Category Archives: nature|clouds

A Few Clouds with Isolated Virga Near 20,000 Feet

Round-bottom clouds

Spotted these unusual clouds while running in Upper Las Virgenes Canyon Open Space Preserve today. Better known as Ahmanson Ranch, the open space area is on the western margin of the San Fernando Valley, northwest of Los Angeles.

The clouds were strikingly similar to clouds I’d photographed last January following the development and dissipation of a band of mid-level mammatus clouds over the San Fernando Valley. As before, the clouds were round-bottomed and were ragged with virga.

Upper air charts and model analyses indicated the clouds were at an altitude of about 20K-25K, and were associated with a very small scale upper level disturbance.

Here’s a wider view of the clouds.

Related post: Mammatus Clouds Over the San Fernando Valley, More posts…

Atmospheric Dynamics

Complex of mountain wave clouds to the north-northeast of Mt. Pinos

These unusual clouds are a complex of lenticular clouds to the north-northeast of Mt. Pinos, photographed this morning from near Mt. Abel. They were produced by strong south-southwesterly winds blowing across the east-west oriented Emigdio and Tehachapi mountain ranges, north of Los Angeles. Here’s another view of these clouds from near the summit of Mt. Pinos.



The winds were associated with the circulation of an unseasonably strong low pressure system off the California coast. The storm system has resulted in measurable rain as far south as Santa Barbara County, and new rainfall records for the date were set in San Francisco, Paso Robles and Santa Maria.



The photographs were taken during a blustery out and back trail run from Mt. Pinos to Mt. Abel on the Vincent Tumamait Trail in the Chumash Wilderness. At the start of the run, the temperature at the Chula Vista trailhead (8400′) on Mt. Pinos was a chilly 39°F. In exposed areas the wind speed was 20-25 mph with gusts to around 50 mph.

Other than the potential for deadfall, the wind wasn’t too bad in the trees. The Vincent Tumamait Trail was in the best condition I’ve seen in years.

Update June 6, 2011. The low that was off the Central California coast Saturday and most of Sunday and an associated cold front set a new rainfall record for June 5 at Santa Barbara Airport, and produced a few sprinkles and showers in the Los Angeles area.

Some related posts: Mountain Weather, Lenticular Wave Clouds, Mt. Pinos – Mt. Abel Out & Back

Mt. Waterman Pines & Clouds

Last Sunday started with light rain in western Los Angeles County, and on the drive to the San Gabriel Mountains, I wondered if the Three Points trailhead would be above the mile deep cloud layer. It was, but barely so, and at the start of the run a couple of scuddy clouds hung over the parking lot.



These were soon left behind, and while the lowlands dealt with damp, dreary weather, my Easter morning run on the PCT continued toward Cloudburst Summit under a bright sun and mostly cloudless skies.

I encountered my first patch of snow a little past Camp Glenwood, on a shaded north-facing slope at about 6300′, nearly three miles into the run. With the above average snowpack, it would have been a surprise not to find some patchy lower elevation snow. Much more snow could be seen on the higher elevation slopes, and the big question was: how much snow would there be on the Mt. Waterman trail?

From Cloudburst Summit I continued eastward on the PCT to Cooper Canyon — one of the most idyllic places in the San Gabriel Mountains. Snowmelt had increased the streamflow, and to start the climb to Buckhorn, two creek crossings were required. It was cool enough that if I could avoid it, I didn’t want to soak my shoes. On the other hand I would rather have wet shoes, than fall bodily into a creek trying to keep them dry. A makeshift trekking pole helped prevent either scenario. Cooper Canyon Falls was spectacular.



On a Summer day this route can be quite warm, and I usually top off my Camelbak at Buckhorn Campground. Good thing it was a cool day — Buckhorn Campground was closed and the water in the campground was turned off. It looked like the Forest Service was doing a major revamp of the campground.

From the campground I still couldn’t tell if the Mt. Waterman trail was going to go. There was a lot of snow on the north-facing slopes, but I was betting it wasn’t going to be as choked with snow as it looked. Worst case, I could turn around, so I decided to continue until there was some reason not to.

There was some snow, and at one point I left the trail to avoid a particularly steep snow slope. About a mile from Hwy 2, the trail worked up onto a broad east-facing ridge, and from that point the trail was mostly free of snow.



No sooner had the snow issue been resolved, when clouds began to spill over the ridges and increase overhead. I knew — or at least thought I knew — that other than decreasing the visibility and temperature, these clouds shouldn’t be a problem. Even so, I was very glad to know the terrain and route well, and have some additional gear in my pack.

