will be Mohave County but the very moisture rich airmass will still support very efficient rainfall with shower and thunderstorm activity that occurs, and locally impressive rainfall totals will be possible here as well, especially near the Hualapai Mountain range. In addition to the rain threat, as Hilary's remnant circulation lifts through southern California, strong winds may spread northward out of the Sonoran Desert and into the Mojave Sunday afternoon and evening, spreading into the Southern Great Basin by Monday. There is uncertainty in how strong these winds will be and they will be dependent on how quickly Hilary weakens in the next 48 hours, but wind advisories or even a short fused high wind warning may be needed for areas along the Colorado River and south of I-40 for Sunday evening. With additional advisories possible Sunday night into Monday for areas further north. Whats left of Hilary, which will become unrecognizable by this time, will lift into the Great Basin Monday. Rich tropical air will remain in place with a rather strong southerly flow continuing, which will tend to favor the higher terrain of southern Nevada for heavy rainfall Monday, with drier and more stable air tending to work in further south. Temperatures through the short term period will be well below normal thanks to the abundance of clouds and moisture, with high temperatures Sunday likely to challenge record daily low maximum temperatures for many areas. .LONG TERM...Tuesday through Friday. Following the exit of what is left of Hilary on Monday, widespread low level moisture will remain in place. Synoptically, an expansive ridge will remain parked over the central US with a southerly flow featured across the southwestern states. This will result in at least low-grade monsoonal conditions persisting most of next week, with daily storm chances favored in the higher terrain, but possibly drifting into the lower elevations in the afternoon and evening hours. Subtle shortwave features embedded in the flow may also result in some days being more active than others and promote more lower elevation activity. For now, NBM PoPs keep fairly generous storm chances going through the week across Northwest Arizona and southern Nevada, with slight chances across most of southeast California. With the abundance of moisture and continued daily storm activity, temperatures remain cooler than average by 5-10 degrees, but should trend warmer heading into the end of the week. && .AVIATION...For Harry Reid...Light and variable winds early this morning will turn southeast by late morning. Prevailing winds should remain less than 10kts, but scattered thunderstorms are possible after 20Z, and any that do develop will be capable of producing gusty, erratic winds. More steady light to, at times, moderate rain is expected after 04Z as moisture from Hilary spreads across the area. In addition to the rainfall, reduced visibilities of 5mi or less and CIGs less than 4kft are also expected by daybreak Sunday. The rain and reduced CIGs and visibilities will likely continue into Sunday evening. For the rest of southern Nevada, northwest Arizona and southeast California...Scattered thunderstorms are expected across the region once again today. The best chance is after 20Z, and any storms that do develop will be capable of producing gusty, erratic winds. Away from thunderstorm activity, winds of less the 10kts generally from the east and southeast can be expected. Moisture from Hilary will begin to spread across the area this evening into tonight, resulting in steady rain developing from south to north. In addition to the moderate to, at times, heavy precipitation, reduced visibilities down to 2 to 4 SM at times and CIGs less than 2kft will be possible, with the degraded conditions continuing into Sunday night. && .SPOTTER INFORMATION STATEMENT...Heavy rain, high winds, and flash flooding reports are requested through the weekend as the remains of Hurricane Hilary lift through the Western Mojave Desert. && DISCUSSION...Outler AVIATION...Planz For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter
The Edwards AFB radar (KEYX), 140 km away, was scanning. The volume nearest the first event began at 20:00 UTC.
23 flash flood, 3 high wind, 2 flood, 1 lightning. Local standard time, as filed.
Water and debris flooded Highway 190 between mile markers 45 and 46.
The intersection of Highways 190 and 136 was washed out. The road remained closed and intermittently flooded for over a day.
Highway 395 flooded both in Lone Pine and at Boulder Creek 4 miles SSE of Lone Pine.
Rocks and debris blocked Highway 190 at Towne Pass.
A large pool of standing water covered the intersection of Highways 190 and 127 for several hours.
Major flash flooding occurred throughout Death Valley National Park. Four hundred miles of NPS roads were damaged or destroyed, in addition to other roads maintained by the county and state. About 1000 feet of fresh water lines were destroyed at Furnace Creek. Damage to most structures was minimized or prevented by berms and other protections. The exact start and end times are unknown.
Lightning struck a utility pole next to I-15, closing the highway for a period.
Flash flooding occurred throughout the Mojave National Preserve. All roads, facilities, trails, etc in the preserve were closed. Exact start and end times unknown.
Heavy flooding pushed debris across Highway 62 between Cactus Jack and Godwin.
These winds occurred 10 miles SSE of Essex.
Mud and debris washed onto Highway 62 just east of Olympic Rd.
Several roads in Twentynine Palms were closed due to flooding.
A boulder washed onto Highway 62 at Hess Rd.
Flash flooding in Baker was up to vehicle hoods.
Highway 95 was flooded near mile marker 17.
The intersection of Highway 178 and Trona Rd was flooded with multiple vehicles stuck, and 178 was also possibly washed out at Pinnacle Rd.
Water and mud covered La Contenta and Alta Loma Rds.
Four feet of rushing water trapped people in their cars on Highway 127. The road was severely damaged.
Mud and debris covered the intersection of Amboy Rd and Cactus Jack.
A slide of mud and gravel covered Highway 395 at Ash Creek Rd. Mud flowed heavily along the side of the highway and into part of the southbound lanes. Due to ongoing flooding in multiple places, Highway 395 was eventually closed all the way from Bishop to Pearsonville overnight.
The intersection of Highway 395 and Randsburg Cutoff Rd was flooded.
Fast-moving water covered the intersection of I-15 and Fort Irwin Rd.
This gust blew part of the roof off of a house 2 miles WSW of Twentynine Palms.
Highway 247 was flooded and closed at Pipes Canyon Rd.
Fast flowing water, rock, and debris covered Whitney Portal Rd, the Whitney Portal parking lots, and the road to Lone Pine Campground. Whitney Portal Rd was destroyed by high flows in Lone Pine Creek.
A vehicle was covered in mud and sinking at the intersection of Covington Dr and East Dr.
Two feet of rock and debris covered Highway 62 near Valley View Rd, and small boulders were on the highway from Senilis Ave to east of Valley View Rd.
The Amargosa River flooded Old Spanish Trail Crossing in Tecopa for several hours.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2023Every state in 2023This day in weather historyWarnings in California, August 2023
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1137032, 1137041, 1137043, 1137044, 1137045, 1137047, 1137048, 1137055, 1137060, 1137061, 1137069, 1137073, 1137074, 1137075, 1137076, 1137077, 1137079, 1137081, 1137082, 1137083, 1137084, 1137085, 1138484, 1138485, 1138491, 1138494, 1138492, 1138493, 1138497.