Category Archives: weather

Racing the Sun

Sunset at Ahmanson Ranch.

Racing the sun,
Waiting for rain,
Listening to a meadowlark sing.

From a run at Ahmanson Ranch — now Upper Las Virgenes Canyon Open Space Preserve. Here’s a larger view of the full 16:9 frame.

For an update on this Winter’s austere outlook for rain, see my November 29 Weathernotes.

Southern California 2007-2008 Winter Precipitation Outlook

New grass sprouting amid oaks at Sage Ranch on October 1, 2007

Updated January 10, 2008. The ESRL-PSD Composite ENSO plots page was updated today to correct an issue that resulted in the wrong set of years being used for its Winter La Nina composites. As a result the La Nina composite precipitation map in this post has been updated.

Grasses sprouting as a result of our record setting September rainstorm have brushed our sun parched hills, fields, and woodlands with pleasing hints of green. Whether these areas will remain green depends on how much rain we receive this Fall and Winter.

According to the Climate Prediction Center’s Weekly ENSO Update, issued October 1, La Niña conditions are present across the tropical Pacific and are likely to persist through early 2008. As a result, several longer range U.S. precipitation outlooks are similar to this Nov-Dec-Jan Precipitation Outlook, issued September 20 by the CPC.

The precipitation pattern projected for the western U.S. is typical of a La Niña, with an increased chance of higher than normal precipitation in the Pacific northwest and an increased chance of lower than normal precipitation in the southwest.

The September 20 CPC outlook indicates an “equal chance” of below normal, near normal, or above normal precipitation in the Los Angeles area. However, the La Niña has strengthened recently, so the next precipitation outlook may reflect a more pessimistic projection of Los Angeles area rainfall.

As mentioned above, the ESRL-PSD Composite ENSO plots page was updated today to correct an issue that resulted in the wrong set of years being used for its Winter La Nina composites. This updated precipitation map shows the mean Nov-Mar precipitation for the U.S. during 9 La Niña events from 1948 to the present. Note that the average La Niña rainfall indicated for coastal Southern California is in the 7.0-10.5 inch range, rather than the  10-15 inch range previously indicated in the ESRL-PSD graphic.

The two driest water years recorded in Los Angeles since 1877 have occurred in the last seven years. During the most recent, from Jul 2006 to June 2007, downtown Los Angeles (USC) measured only 3.21 inches of rain. In that context 10-15 inches sounds quite wet! We’ll see.

The photograph of new grass sprouting amid oaks is from a run at Sage Ranch on October 1, 2007.

September Storm

Rocky Peak road 

Los Angeles sometimes gets rain in September, but usually it is the result of tropical moisture from a dissipating hurricane, or perhaps the passage of the tail end of a weakening front. It is rare to see a low as cold, deep and energetic as the upper level low that deluged many areas of Los Angeles county Friday afternoon into Saturday.

Thunderstorms raked the San Fernando Valley Friday night, and several locations in and around the Valley recorded more than an inch of rain over the course of the storm. Los Angeles set a new rainfall record on Saturday, recording 0.40 inch of rain, and rainfall records were broken across the area.

In Southern California the first rain of the season often doesn’t occur until October or November and is always savored. Especially this year, when Los Angeles has recorded only 3.21 inches of rain in the last 15 or 16 months, and a developing La Nina threatens to put the kibosh on Winter rain.

I celebrated the rain by doing an out and back run to “Fossil Point” on Rocky Peak fire road. Based on the size of the mud puddles on the dirt road, this unseasonable storm appeared to be wetter than any in last year’s record dry rain season. Here’s a panorama of the view northwest from the fire road to Oak Ridge, the Santa Susana Mountains and beyond.

Some related posts: San Fernando Valley from Rocky Peak, Rainy Morning on Rocky Peak Road.

Department of Coyote Comportment

Coyote path at Ahmanson Ranch.

With little new growth this Spring and Summer, coyote paths at Ahmanson Ranch have become so well worn that several have recently been posted with “Restoration Area – Please Keep Out” signs. Whether the canny coyotes will choose to cooperate remains to be seen.

Note: Ahmanson Ranch was acquired as open space in part to protect several sensitive species and their habitats. Some (human) use trails have evolved and “Restoration Area – Please Keep Out” signs are a reminder that the area is a preserve.

