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Los Angeles Rainfall Above Normal, But…

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Study of mud on the Musch Trail in Southern California

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!

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The Tree

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Drought-stressed Valley Oak at Ahmanson Ranch - The Tree

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.

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Advancing Clouds

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leading edge of the cloud shield associated with a cut-off upper level low southwest of the Los Angeles. December 20, 2016.

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.

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Glimpse of Autumn

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Oaks and clouds Upper Las Virgenes Canyon Open Space Preserve

I was running in the hills along the western margin of the San Fernando Valley and reveling in the Autumn-like weather. The hills were parched, brown, and the soil dessicated. In 128 days it had not rained.

An area of low pressure was producing some clouds and even a little rain in some parts of Los Angeles County. The last time it had been this cool in the afternoon was in mid-June. The pleasant temperature was a welcome change from the 80s, 90s and 100s of Summer.

Precipitation from the 2015-16 Godzilla El Nino fell short of expectations, with Downtown Los Angeles only recording 65% of normal rainfall and the drought continuing into its fifth year. How long would we have to wait  until we received widespread rainfall?

At the moment the expectation is for ENSO Neutral conditions to prevail this Winter. Neutral conditions give forecasters little leverage on which to base their Winter outlook, but based on last year’s Southern California precipitation forecasts, we didn’t have much leverage then either.

With a warming planet, we appear to be in a new regime. Forecasts based on 1950-2000 analogs may no longer be applicable. As of September 15 the Climate Prediction Center’s Precipitation Outlook for Southern California for December, January and February is the equivalent of flipping a three-sided coin.

We may just have to wait and see what the Winter brings.

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Heat Training Hold

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Warming Hut and Golden Gate Bridge at sunrise from the Golden Gate Promenade

I squeezed the bag of ice wrapped in the bandanna around my neck and shivered as an ice cold bead of water snaked down my spine. The temperature reading from the shaded sensor clipped to my pack read 106°F.

Sunrise from the Golden Gate Promenade near the Warming Hut and Fort Point Pier, also known as Torpedo Wharf.
Sunrise on Golden Gate Promenade near Fort Point Pier

That had been at 3:30 Thursday afternoon at Ahmanson Ranch. Earlier that day the “in the sun” temp recorded at the nearby Cheeseboro RAWS had topped out at a blistering 119°F!

This morning, Sunday morning, my AC100 heat training was on hold. The sun had just risen and I was running on the dew-covered sidewalk of the Golden Gate Bridge. The temperature sensor was reading about 54 degrees cooler than at Ahmanson — an almost chilly 52°F.

Not to worry — I would be back running in the 100 degree Ahmanson heat Tuesday.

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What’s the Current Weather on the AC100 Course?

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Pacific Crest Trail on Kratka Ridge in the San Gabriel Mountains

A couple of weekends ago we had cool weather for a 28 mile Angeles Crest 100 training run from Islip Saddle to Chilao Flat. It was a bit windy and chilly at Islip Saddle, but once we were up and over the shoulder of Mt. Williamson the wind settled down and the weather for the remainder of the run was near perfect.

This was the second of four supported AC100 training runs, each covering a different section of the course. These organized runs account for just a tiny fraction of the total mileage a runner does to prepare for this event, and much of the mileage is done on the AC100 course.

Where is the AC100 course? Incorporating segments of iconic trails such as the Pacific Crest Trail, Silver Moccasin Trail and Gabrielino Trail, the AC100 starts in the mountain community of Wrightwood, California and ends in Altadena near JPL, traversing a large part of the San Gabriel Mountains.

Mountain weather — even Los Angeles County mountain weather — can be extremely varied and changeable. At about mile 18 the AC100 course reaches an elevation of more than 9,200′, near the summit of Mt. Baden-Powell. On the same day temperatures on the course can differ by 50 degrees or more. One section can be inundated by a flash flood while another is bone dry. During a Spring training run it might be 100 in the sun at Echo Mountain, while it is snowing on Baden-Powell.

