Heavy Rainfall Makes a Dent in California Drought
A surprisingly strong weather system brought the heaviest rainfalls seen since December 2012 to the San Francisco Bay Area on Tuesday-Wednesday and also soaked portions of southern California. High winds on Thursday night knocked out power to 67,000 in the Bay Area, mostly in Oakland where two wind-related deaths occurred.
In the San Francisco Bay Area, where the rainfall deficits have been the worst in the state so far this year, the rainstorm brought .75-1.75”, about three times what was forecast and the greatest storm total since December 20-21, 2012. Rainfall affected all of California although in the southern regions it was hit and miss. For instance in San Diego, Brown Airfield picked up only .04” (the site used in the tables below) whereas Lindbergh Field picked up .97”.
The rainfall broke a two-month long dry spell (last precipitation occurring at most locations on September 21st) and made a small dent in the year-to-date precipitation deficits which can be seen in the tables below:Precipitation totals and percentage of normal for the year 2013 through October 31st (top table) and through November 21st (bottom table).
In spite of the rainfall the state as a whole, and particularly central California (i.e. the San Francisco area), is still on track for its driest calendar year on record. San Francisco (downtown) will need an additional 3.80” between now and December 31st to avoid breaking its current driest calendar year total of 9.00” set in 1917. This is about what the normal precipitation for the city would be for the period of Nov. 22-Dec. 31, so is certainly possible if not likely.
A tight pressure gradient set up over central and northern California behind the storm on Thursday (November 21st) causing a damaging windstorm in the Sierra Mountains and the San Francisco Bay Area. Worst hit was Oakland where wind gusts in the foothills reached 65 mph Thursday night. Two people died in the city (falling tree branch and automobile accident) as a result of the high winds. 43,000 of the city’s residents lost power overnight (including myself) and an additional 24,000 in surrounding areas. The rainfall on Wednesday was particularly fortuitous given the high winds. With all the downed power lines and arcing of such that occurred, wild fires almost certainly would have been ignited otherwise. It was the most powerful windstorm in my neighborhood (Rockridge, Oakland) since I moved there in 2001.A very large tree was felled in downtown Oakland near the shores of Lake Merritt Thursday night. One of hundreds of such occurrences around the city.
Photo by Alex Olson.
In the Sierra Nevada winds were clocked gusting to 120 mph on Ward Mountain (8,525’) in the Alpine Meadows ski area. Other peak gusts included 90 mph 11 miles SSE of Cisco, 87 mph 7 miles NNE Mill Creek, 82 mph 5 miles NNW of Downieville, and 75 mph at Calaveras Big Tree.
Christopher C. Burt