Mt. Baldy fron the summit of Mt. Baden-Powell

Yesterday, Woodland Hills topped the 90° mark for the first time this year. But somebody forgot to tell the local mountains about the warmup. This morning, I was about a mile into an out and back trail run from Islip Saddle to Mt. Baden-Powell, and with the wind chill, it felt like the temp was in the 40's.

Eagle Rock From Eagle Springs Fire Road

Is it May or March? With all the blustery weather systems that have been moving through Southern California, it's been hard to tell.

Today I had planned to head back to the high country of the San Gabriels, but instead decided to take advantage of the spectacular weather and do a rambling 24 mile run in the Santa Monica Mountains.

It was a good choice. Early in the run growing mountains of silver-lined cumulus towered above the Hub, and a brisk wind tempted me to pull the sleeves from the pack. Wildflowers lined the trails, and the chaparral teemed with color, sound and scent. It was a long run kind of day.

Note: Later in the day I talked to a runner who had been at Lake Arrowhead early in the morning. He said it had been snowing down to 3000 ft! According to the NWS, record low temperatures for today were set at Lancaster (41°), San Luis Obispo (38°), and Sandberg (28°).

We've had some great running weather in Southern California this Spring, with more than our usual share of cool days and postcard skies. Remarkably, the highest temperature recorded at Downtown Los Angeles so far this year was in the final few days of Winter, when the temperature hit 88 on March 16.

The title photograph is from a recent run in the Simi Hills.

I heard a news report the other day that Southern California's rain season would end in two weeks. While Southern California typically receives the bulk of its precipitation in the months of November through April, the rain season doesn't turn off like a switch on May 1. There certainly can be significant rain in May, and even June.

The water year for Downtown Los Angeles (USC) is from July 1 to June 30 of the following year. So far, Downtown Los Angeles (USC) has recorded 16.17 inches of rain during the current water year. This is more than an inch above the 1971-2000 annual climate norm for Los Angeles of 15.14 inches.

Our Sunday-Monday storm put Downtown Los Angeles at 1.51 inches of rain for the month of April -- well above the climate normal of 0.83 inches. The normal amount of precipitation for May is 0.31 inches, and for June is 0.06 inches. But those are just averages. On occasion we receive much more than this, and sometimes much less. On the up side, according to NWS data, in April 1965 Los Angeles recorded a total of 6.02 inches of rain. In May 1921, 3.57 inches was measured; and in June 1999 0.98 inch was recorded.

Although the current El Niño has weakened, convection is still somewhat enhanced in a broad region of the equatorial Pacific, and the MEI, ONI, and GWO indicate the continued presence of El Niño. This could result in more active Spring weather than usual, and more opportunities for rain in Southern California.

At the moment, the next opportunity for some Southern California rain looks to be next week, around Tuesday or Wednesday. We'll see!

The title photo is from a run on the Chumash Trail at the end of March.

Because of their unusual "flying saucer" appearance, lens shaped lenticular clouds have long drawn attention. According to a research article in Weather, depictions of wave clouds appear in Gothic art from the 15th century.

Lenticular clouds typically form when wind flows into, and then up and over a mountain range, creating a series of "roller coaster" atmospheric waves downwind of the range. Lenticular clouds can (but don't always) form in the peaks of the waves, as a layer of air rides up a wave, and cools and condenses. The waves are called standing waves because the peaks and troughs can stay (more or less) in the same place for hours at a time.

The rising air on the windward side of a lee wave can be soared by gliders to high altitudes. According to the FAI, the current world absolute altitude record for gliders is 15,460 meters (50,722 ft.). This record was set by the late Steve Fossett in 2006, soaring a mountain wave in the Andes. Mountain wave soaring was pioneered on the east side of the Sierra, and several single place sailplane world altitude records have been set soaring the Sierra wave.

Lee waves also have a nefarious side. Rotors, breaking waves, and other phenomena associated with mountain waves can create extreme turbulence. A sailplane destroyed in early research on rotors was estimated to have experienced 16 g of acceleration. According to the Australian Transport Safety Bureau, "clear air turbulence associated with a mountain wave ripped apart a BOAC Boeing 707 while it flew near Mt. Fuji in Japan. In 1968, a Fairchild F-27B lost parts of its wings and empennage, and in 1992 a Douglas DC-8 lost an engine and wingtip in mountain wave encounters."

The wave clouds above were photographed northwest of Los Angeles during a trail run earlier this month. The wind forming the wave clouds appears to be from the north-northeast. The situation was peculiar because the wind at nearly all levels at that time was from the northwest. The tops of the wave clouds are being sheared by winds blowing from the northwest (left to right).

Here's an animated series of NRL satellite photos showing the waves pictured above, and the complex wind and wave pattern at the time of the photograph.

Pushed up and over Boney Mountain's two thousand foot western escarpment, Pacific winds condense into thick cloud along its jagged crest. At times breaking free of the mountain's grasp, patches of cloud drift eastward, creating a patchwork of sun and shadow on the steep slopes, and in the valley below.

In the distance, the Ventura Mountains gleam with a mix of snow and cloud, and below the fields of Satwiwa stand out vibrant and green. At my feet hundreds of purple shooting stars dance in the wind; and nearby yesterday's rain seeps and trickles from moss to lichen on the scraggy volcanic rock.

