The 2022-2023 water year in Eaton Canyon has ended as one of the most impressive water years of the past century. A copious number of storm systems well spread out throughout the entire season dumped a grand total of 4-5 feet of rain. In the past 116 years, only 2005 was able to drop more rain in Eaton Canyon. Included in this astounding year was well over 10 feet of snow on the highest peaks of Eaton Canyon, a landfalling tropical cyclone interrupting a hot summer, and absolutely no destructive flash flooding of any kind throughout all 12 months. Following the driest water year on record in 2021, in which Eaton Dam picked up only 5.63″, as well as the single longest, hottest, most extreme summer ever in 2022, the biological features of Eaton Canyon were suffering greatly. After 23 years of megadrought conditions across the western United States, this is precisely what Eaton Canyon needed to recover.Â
Contrary to popular belief, megadroughts can not be ended in a single year even if record amounts of precipitation falls. Megadroughts are defined as ecologically destructive events in their own right, as they can cause entire species to go extinct, ecosystems to collapse, and ecological biomes to shift dramatically. While short-term extreme droughts can be sudden, megadroughts are relentless and span decades. Megadroughts can actually allow for native species to respond to changing climates. A minimum of 3 consecutive wet winters and cooler than average summers are needed to repair those damaged ecosystems and food chains. Some areas may require 5 such years to fully recover. This isn’t about reservoir levels or how good of a ski season it was, this is about the health of the entire ecosystem of this region of the world. In this era of rapid climate change, such a period of relief is less and less likely. Most summers in the 21st century are oppressive and lengthy. Even 2023 was an extremely hot summer for Southern California, with the July-August period being the second hottest July-August period ever behind only 2022. That being said, the canyon was struck by a landfalling tropical cyclone in mid-August that dumped 5″ – 7″ of drought-relieving rainfall. These tropical downpours kept the gains of the previous winter alive. More on Tropical Storm Hilary’s impact on Eaton Canyon can be found here.Â
Timeline of the 2022-2023 Eaton Canyon Water Year:
October 2022
Following a horrid summer that included our longest, most intense heat wave ever recorded in this area, October 2022 brought 0.3″ of rain to the canyon during a convective storm. Forecasts issued by long range meteorologists and climatologists called for a drier than average winter 2023 in California. This was not good news as the state was mired in both a 23-year megadrought and a 2-year long intense episode of exceptional drought.
November 2022
Moderately strong rainstorms began arriving in California in November, with the area picking up a healthy 3.29″. Signs that a wet winter ahead in California became more clear, and long-range forecasts for December-February were tuned.
December 2022
Occasional downpours continued into December, with another 4.97″ falling in the canyon. Drought impacts began to become mitigated, and the canyon responded with new growth.
January 2023
On New Year’s Day, the subtropical jet stream over the West Pacific became extremely powerful. When this happens, regions of Earth downstream can see rapidly changing weather daily for weeks on end, with troughs of low pressure and ridges of high pressure moving by quickly without ever stopping. Think of water shooting out of a hose that becomes wavy and rippled as it travels further away.
As a result of this powerful jet, a series of intense North Pacific storms began slamming into California at the start of the calendar year, dropping significant amounts of rainfall. Any time a ridge of high pressure tried to form, it immediately got knocked over by the next storm in line. Well over a foot of rain came down in Eaton Canyon in the first two weeks, totaling 13.45″. The strongest storm occurred on January 10th when 5.42″ fell in a single day. Several feet of snow fell in the upper canyon, reducing flash flood risk. Destructive flash flooding was fairly non-existent as most of the precipitation fell as snow.
Around the 15th, the clouds began to part. For the next 4 weeks, sunshine would prevail as the storm track retreated into Northern California. One system late in the month did produce 3/4ths of an inch, however. At this point, if the rainy season were over, we would land with one of the wettest winters of the 21st century.
February 2023
The first 3 weeks of February 2023 were relatively calm and sunny, allowing vegetation to really grow throughout the canyon. Western Sycamores thought winter was over, and began sprouting leaves. Some of the oldest Western Sycamores in the canyon knew what was up, however, and did not partake in the springtime festivities.
The lull ended around the 21st when a series of extremely cold, wet systems again swept the state. Heavy snowfall came down throughout the entire canyon, accumulating just a couple hundred feet above Eaton Wash. Snow fell across several low elevation Southern California communities. Torrential rain that lasted for days brought another 8.77″ to the canyon. Those Western Sycamores trees that had decided to leaf out in early February postponed spring and let all of their new foliage die in a second autumn. Since most trees were weeks into their spring growth, this was damaging to them.
March 2023
March arrived with chilly weather and yet more heavy rain evenly spread out throughout the month. Rain was observed on nearly half of all days in March, with little sunshine or warmth. 9.30″ fell in the canyon during the month, which is actually quite incredible for March.
April 2023
The storm series finally slowed in April, with only half an inch of rain being reported. Sunny skies and warm temperatures following a wet, cold winter allowed for considerable spring growth throughout the canyon.
May 2023
A handful of late season storms soaked the canyon yet again in early May, totalling another 2.09″. This rain helped keep vegetation growth strong during late spring.
June 2023
Not much rain fell in June, but extreme cloudiness prevailed across coastal Southern California, including at Eaton Canyon. While the upper portions of the canyon enjoyed cool, sunny, breezy skies, the lower 3/4ths of the canyon was mired in fog all month long. Much of this fog helped conifer trees create their own rain under their canopy, and as much as a few additional inches of rain fell in these parts of the canyon.
July 2023
The canyon got only a trace of rain in July, allowing the canyon to dry out and enjoy some sunshine. The area got very unlucky when remnants of Hurricane Eugene bypassed Los Angeles County on either side, missing the canyon but dropping up to 1.00″ to both the east and west.
August 2023
Very little rain is ever expected in August as the monsoon flow typically does not favor the south face of the San Gabriels. However, that all changed when a large complex of thunderstorms several hundred miles south of Acapulco, Mexico detonated into a juggernaut category 4 hurricane with an impressive 700 mile wide cloud field. The large hurricane, named Hilary, began racing directly for Southern California carrying huge amounts of tropical moisture. After juking out meteorologists who thought the system was headed inland through Baja California, Tropical Storm Hilary suddenly deviated to the left nearly one hundred miles and made landfall in Los Angeles County, California as a bonafide tropical storm, dumping over half a foot of rainfall on Eaton Canyon in a single day. The center passed over downtown and headed through La Crescenta into the Angeles National Forest, putting Eaton Canyon in the right eyewall. Fears of excessive rain rates did not come to fruition, but gusty winds and 24 hours of steady tropical downpours accompanied the tropical cyclone. Rare tropical convection was seen building over the canyon the day prior. This was Eaton Canyon’s second encounter with a landfalling tropical cyclone on record, as the 1938 Long Beach Tropical Storm also passed directly overhead.
September 2023
September is also usually hot and dry, but a series of marine layer events early in the month brought light rain to the canyon. Late in the month, a pair of thunderstorms moved over the canyon when a very early season winter storm impacted Southern California. 0.30″ of rain was reported.
Thank you Edgar for the informative report.