California Rain and Windstorm: Round 2

California Rain and Windstorm: Round 2

A Mini Blog

The second of three systems to impact central and northern California is winding down as of mid-day this Friday. Rainfall and winds have not been quite as impressive as forecast (so far) although the third and final of the storms, which is expected to arrive Saturday night and early Sunday, may make up for what the first two systems lacked.

Last Tuesday (November 27th) the GFS was forecasting that the three storms beginning Wednesday morning and ending Sunday evening would produce a large swath of 10”+ rainfall over central and northern California with local amounts of 15-20” in the wettest locations of the Santa Cruz Mountains (south of San Francisco), and the coastal mountain ranges north to the Oregon border as well as east to the foothills of the Sierra Nevada and Cascades in the northern third of the state.

The first storm on Wednesday was a quick mover and dropped only modest amounts of rainfall across the region, generally .25”-.50” in the lower elevations and 1.00” in the wettest locations. Although the second storm that began Thursday night has yet to completely clear the area, preliminary 24-hour totals (as of 1 p.m. PST) have been very impressive but not close to record-breaking and about what one normally sees a few times every normal winter when major storms occur. Some peak 24-hour amounts include:

7.26” at Honeydew in Humboldt County. Honeydew is often cited as the wettest weather station in California with an average of 104.18” annually (actually per rain year of July 1-June 30). 7” of precipitation in 24 hours is a fairly common event at this location. Honeydew’s record calendar day rainfall is around 15.00” set on December 21, 1964 (that amount actually measured at nearby Ettersberg).

8.08” at Venado in Sonoma County. This is normally the wettest location in the North San Francisco Bay counties of Marin, Sonoma, and Napa and is not a notable amount for the location. The greatest calendar day rainfall on record for Sonoma County is 18.02” at Fort Ross on November 11, 1874.

7.32” at Mt. Umunhum in Santa Cruz County. Ben Lomond and Boulder Creek are normally the wettest locations in the Santa Cruz Mountains but they picked up only 4-5” in the past 24 hours. These are common big-storm totals. Just last March Ben Lomond picked up 17” of precipitation during a 3-day event. The town’s calendar day record is 15.20” on January 4, 1982.

8.15” at Mining Ridge in San Benito County (Big Sur region). This is usually the wettest location during storms that affect the Big Sur coastal mountains south of Monterrey. It is a relatively new station located at about 4000’ on a ridge overlooking the ocean. One storm last winter dropped 16” of rain in 24 hours here.

7.16” at Brady Creek in the Shasta, Trinity, and Siskiyou County region. The greatest calendar day rainfall on record in this area was 15.34” at Lakeshore on December 20, 1955.

7.32” at Bucks Lake in the northern Sierra foothills. This is not impressive compared to the records but the storm is still on going in this area as I write this.

In the cities at low elevations the rainfall has been relatively modest the past 24 hours:

1.26” San Francisco (downtown) and 1.77” at the normally drier airport location.

3.26” in Santa Rosa.

1.06” in Sacramento (International Airport location).

Wind gusts have been typical for a strong winter storm: 54 mph at San Francisco Airport. 67 mph on Mt. Diablo Peak (elevation 4,000’).

Snow is only just now picking up high in the Sierra Nevada but significant snowfall so far has been confined to very high elevations given the warm nature of the storm. In fact, San Francisco Airport recorded a low of just 61° last night (Thursday night) its 2nd warmest night of the entire year (the low on October 2nd was 62°).

I will post a blog storm summary next Monday when the last storm has passed. Meantime, the sun just broke out and it is turning into a balmy summer-like day here in Oakland!

Christopher C. Burt
Weather Historian