Annotated Mt. Wilson Towercam Image
Annotated Mt. Wilson Towercam Image

The Mt. Wilson Towercam is usually pointed in the direction of the Angeles high country. When it is, it provides a great overview of about two-thirds of the AC100 course. The view extends from the top of the Acorn Trail at about mile 4 (in the distance on the far right), along the crest past Mt. Baden-Powell, Throop Peak, Twin Peaks and Waterman Mountain to Three Points at about mile 43. Chilao is hidden from view, but the Charlton Flat area and a section of Edison Road is visible on the left. Newcomb Saddle, at about mile 68, is on the lower right. Here’s an annotated Towercam image that shows the approximate location of these features.

Bill Westphal’s Altadena Weather & Webcam gives a lower elevation view of the San Gabriels, near the AC100 Finish. The view is NE toward the Sunset Ridge Trail and Mt. Lowe Road, around mile 93 or 94. The course goes from the right of the photo to the left, but is mostly hidden from view.

If you are willing to jump through some Java security hoops the Mountain Hardware Live Interactive Cam in Wrightwood is a couple blocks from the AC100 Start. It has views of downtown Wrightwood, Wright Mountain, the Heath Canyon landslide, Blue Ridge and several other locations. I temporarily enabled Java and followed the troubleshooting info linked on the web cam page. I’ve been able to get it to work on a desktop system using Firefox or Internet Explorer. Note that enabling Java and adding non-secure URLs to the Java exceptions list decreases the security of your computer.

Following are several Remote Automated Weather Stations (RAWS) and Weather Underground Personal Weather Stations (PWS) along or near the AC100 course, in order from Start to Finish.

It is important to note that the air temperature given by RAWS stations is the temperature inside a sun-shielded, ventilated enclosure 4-8 feet off the ground. Basically it’s the temperature in light shade. The temperature in full sun can be 15°F higher. I’ve found the “Fuel Temperature” to be a better gage of how hellish it’s going to be on exposed areas of trail. (The Fuel Temperature is the temperature of a ponderosa pine dowel in direct sun.)

Wrightwood KCAWRIGH7 PWS (5996′) – Approximately 0.25 mile W of Start. Was 55°F at 5 a.m. for 2015 AC100.

Wrightwood KCAWRIGH9 PWS (6000′) – Approximately 0.6 mile SE of Start. Was 59°F at 5 a.m. for 2015 AC100.

Big Pines BPNC1 RAWS (6964′) – Off Hwy 2 near Mountain High Ski Area. Top of Mt. Baden-Powell can be 12+ degrees cooler and much more windy. Was 64°F at 6:54 a.m. for 2015 AC100. Fuel temp at 11:54 a.m. was 92°F.

Mountain High Ski Area Base & Top Conditions – Approximate elevation of Base is 7000′ and top is 8000′. Compare Base temp to Big Pines temp.

Chilao CHOC1 RAWS (5450′) – Approximately 1.25 miles WNW of Chilao aid. Fuel temp at 1:53 pm was 95°F for 2015 AC100. Air temp at 6:53 pm was 79°F.

Clear Creek CEKC1 RAWS (3000′) – Approximately 6.8 miles W of Shortcut Aid (~4793′) and 2.9 miles W of Red Box Aid (~4620′). Was 71°F at 8:54 p.m. for 2015 AC100.

Mt. Wilson MWSC1 (5710′) – Approximately 1.5 miles NW of and 780′ above the top of Mt. Wilson Toll Road (~4930′). Compare to JPL 5600′. Was 69°F at midnight for 2015 AC100.

Henninger Flats HNGC1 RAWS (2800′) – Approximately 0.8 miles WSW of Idlehour Aid (~3168′). Marine layer can increase humidity on this section of the course. Was 69-70°F from 4 a.m. to 7 a.m. for 2015 AC100. Fuel temp was 89°F by 11a.m.

Altadena KCAALTAD18 PWS (1214′) – Approximately 0.6 miles S of Finish. For 2015 AC100 temp ranged from 66°F at 2 a.m. to 63°F at sunrise. Temp was 79°F at 9 a.m., 82°F at 11 a.m., and 86°F at 1 p.m. Humidity was high with dew point about 70°F.

Altadena KCAALTAD41 PWS (1348′) – Approximately 0.4 miles NW of Finish.

It’s not on the AC100 course, but the Mt. Baldy Ski Lifts Web Cams and Weather can be useful for estimating mountain temps and for Baldy area training runs.

Related post: The Ups and Downs of the Angeles Crest 100 Mile Run