It is a remarkable morning, and an exceptional one to be doing the Boney Mountain north side loop. Here's a short HD video of some of the views along the way. (If the video doesn't play cleanly the first time through because of bandwidth issues, let it finish and then try playing it a second time.)

The weather has calmed in Southern California. Medium range models are forecasting a break of about a week in what has turned out to be a very busy rain season. Over the last 90 days a precipitation pattern typical of El Niño has emerged in the western U.S. This is reflected in rainfall total for Downtown Los Angeles (USC), which is now at 13.2 inches for the water year -- 4.78 inches above normal.

The dry weather could not have come at a better time for those affected, or threatened, by mudslides and debris flows. This small slump along a road at Ahmanson Ranch is indicative of the instability that can develop when soil becomes saturated. Had our recent wet pattern been more persistent, mudslides and debris flows might have been much more widespread and devastating.

One of about a dozen vernal pools in the Rocky Peak area. More than just a puddle, these rainy season pools form as a result of the area's unique geology.

In my experience, excessive rainfall is not necessary for the pools to form. Normal month-to-month seasonal precipitation is usually sufficient. Their persistence depends on several factors, but in a season with normal to above average precipitation, the pools can last for several months.

From Wednesday's run on Rocky Peak.

Related post: Vernal Pool at China Flat

Computer models and other tools continue to forecast a shift to an "El Nino like" upper flow pattern next week that could result in an extended period of wet weather in Southern California. I'll be updating Southern California Weather Notes on Wednesday with additional info.

The photograph of patterned altocumulus clouds is from this afternoon's trail run along the northern boundary of Ahmanson Ranch, near Los Angeles.

Following the little bit of wet weather we had at the end of the year, Southern California has been enjoying idyllic weather with highs in the 70's and 80's. Southland cities recorded the highest temperature in the continental U.S. several days this week. Tuesday San Diego recorded a high of 84 degrees, tying Kalaeloa, Hawaii for the warmest temperature in the nation.

The weather's been great for trail running -- and for the chaparral plants. Alternating periods of wet weather and warm weather have encouraged growth and flowering, and I've been seeing a number of rainy season wildflowers. In addition to the milkmaids in the photograph above, some of the early bloomers include nightshade, peony, shooting star, woolly blue curls, prickly phlox, chaparral mallow, rattlesnake weed, and several others.

Rainfall totals in Southern California this rain season to date have generally ranged from an inch or so above normal to an inch or so below (WRCC). As of yesterday, Downtown Los Angeles (USC) precipitation was 0.56 inch above the norm for the water year to date. Although January has been dry so far, it looks like we may see a shift to more seasonable -- and wetter -- weather around midweek next week.

The precipitation pattern we've seen on the West Coast so far this rain season has a bit of an El Nino flavor to it, and that pattern may become better defined in the coming weeks. Today's 6-10 day and 8-14 day precipitation outlooks from the Climate Prediction Center indicate above average rainfall for Southern California. We'll see!

Got caught in some showers this afternoon on Rocky Peak, returning from a rambling trail run from the San Fernando Valley over into Simi Valley.

This was one of those "not sure where I'm going" runs that unfolded as it progressed. It started near Chatsworth Reservoir at Chatsworth Oaks Park, worked over to Santa Susana State Historic Park, then up the Old Stagecoach Road. At the top of the old Stagecoach Road, I picked up the Upper Stagecoach Trail and followed that to Santa Susana Pass and the 118 Frwy. From there it was a short distance down the west side of Santa Susana Pass Rd. to the Lower Stagecoach Trail, which took me to Corriganville.

Once down in Simi Valley there are four trails that ascend to Rocky Peak road, and my return route. From the shortest to the longest, they are the Wildlife Corridor trail, Hummingbird Trail, Chumash Trail and the Marrland/Las Llajas trail. Not sure how long it would take to get back to the SFV, I finally decided on the Chumash Trail.

Running up the Chumash Trail, the wind picked up, the clouds began to lower and thicken, and the temperature dropped. Minutes after turning right onto Rocky Peak road the showers began, and it wasn't long before the sleeves came out of the pack.

The return trip, with a net elevation loss, went a little quicker than expected. Next time I'll have to give the Las Llajas option a try. That would extend the run from about 17 miles, to something over 20. The approximate elevation gain/loss on the 17 mile version was a little under 3000 ft.

Related post: Old Santa Susana Stage Road

Some outstanding evening runs this week. Did a FiveFingers run out at Ahmanson on Tuesday, and as sometimes happens this time of year, didn't make it back before dark. Was up on Lasky Mesa in the fading light, with endorphins at full flow. In a distant grove oaks I could hear a Great Horned Owl, and with each hoot-whoo it seemed the zeal of the day was turning to the tranquility of the night. The running was effortless and ethereal.

This evening's run was also superb. Over the course of the run, the skies had become increasingly gray and troubled, as a weak cold front approached the area. Climbing a long hill, the light was dank, and I had given up on the sun. But as I neared the crest of the hill, orange-red sunlight began to illuminate the clouds from below, highlighting a sunset shower. Large, cold rain drops began to patter around me, and I watched mesmerized, as the light, clouds, and rain played on the sky.