Category Archives: clouds

Los Angeles’ On and Off Rain Season is On Again

Clouds over a ridge west of Las Virgenes Canyon

Following a December with twice normal rainfall, Downtown Los Angeles (USC) experienced the fourth driest January-February on record. Now it seems the spigot has been turned back on, and March rainfall for L.A. might very well be above normal.

As of 3:00 p.m. today, March 13, Downtown Los Angeles (USC) has recorded 2.05 inches of rain this March, boosting the rain year total (since July 1) to 9.40 inches. This is about 75% of normal for the date.

More rain is forecast over the next week or so, but the major weather models differ on the projected amounts. To make up for the January-February rainfall deficit and finish the rain year close to 100% of normal, Los Angeles needs another 5.5 inches of rain by June 30.

Not impossible, given some of the forecasts, but that would be a lot of rain for this time of year. Well see!

Update April 12, 2020. Over six consecutive days, from April 5 to April 10, Downtown Los Angeles (USC) recorded 2.96 inches of rain. This is about 325% of the normal amount for the whole month. The precipitation totals of 14.66 inches for the rain year and 14.63 inches for the water year are now above normal for the date and within about one-third of an inch of the normal annual rainfall for Downtown Los Angeles.

Update April 10, 2020. April rainfall picked up right where March left off.  As of April 9, Downtown Los Angeles (USC) has recorded 2.80 inches of rain this month. This is more than three times the normal amount of rain for the entire month of April. This brings the rain year and water year totals to 14.50 and 14.47 inches, respectively. For the first time since February 1 the rainfall totals for Los Angeles are above normal for the date. Los Angeles is now within a few tenths of an inch of normal rainfall for the year, and it is still raining today.

Update March 24, 2020. On March 22, Downtown Los Angeles (USC) set a new rainfall record for the date of 1.51 inches. As of March 24, Downtown Los Angeles has recorded 4.35 inches of rain this month. This is 179% of the normal amount of rain in March. The current rain year/water year total of 11.70/11.67 inches is about 88%/90% of normal for the date. The magic number for 100% of normal rainfall is 14.93 inches — either by June 30 (Rain Year) or September 30 (Water Year).

Update March 17, 2020. As of March 16, Downtown Los Angeles (USC) has recorded 2.80 inches of rain this month. This already exceeds the normal amount of rainfall for the entire month of March, which is 2.43 inches. The current rain year/water year total of 10.15/10.12 inches is about 79%/81% of normal for the date.

Chilly Rocky Peak

Rocky Peak following a cold Christmas storm in 2019.
Rocky Peak

Rocky Peak Road is one of my go-to wet weather running spots. The sandy soil — thanks to the Chatsworth Formation sandstone — doesn’t cake on your shoes when it’s wet. It isn’t entirely mud-free, but as long as you don’t mind a few steep hills, it’s a good choice when the weather turns wet.

According to preliminary rainfall totals tabulated by the NWS, Rocky Peak recorded 1.22 inches of rain during the Christmas storm. The snow level had been forecast to drop to 2000′-2500′ in some areas, so as the storm was breaking up I headed over to Rocky Peak to get in a run, and see what I could see.

I’d dressed for a cool and breezy run, and was comfortable as I worked up the first steep hill. But I hadn’t run half a mile when I stopped and put on some gloves and a pair of stretch shorts. That helped, but the higher I went the colder it got. Up top, a little past Rocky Peak, my thermometer registered a chilly 38 degrees and the wind was gusting 10-15 mph. According to the NWS Wind Chill chart, that put the effective temperature at around 30 degrees.

And that’s what it felt like. Part of the problem was that I was running into the wind, which increased the chill. I had a wind shell in my pack, but once I’d reached my turnaround point and had the wind at my back, it wasn’t needed.

San Gabriel Mountains following a cold Christmas 2019 storm.
Mt. Lukens, Mt. Disappointment, San Gabriel Peak and Mt. Lowe.

There was no snow on Rocky Peak Road or Oat Mountain, but from time to time the setting sun broke through the clouds and highlighted the snow on the nearby mountains. It was a far different scene than on the usual Rocky Peak run.

December has been wet in the Los Angeles area. As of December 27, Downtown Los Angeles (USC) has recorded 4.84 inches of rain this December, which is nearly three inches above normal. Rain year and water year precipitation totals are also well above normal, and at the moment, ahead of last year. We’ll see what the new year brings!

Update January 24, 2020. Well, the new year hasn’t brought us much in the way of precipitation. January in Downtown Los Angeles has been about as dry as December was wet. So far, Downtown Los Angeles has recorded only 0.32 inch of rain this January, well below the climate normal for the date. If there is no additional rain this month, Los Angeles will end the month with about normal rainfall to date for the Rain Year (Jul 1 – Jun 30) and Water Year (Oct 1 – Sep 30). Then we’ll have to see if there is a pattern change in February, or if it is also drier than normal, as most guidance suggests.

Related post: Snow on Oat Mountain (2008)

Looking for Boney Mountain

The Backbone Trail west of Exchange Peak, in the Boney Mountain Wilderness

If you look at the traditional USGS 7.5 minute Triunfo Pass and Newbury Park topographic maps, BONEY MOUNTAIN refers to the large, mountainous plateau that extends roughly from Peak 2417 on the west; to Peak 2793 on the north; and to Sandstone Peak on the east. However, when people say they are climbing “Boney Mountain,” they are usually referring to a high point north of Tri Peaks, on the northwest corner of the plateau, above Newbury Park. This illustration shows these features.

