Less than a week after the rain in Southern California, grasses and other annuals are sprouting, and open space areas are starting to turn green.
From a run at Ahmanson Ranch this afternoon.
Category Archives: weather|southern california
Smilo and Sun
The first day of sun following rain on Tuesday and Wednesday. Ahmanson Ranch was not nearly as wet and muddy as I expected, and although water was pooled in Las Virgenes Creek, the stream was not running. Would have been a very different scenario had this storm occurred later in the rain season. Some rain totals for the Los Angeles area and comments about the developing El Nino are in my October Weathernotes.
The soft trail conditions were nearly ideal for barefoot running, and I took my running shoes off part way through the run. The muddy sections were great fun, and running barefoot was a enjoyable way to put a wrap on the rain event. I can’t wait for it to rain again!
The grass backlit by the sun is smilo (Piptatherum miliaceum). Introduced into California over a century ago, smilo is a drought resistant grass that has been used for pasture, and for erosion control following fires.
Chasing Towhees and Other Rainy Day Activities
Did an enjoyable run at Sage Ranch today that started and ended in showers, but also included a few moments of subdued sun.
The shrub with the yellow-orange leaves is rain soaked poison oak. As I took the photo, a California towhee landed in its limbs, probably a little concerned about the unexpected house guest. From a towhee point of view, a thick chaparral shrub is a homey place with all of the creature comforts.
In chaparral areas towhees are common, and I frequently see them on my runs. Over years of running I’ve learned some of their habits.
Many times when I encounter a towhee on the trail, it will flutter and scurry along the ground just ahead of me, and then dart into a bush. Although not as dramatic as the broken wing act of a killdeer, this “catch me if you can” behavior is probably intended to draw a potential predator away from the bird’s nesting and living area.
Very different animals will often cooperate to benefit each other. In the case of a towhee, one of its best buds is apparently the cottontail rabbit. On occasion I will see the bird and rabbit foraging together on a trail. When trying to keep a wary eye out for potential predators, four eyes are much better than two.
Where there is one towhee, there will often be another nearby — presumably its mate. At Sage Ranch, I’ve repeatedly encountered a pair of towhees near a particular shrub over a period of several years.
Rocky Peak Rainstorm
Clouds swirled around me as I worked up the steep trail toward an overlook near Rocky Peak. I stopped and listened to the patter of the rain against the rocks, its intensity rising and falling with the gusts of wind.
The wind-driven rain trickled down my face, tasting cool and clean. It didn’t matter that my running clothes were soaked and that with each gust I could feel a chill. It was raining!
In the same manner that a color will sometimes appear especially pure and vibrant, there was an unusual liveliness to this rain.
Southern California Rain and the 2009-2010 El Niño
Who would think a western Pacific typhoon could so directly affect California’s weather? But that’s what is happening. The moisture from typhoon Melor, which was over Japan just a few days ago, was captured by an extending and strengthening jet stream. This has resulted in an atmospheric river of moisture, stretching across the Pacific and into California.
This morning, Intellicast composite radar shows Northern and Central California already being hammered by the system. Southern California has seen a few showers, and several stations have already recorded significant rainfall. As of 9:00 a.m. the CNRFC Precipitation Map shows isolated 24 hr. rainfall amounts in the foothills and mountains of Santa Barbara, Ventura, and Los Angeles County ranging from about 0.16 inch at Sandberg to 0.61 inch at West Big Pine.
The last day there was measurable rainfall at Downtown Los Angeles (USC) was on June 5, 2009, when 0.13 inch was recorded. Computer weather models forecast the best dynamics and highest rainfall totals will be in the northern two-thirds of the state, but in recent days have been trending wetter in the Los Angeles area, particularly in the mountains.
With so much moisture in the atmosphere, it takes very little lift to produce rain. Onshore winds, full of moisture, are lifted by foothills and mountains across the flow, and the result is rain — sometimes lots of it. In this case it appears the south to west facing mountains and foothills of Santa Barbara, Ventura and Los Angeles counties may record much higher rainfall totals than the lowland areas.
In a decade characterized by unusual El Ninos, the ongoing El Niño of 2009-2010 is another strange one. El Niño signals continue mixed. The Aug-Sep Multivariate ENSO Index (MEI), decreased from 0.978 to 0.754, however other El Niño signals appear to be rebounding. In the last two weeks low level equatorial westerly anomalies have increased significantly. The reduction in the strength of the trade winds, and a downwelling Kelvin wave resulting from a very strong westerly wind burst already appear to be increasing upper ocean heat content in the central equatorial Pacific. The 30 day moving Southern Oscillation Index (SOI) has been dropping, and should return to negative territory in a day or so.
Recurring equatorial westerly wind bursts and enhanced west-central Pacific convection has been slowly migrating eastward. The most recent round of enhanced convection was centered at about 160E. This is consistent with a developing El Niño, and may have contributed to the creation of the atmospheric river now affecting California, by helping to extend the Pacific jet stream following an East Asian mountain torque event.
However, total and relative AAM remain negative, and are lower than is generally the case during a developing El Niño. Of the weak to moderate El Ninos that have occurred Since 1959, only the 1977-78 and 1994-95 El Niños have had negative average July-September relative AAM values comparable to the current El Niño. Since 1959, only 4 of 15 El Niños have had negative average relative AAM values during the Southern California rain season of November to March. (Revised 12/14/09)
Moderate El Niños come in many flavors and have varying impacts. Under the guise of such El Niños Los Angeles experienced its second wettest water year on record in 2004-2005, when 37.25 inches of rain was recorded; then in 2006-2007 had its driest water year on record, when only 3.21″ was recorded. What flavor will the 2009-2010 El Niño be?
The photo of the tree and clouds is from yesterday’s run at Ahmanson Ranch.
Related post: How Does the El Nino of 2009-10 Compare to Other Warm ENSO Episodes Since 1950?
Ramping Down for Mt. Disappointment
Note: The Mt. Disappointment Endurance Run is now the Angeles National Forest Trail Race.
Or should that be ramping UP for Mt. Disappointment? Anyway, started tapering for the Mt. Disappointment run next Saturday. Did the 13 mile Cheeseboro Canyon keyhole loop from the Victory Trailhead of Ahmanson Ranch yesterday, and then stretched the legs at Sage Ranch today. Both mornings were cool, with low clouds and fog — very pleasant!
Here’s hoping for “not too hot” weather for the race. At the moment, the GFS and ECMWF weather models show a weak upper level trough moving through California in the Friday-Saturday timeframe. Such a scenario should increase the chances of “seasonable” temps for the race — which would still be quite warm, but maybe not crazy hot.
Update Friday Morning 8/07/09. Broad upper level trough over California this morning is keeping things cool. Yesterday the high recorded at Mt. Wilson was 70, and the low overnight was 48! Southern part of the trough is forecast to hang back over Southern California through Saturday, which could result in temps a little BELOW normal for the Mt. Disappointment race. We’ll see!
Related post: Mt. Disappointment 50K 2008 Notes