Fogbows form opposite the sun in a manner similar to rainbows, except the water droplets that create a fogbow are much smaller than raindrops. Because a fog droplet is so small, the physics of the interaction is different. The result is often a diffuse, primarily white bow.
The photograph of the fogbow was taken Sunday morning on an out and back run from Wendy Drive to Mugu Peak. The sun was about 14 degrees above the horizon. More about fogbows and other atmospheric phenomena can be found on Les Cowley’s Atmospheric Optics website.
Hikers, riders, and runners reveled in the unseasonably cool afternoon temperatures at Ahmanson Ranch (Upper Las Virgenes Canyon Open Space Preserve) yesterday.
According to the NWS, the high temperature of 75 degrees at Woodland Hills (Pierce College) was the lowest for the date on record. The temperature at the Cheeseboro RAWS didn’t reach the 70s until around 1:30 p.m., and finally hit 75 around 4:30 p.m. Earlier in the day, the station recorded 0.03 inch of light rain.
I took advantage of the cooler weather to do an out and back trail run from the Victory Trailhead to Cheeseboro Canyon. The nine mile run has an elevation gain/loss of around 1000′. Except for a couple of hills, it’s a relatively fast-paced route, particularly on the way out to Las Virgenes Canyon. There are two creek crossings in Las Virgenes Canyon. These dried up earlier this year, but in some years the crossings have enough water to get your shoes wet.
It’s not a good run to do when it’s hot, and in the Summer Ahmanson is almost always hot. In-the-sun temperatures are typically above 100 degrees, and sometimes reach 110 degrees or more. More than once I’ve encountered people on Ahmanson area trails that misjudged the conditions and were out of water. And sadly, dogs are especially susceptible to heat.
Here’s an interactive, 3D terrain view of the run. The map can be zoomed, tilted, rotated, and panned. To change the view, use the control on the upper right side of the screen. Track and placename locations are approximate and subject to errors. Poor weather, and other conditions may make this route unsuitable for this activity.
Those that recreate at Ahmanson will recognize the title photo as East Las Virgenes Canyon, about 1.1 mile from the Victory Trailhead. This is where a trail/road to Lasky Mesa forks off the main road.
Was that thunder? I warily eyed the dark clouds over the mountains and pondered the situation.
I was about halfway to the top of the Chumash Trail and was planning to run along the crest to Rocky Peak. The run had started in short sleeves and sunshine, but it was pretty obvious that wasn’t going to last.
Chumash Trail about a mile from the trailhead
A cold upper-level low had brought badly needed rain to the area for the past two days. The low was moving off to the east, but there was still a chance of afternoon showers and maybe even a thunderstorm.
It was the “thunderstorm” part that I needed to pay attention to. I had enough gear to deal with a downpour and cooling temps, but electrical storms are no fun at all.
I decided to continue to the top of the Chumash Trail and reassess. As I worked up the trail, I pictured the counterclockwise circulation around the low, and how convective cells develop over the mountains and then dissipate as they drift south. The concern was that the cells don’t always dissipate.
Rocky Peak Road near Rocky Peak
It looked like things weren’t getting any better at the top of the Chumash Trail, but it wasn’t worse either. I hadn’t heard any thunder for a while, and most of the activity seemed to be a few miles to the west and east. Having been starved of stormy weather for much of the rain season, I turned right on Rocky Peak Road and headed south toward Rocky Peak.
The run from the Chumash Trailhead to Rocky Peak is a challenging mix of technical single-track trail and hilly fire road. There are wide-ranging views of Simi Valley & Simi Hills, the San Fernando Valley, Santa Monica Mountains, Ventura County mountains, and San Gabriel Mountains. On a clear day, the view can extend to the Channel Islands, Saddleback, and San Jacinto Peak.
NOAA radar mosaic at the time I was on Rocky Peak
The actual turnaround point for a run to “Rocky Peak” varies. Some like to turnaround at the high point of Rocky Peak Road that is near Rocky Peak. Most of the time, I turnaround at a viewpoint that is at the end of a spur trail that branches off from the high point of Rocky Peak Road. From time to time, it’s fun to hike over to Rocky Peak and scramble to the top. That’s a bit more involved and requires some route-finding.
I felt the first raindrops as I reached the high point on Rocky Peak Road and turned onto the spur trail that leads to the overlook. There was some increased development to the east, but it looked like there would be enough time to get over to Rocky Peak, take a couple of pics, and then head back.
Oat Mountain, shrouded by rain
I felt a little exposed on top of Rocky Peak. I hadn’t heard any thunder for the past hour, but a cell to the east was spouting heavy rain over the San Fernando Valley, which meant there was probably enough development to produce lightning. I took the title photo and a couple of others and hurriedly descended from the peak.
Back on Rock Peak Road, the sprinkles increased, and the showers became more steady as I ran north toward the Chumash Trail. Under the dark clouds, a raven perched on a large pinnacle cawed incessantly, either enjoying the rain or complaining about it. In the distance, a siren wailed down in the valley. It was cold, and I was very glad to have an extra shirt, sleeves, gloves and a light rain shell.
Mix of sun and rain on the Chumash Trail.
As I began the descent of the Chumash Trail, the sun briefly broke through the clouds, reflecting brightly on the wet sandstone rocks. I breathed deeply, relishing the smell of the cleansed air and wet chaparral, and continued down the trail.
It looks like Downtown Los Angeles (USC) is going to end February — one of the wettest months of the rain year — with only a trace of rain. The current rain year total for Los Angeles is 4.39 inches, which is about 39% of the normal total for this date.
It’s been one of those years where missed rain opportunities have often turned into strong offshore wind events. This chart from MesoWest shows the wind speed and direction for the past 30 days for the Malibu Hills RAWS. Since mid February there has been five wind events with sustained wind speeds over 30 mph and gusts over 50 mph.
Current forecasts suggest Los Angeles will see at least some rain in March, with the first chance around midweek. We’ll see!