From a recent run at Upper Las Virgenes Canyon Open Space Preserve (formerly Ahmanson Ranch).

Related post: Trickster

Snowless San Gabriels

Ridge between Mt. Baden-Powell and Mt. Burnham in the San Gabriel Mountains. 
Ridge between Mt. Baden-Powell and Mt. Burnham

Standing on the summit of Mt. Baden-Powell (9399′), I squinted through the haze at Mt. Baldy (10,064′). Nope, no snow.

It’s not often that the highest elevations of the San Gabriel Mountains are snowless on Memorial Day weekend. If nowhere else, there will usually be a patch of white on the north side of Mt. Baldy. Two years ago there were 10-15 ft. drifts on Baden-Powell that persisted into July. Not this year.

This year, usually dependable water sources might not make it through the Summer. On the way to Baden-Powell I  stopped at Little Jimmy Springs. Descending to the spring, I didn’t hear the usual splitter-splatter of water streaming onto the rocks. For a worried moment I wondered if the spring could already dry.

It wasn’t dry, but the spring was nearly as low as it was in August 2002, following the driest water year ever recorded in Los Angeles. Whether Little Jimmy Spring will last through this Summer, after what is likely to be an even drier year, we’ll just have to see. To date, Los Angeles has received only 3.21 inches of rain since July 1, 2006, and will very likely break the record set in 2001-2002.

When on the trail between Islip Saddle and Mt. Baden-Powell, I almost always visit Little Jimmy Spring. The area surrounding the spring is lush and green, and in midsummer is accentuated with the yellows and reds of wildflowers. There are several impressive Incense Cedars nearby, and one huge tree must have enjoyed the idyllic setting and refreshing waters for at least a few centuries. The tree was threatened by the 2002 Curve Fire, but fortunately only a part of its fire-resistant trunk was burned.

At the spring, I filled my Camelbak to the brim. On the way back from Mt. Baden-Powell, I was planning to climb Mt. Burnham, Throop Peak, Mt. Hawkins and Mt. Islip. Most of these peaks are relatively easy ascents requiring short detours from the main trail. Mt. Islip requires a little more effort, and is about a mile by trail from Windy Gap.

According to my Forerunner 205, the distance from Islip Saddle to Mt. Baden-Powell is about 8.1 miles. Depending on how Islip is done, the total mileage including the five peaks is in the neighborhood of 17-18 miles, with an elevation gain and loss of about 4700′.

Note: Angeles Crest Highway (SR2) was open to Islip Saddle.

Related post: PCT Above Windy Gap.

Ahmanson Blue Oak

Photograph of leaves of blue oak in East Las Virgenes Canyon.

Blue oak (Quercus douglasii) is a characteristic oak of the lower elevations of the Sierra foothills and coastal mountains, its range essentially encircling California’s Central Valley.

Based on its reported range, Upper Las Virgenes Canyon Open Space Preserve (formerly Ahmanson Ranch) contains one of the southernmost populations of blue oak within its range. However, the predominate deciduous oak in the area is valley oak (Quercus lobata), and occurrences of blue oak appear to be rare. Regional climate modeling suggests that over the next century the range of blue oak could shift northward and diminish to nearly 60% of its current range.

Blue oak is reported to hybridize with valley oak, however a 2005 study suggests hybrids of these species may be more rare than generally accepted.

The photograph of the leaves of a blue oak was taken on a run along East Las Virgenes Canyon to Lasky Mesa on April 24, 2007. A valley oak immediately adjacent to this blue oak was killed in the 2005 Topanga Fire.

Related posts: Valley Oak Savanna, Laskey Mesa Oak

Technical papers:

Modeled regional climate change and California endemic oak ranges.
Kueppers, L.M., M.A. Snyder, L.C. Sloan, E.S. Zavaleta, and Brian Fulfrost. 2005. 
Proceedings of the National Academy of Sciences of the United States of America, 102(45): 16281 – 16286.

Limited hybridization between Quercus lobata and Quercus douglasii (Fagaceae) in a mixed stand in central coastal California.
Kathleen J. Craft, Mary V. Ashley and Walter D. Koenig.
American Journal of Botany. 2002;89:1792-1798.