The title photograph is from the upper section of the Mt. Waterman trail. The clouds are in the deep canyon between east ridge of Waterman Mountain (8038′) and Twin Peaks (7761′).

Some related posts: Cooper Canyon Cascade & Falls, Manzanita Morning

Follow the Wind, Run to the Sky

Clouds over Lasky Mesa, near Los Angeles

Follow the wind,
Run to the sky.
Find what you’re searching for,
Near or far.

Even in Southern California, Spring can be a fitful beast. This afternoon the temperature was in the low 50s, and the wind was blowing hard enough it was difficult to take a photograph. Just one week ago it had been a stifling 95 degrees — a temperature swing of more than 40 degrees.

Mountain Weather

Orographic lift, waves, and turbulence over the San Jacinto Mountain Range
Orographic lift, waves, and turbulence over the San Jacinto Mountain Range

After last Sunday’s record-setting storm in Southern California, and the cool, unsettled weather during the week, we expected snow conditions on Mt. San Jacinto to be even better than on previous trips this March. But snow conditions — especially backcountry snow conditions — aren’t always what you expect. The new snow, maybe a foot of it, was as thick as wet concrete. If we’d had a little kiwi fruit flavoring, it would have been perfect for shave ice.

A mountain wave cloud near Toro Peak
A mountain wave cloud near Toro Peak.

Even if the snow wasn’t what we had hoped for, the day was extraordinary. Another weak front was moving into Southern California and the strong onshore flow ahead of the front was creating several kinds of interesting mountain weather phenomena — some common and some not so common.

Riding up the tram, we could see plumes of dust blowing across the desert floor east of Banning Pass, and a stack of lenticular clouds hovered over the mountains east of San Gorgonio Mountain. It was breezy at the upper tram station, and from the walkway descending to Long Valley, we could see rimed trees on the southeast side of San Jacinto Peak.

Video of sheets and filaments of turbulence-induced cloud on San Jacinto Peak.
Video of sheets and filaments of turbulence-induced cloud.

We skied up a beautiful untracked drainage south of the Round Valley trail, and eventually worked our way over to Long Valley Creek and then to Tamarack Valley. We were almost to the top of the steep step above Tamarack Valley, and had paused for a moment to look around. There was a distinctive wave cloud to the southeast, and the lower cloud deck was beginning to engulf Toro Peak (8716′). I turned to continue up the slope, and as I looked up, the first of a series of tumbling and twining filaments of gossamer cloud swept past in the turbulent west-northwest flow (video).

Six months ago, also before the passage of a cold front, I’d seen similar clouds on Boney Mountain, in the Santa Monica Mountains. In that case and here on San Jacinto, a moist layer in a stably stratified westerly flow was being lifted over a mountain range. Depending on whether the flow remained laminar, or became transitional or turbulent; a wave cloud, transient wave cloud, or these turbulent thin sheets of cloud might form. In each case the atmosphere was becoming more moist and the clouds were precursors to the formation of a more widespread and persistent cloud layer.

Cygnus Loop Supernova Shockwave
Cygnus Loop Supernova Shockwave

These vaporous, turbulence-induced clouds bear a striking resemblance to interstellar molecular clouds. Both appear to occur in a high-Reynolds-number regime, and each appears to consist of a cohesive, thin sheet of condensate that can be stretched, sheared, undulated and torn. As in the case of its interstellar counterpart, when viewed edgewise, the clouds look like they are comprised of thin, web-like filaments.

The title photo was taken a little below the summit, after ascending the peak. It’s a view to the south, past Jean Peak (10,670′) and Marion Mountain (10,362′), and shows the terrain induced uplift, waves, and turbulence over the San Jacinto mountain range. The flow is from the right to left.

Jet Stream Cirrus

Jet stream cirrus

The long streaks in the photograph above are cirrus clouds embedded in a 125 kt jet stream that was positioned over Southern California Thursday afternoon.



The jet stream was at an altitude of about 30,000 ft. and associated with an upper level low pressure trough off the coast. This trough is the source of the disturbances that are resulting in our latest bout of wet weather.

The jet stream is a key feature of the earth’s atmospheric circulation, and plays an important role in both weather and climate.

For more about jet stream cirrus see A Composite and Microphysical Study of Jet Stream Cirrus Over the ARM Site.

The photographs are from a trail run on Thursday.