This high point has an elevation of about 2935′ and is typically reached by ascending the Upper Cabin Trail or Western Ridge route. When climbing to this point, most start at one of the Satwiwa trailheads, such as at Wendy Drive and Potrero Road. The high point is NOT the same as “Boney Peak,” which on recent maps is ascribed to a peak adjacent to Inspiration Point, and has an elevation of about 2825′.

Today’s running adventure ascended the Western Ridge route to point 2935 and then worked over to the Backbone Trail, by way of Tri Peaks. Part of today’s adventure was to investigate a peak near the top of the Chamberlain Trail that is labeled peak 2880 on traditional topo maps, but is labeled “Boney Mountain” on many online, GIS-based maps.

The traditional, hand-crafted USGS 7.5 minute topographic maps were produced from about 1945 to 1992, with map revisions continuing until 2006. These maps are now part of the USGS Historical Topographic Map Collection (HTMC) and still widely used. The intended replacements are the GIS-based “US Topo” maps, first released in 2012.

The USGS “US Topo” maps are digitally produced from GIS data. As a result, some features traditionally included in USGS topographic maps — such as trails, landmarks, buildings and recreational features — may not be included. It also appears there have been some issues with geocoding placenames.

The conditions for today’s run were fantastic. Wind-driven clouds condensed along Boney Mountain’s western escarpment, spilling and tumbling over its edge in dramatic fashion.

Clouds spilling over the lip of Boney Mountain's western escarpment.
Clouds spilling over the lip of Boney Mountain’s western escarpment.

As for the other Boney Mountain — Peak 2880 — it was brushy and the rock wasn’t the best, but climbing it did provide some fresh views of the Boney Mountain area. My guess is that the “BONEY MOUNTAIN” label, which described an area on the traditional maps, was treated like a point feature when geocoded. The nearest point happened to be Peak 2880, which speciously became “Boney Mountain.”

In the 2018 edition of the Triunfo Pass US Topo, the Boney Mountain label was moved to Tri Peaks, and the label for Tri Peaks was moved to another, unnamed, peak. In the current online version of the map, the Boney Mountain label and Tri Peaks label are at Tri Peaks. Over time the maps should improve, but until then, I’ll continue to use the traditional 7.5 minute USGS maps, or commercially produced maps that have been field verified.

And what about point 2935 – the high point on the crest that so many people climb? It really deserves a name. Given it overlooks the Danielson Monument and cabin site, maybe something like “Danielson Peak” would be fitting.

Here are a few photos taken on my hike and run.

Some related posts: After the Woolsey Fire: Boney Mountain and Pt. Mugu State Park, An End of Year Boney Mountain Adventure

An Upper-Level Low Sunrise, Shower, and Sunset

Sunset in West Hills, CA, associated with an upper-level low off the coast of Southern California.

It was about 15 minutes before sunrise when I started my run from the trailhead at the “Top of Reseda.” After running up to Mulholland and partway down Fire Road #30, I could see a batch of tropical-looking clouds to the southeast. These were associated with a cutoff upper-level low that had formed off the coast of Southern California on Halloween.

The behavior of cutoff upper-level lows is difficult to forecast. They are usually separated from the general west to east flow and typically wobble around like a spinning top. A cutoff low can remain off the coast for several days or more. Just where they wobble can dramatically impact the weather. So far this morning, the only effect of this weak low had been to embellish the sunrise with a few clouds, but such lows can be capricious, and this one was no exception.

My first stop was going to be Temescal Peak, and I picked up the pace a bit, curious to see how the clouds and sunrise might look from that viewpoint. Temescal Peak is just off the Backbone Trail, near its junction with Temescal Ridge Fire Road. On a clear day this tiny peak affords an exceptional 360-degree view that can include Mt. Baldy, San Gorgonio Mountain, San Jacinto Peak, Mt. Pinos, Hines Peak, and other area landmarks.

Sunrise over West L.A. from Temescal Peak in the Santa Monica Mountains.
Sunrise over West L.A. from Temescal Peak in the Santa Monica Mountains.

Turning left at the Hub, it didn’t take long to get to Temescal Peak. Westward from the peak, a veil of smoke could be seen in the vicinity of the Maria Fire. Nearby, some of the canyons in the area of the Getty Fire were filled with a smoky haze. In the distance, a few mercurial clouds were scattered across the eastern sky.

At the time, I couldn’t tell if the clouds were approaching or receding, developing or dissipating. Returning to the Hub, I turned left on Eagle Springs Fire Road and began the descent toward Trippet Ranch. On the way, it became clear the clouds were headed my way. By the time I’d run to Trippet Ranch and up to the top of the Musch Trail, the band of clouds covered much of the eastern sky.  Virga streamed from the bases of some of the clouds, and  I wondered if a few rogue drops might be reaching the ground.

Developing clouds associated with an upper-level low along the coast of Southern California.
Developing clouds from near the top of the Musch Trail.

Over the remainder of the run — past Eagle Rock and through Garapito Canyon — the clouds continued to move overhead. A few drops of rain found me near the end of the run, but the most pleasant surprise occurred on the drive home, when showers dampened the  streets of the western San Fernando Valley.

There had been no rain in the Los Angeles area this October, and the showers reminded me of the erratic nature of Autumn precipitation in Los Angeles. Even though “normal” rainfall in October at Downtown Los Angeles (USC) is 0.66 inch, no one familiar with L.A. weather is surprised when October is dry. Over 143 years, Downtown Los Angeles has recorded no October rainfall 26 times, 0.10 inch or less 54 times, and 0.25 inch or less 74 times.

The upper-level low continued to influence the day’s weather, and while the low remained mostly offshore and didn’t generate any more showers in the West Valley, it did produce a colorful sunset!