From yesterday afternoon’s run in upper Las Virgenes Canyon.
Category Archives: trails|smmc open space
Waiting for Rain: El Nino and the 2015-16 Southern California Rainfall Year
Due in part to El Nino and the Madden-Julian Oscillation (MJO) Southern California jump-started the 2015-16 rain season with above average rainfall in July and September.
Last year the NWS changed the WATER Year to October 1 – September 30, but the RAINFALL Year remains July 1 – June 30, as it’s been for decades.
Below is the monthly tabulation of rainfall for Downtown Los Angeles (USC) for the 2015-16 Rainfall Year, along with what is considered normal for the month.
| Month | Rainfall | Normal |
|---|---|---|
| July | 0.38 | 0.01 |
| August | T | 0.04 |
| September | 2.39 | 0.24 |
| October | 0.45 | 0.66 |
| November | 0.01 | 1.04 |
So far this rainfall year Downtown Los Angeles (USC) has recorded 3.23 inches. Even with November as dry as it’s been we’re still more than an inch above normal for the rainfall year — about 1.46 inches above normal as of November 25.
Over the next couple of weeks the medium range models and other tools aren’t especially bullish on our chances for a good, soaking rainstorm in Southern California. Longer term guidance suggests an improving chance of precipitation as December progresses, and above average precipitation in January and February. We’ll see!
The title photo is from November 3. It shows a band of thunderstorms that moved southward across the San Fernando Valley and into the Santa Monica Mountains. The band produced cloud to ground lightning strikes and some heavy showers. Saddle Peak is in the distance on the left. The shower activity in the distance on the right is in the area of Kanan Rd. and the 101 Frwy.
New Leaves on Drought-Stressed Valley Oak
Sprouting new leaves as if recovering from a wildfire, this drought-stressed valley oak at Ahmanson Ranch benefited from the unusual amount of rain in Southern California during July and September.
Between July 1 and October 1, the Cheeseboro RAWS, located on a hilltop about two miles away, recorded more than two inches of rain.
Here’s what the tree looked like in 2011, before the drought.
Update January 15, 2021. “The Tree” died in the Spring of 2020, when Ahmanson was closed due to COVID-19. Although scorched in the Woolsey Fire, it never recovered from the 2011-2015 drought, and that appears to have been the primary cause of death.
Some related posts: Ahmanson Valley Oaks Battling Drought, It Was So Muddy (Again) That…, A Two Mud Run Summer and Wet Winter Outlook for Southern California
Afternoon Clouds
Wow, there have been some spectacular afternoons recently! That’s the Chumash Trail yesterday.
The Chumash Trail is one of Simi Valley’s best trails. It’s tough and technical, and has great views. From bottom to top it’s about 2.6 miles with an elevation gain of about 1150 feet.
It Was So Muddy (Again) That…
Exactly as I found them — abandoned on the road — on my run at Ahmanson today.
Some related posts: It Was So Muddy That…, A Two Mud Run Summer and Wet Winter Outlook for Southern California
A Two Mud Run Summer and Wet Winter Outlook for Southern California
Ahmanson Ranch gets notoriously muddy when it rains, but it is exceptionally rare for it to rain enough in the Summer to do a run in the mud. Due in part to a warm Pacific, El Nino and a little boost from the Madden-Julian Oscillation in early July, it’s been a record two mud run Summer at Ahmanson Ranch!
The first mud run day was on July 18, when the Cheeseboro RAWS recorded 1.32 inches of rain. That day I ran in the San Gabriels, where the main issue was thunderstorms.
Tuesday (September 15) was a different story. It rained hard overnight — more than three-quarters of an inch — and in the afternoon I did one of my standard weekday loops from the Victory Blvd. trailhead — out East Las Virgenes Canyon, through Las Virgenes Canyon, and up the Beast to Lasky Mesa. It felt more like November than September. After running through a particularly muddy section in Las Virgenes Canyon, heavy plates of mud had built-up on my shoes. Normally I would curse, but on this run I just laughed. It was great to be out in the wet and muck.
Both days set rainfall records at Downtown Los Angeles (USC). July 18 was the wettest day in July and July 2015 the wettest July since recordkeeping began in 1877. September 15 set a new rainfall record for the date and was the second wettest day in September on record. To date, September 2015 is the third wettest September on record. The rain year (July 1 to June 30) is off to a great start in Southern California and the 2015 El Nino has continued to strengthen.
Based on the July-August Multivariate ENSO Index (MEI), for the time of year the 2015 El Nino is one of the three strongest El Ninos since 1950. A survey of dynamical and statistical ENSO models by the IRI & CPC suggests continued warming in the central equatorial Pacific with a peak of the temperature anomaly in the Nino 3.4 region in the OND or NDJ season.
The 2015 El Nino is being compared to the “Super” El Ninos of 1997-98, 1982-83 and 1972-73. It’s too early to tell how the 2015 event will stack up against 1997-98 and 1982-83, but it already has exceeded the strength of the 1972-73 event. How might a Super El Nino affect Southern California rainfall? Historically, they have produced some of the wettest rain years on record. Downtown Los Angeles (USC) recorded 31.01 inches of rain in 1997-98 and 31.25 inches in 1982-83.
The climate context is different than it was decades ago, but very strong El Ninos are different beasts and rev up the atmosphere in a way that dominates global weather. Assuming the 2015 El Nino maintains (or increases) its strength into November or December, it should produce above average precipitation in Southern California this rain season, and perhaps result in an above average rain year for the southern half of the state. This is reflected in the Climate Prediction Center’s latest round of 3-Month Seasonal Precipitation Outlooks, including the Winter outlook for December, January & February 2015-16. We’ll see!
Related post: July Deluge a Preview of Southern California’s Upcoming Rain Season?