From Saturday afternoon’s rain-free run to check out upper Las Virgenes Creek. The nearby Cheeseboro Remote Automated Weather Station (RAWS) had recorded about 2.0 inches of rain the previous three days and would record another 2.4 inches on the following two. The weather station is on top of the prominent hill in the distance. January was the wettest at Downtown Los Angeles (USC) since January 2005.
The oval disturbance in the layer of altocumulus clouds in this photograph is a relatively rare phenomenon called a fallstreak hole or hole punch cloud.
These altocumulus clouds are formed from super-cooled water droplets many times smaller than a raindrop. The droplets are in a liquid state even though the temperature is well below freezing. When disturbed by an aircraft passing through the layer the droplets freeze and precipitate out of the cloud as virga. This and other processes create the hole.
The photo was taken on Saturday, January 21, 2017 at 2:23 p.m. near the Las Virgenes trailhead of Upper Las Virgenes Canyon Open Space Preserve. The hole was well south of the area.
With a storm approaching and rain only an hour or two away, I’d been debating where to turn around. I’d just climbed the steep hill between Upper Las Virgenes Canyon and Cheeseboro Ridge and decided to continue down to Cheeseboro Canyon. As I drew closer to the trail’s junction with Cheeseboro Canyon, I began to hear a cacophony of cawing crows.
At the junction crows literally filled the sky (video). It seemed the call was out and crows were coming from all directions to join the flock.
Though I’d never seen such a large aggregation in Cheeseboro Canyon, it is common for the American crows (Corvus brachyrhynchos) to form large foraging and roosting flocks in winter. Winter is tough on animals and isn’t surprising that the social and intelligent crow would cope with Winter in this cooperative fashion.
Leaving the crows behind I started the trip back to the Victory trailhead. It would take about an hour and I hoped the rain didn’t get there before I did!
As of yesterday Downtown Los Angeles (USC) has recorded 8.80 inches of rainfall for both the Rainfall Year (July 1 – June 30) and Water Year (October 1 – September 30). By either measure Los Angeles rainfall is well above normal, and with three well-advertised storms in the forecast it looks like Los Angeles rainfall could remain above normal for at least a few weeks.
Even if it has been a bit wet — and muddy — it’s been great to have a more normal rain season. The rain has been very beneficial and has impacted the drought, at least in the short term. Just how much a continued wet rain season would impact the drought in the long term is a question that has to wait for future analysis.
There has been a five year precipitation deficit of nearly 36 inches at Downtown Los Angeles (USC). It’s hard to appreciate the size of this deficit while running in the rain, splashing through puddles, and trying not to slip in the mud. One tangible indicator of this deficit is that despite above average rainfall, many creeks in the Santa Monica Mountains and Simi Hills have remained dry or are barely flowing. Some have been dry for years.
Update Wednesday, March 1, 2017. The atmospheric river event on February 17 produced high flows on many local streams and many of these streams continue to flow. Rainfall totals in Los Angeles, Ventura and Santa Barbara Counties for the storm generally ranged from 4 to 8 inches with some higher totals recorded. On subsequent trail runs flooding, debris flows and erosion were noted in Upper Sycamore and Blue Canyons in Pt. Mugu State Park. Remarkably, some groundwater monitoring stations in Santa Barbara and San Bernardino Counties remain well below normal.
As of February 28, 2017, Downtown Los Angeles (USC) had recorded 18.50 inches of rain for the Rain Year and Water Year. This is 165% of the normal amount of 11.24 inches for the date, and 124% of the normal amount of rainfall for an entire year. This is the wettest Rain Year (July 1 – June 30) and Water Year (October 1 to September 30) to date since the very wet year of 2004-2005.
Update Tuesday, January 24, 2017. From Wednesday, January 18 through Monday, January 23, Downtown Los Angeles (USC) recorded 5.53 inches of rain, bringing the Rain Year and Water Year precipitation totals to 14.33 inches. This is 217% of the normal amount of 6.65 inches for the date, and 97% of the normal amount of rainfall for the entire Rain Year. It has been the wettest start to the Rain Year (July 1 – June 30) and Water Year (October 1 to September 30) since the very wet year of 2004-2005. There were high rain rates on Sunday, January 22, and Upper Las Virgenes Creek did finally flow for a period of time.
Update Saturday, January 21, 2017. From Wednesday, January 18 through Friday, January 20, Downtown Los Angeles (USC) recorded 2.53 inches of rain, bringing the Rain Year and Water Year precipitation totals to 11.33 inches. The average annual rainfall for Downtown Los Angeles is 14.93 inches. The rain, which was heavy at times on Friday, produced some flooding, rockslides and debris flows. Both branches of upper Garapito Creek are flowing as a result, but Saturday afternoon Upper Las Virgenes Creek was still not flowing.
Upper Las Virgenes Creek – February 22 the flow on Upper Las Virgenes Creek near the Cheeseboro connector and the two downstream crossings was enough that you couldn’t cross without getting your shoes wet. Previously, on January 24, there was no flow near the connector and only a slight trickle downstream. On January 21 the creek was not flowing and there was no evidence it had flowed during a recent storm.
Garapito Creek – On Saturday, January 21, 2017, both branches of upper Garapito Creek were nice burbling brooks. Previously, on January 15, the north branch was just starting to flow, but the south branch was dry.
Upper Sycamore Creek – Flash flooding, debris flows and erosion occurred on this creek following the heavy rain on February 17-18. Nearly 6 inches of rain was recorded at Circle X Ranch, which is also in the western Santa Monica Mountains. Previously, was flowing on February 4, but not on January 1, 2017.
Serrano Creek – Was flowing on February 4, but not on January 1, 2017.
If the wet forecast holds will these streams start to flow? We’ll see!
As I climbed the long hill, the wind began to increase, gusting fitfully in one direction and then another. Chilled, I stopped to pull on my sleeves. As I tugged at one sleeve the setting sun suddenly broke under the patchwork of clouds, illuminating the hills in a wonderful — but fleeting — golden light.
Such situations can be anticipated, but not planned. In a matter of minutes the sun would set, or a stray cloud would block the sun. Camera in hand I continued to the top of the hill, hoping to see and not just shoot for the sake of shooting.
On my run today (Tuesday), the leading edge of the cloud shield associated with a cut-off upper level low southwest of the Los Angeles began to move into the area.
Systems such as this are notoriously difficult to forecast and computer models (and forecasters) often disagree. In this case the wetter solution won the day with a half-inch of rainfall being recorded at Downtown Los Angeles (USC) Wednesday evening.
The storm increased December’s rainfall total in Los Angeles to 2.26 inches — about 0.88 inch above normal for the month.