Central California Enters a Drought Period Unprecedented in its Weather History

Central California Enters a Drought Period Unprecedented in its Weather History

There are few sites in the U.S. (or, for that matter, the world) that have as long an unbroken period of record for precipitation measurements as the city of San Francisco. This official record extends back to November 1849. Today, January 15th, the city has now entered unchartered territory by surpassing 1916-1917 as the driest ‘wet season’ to date on record.



Map of soil moisture conditions across the U.S. as of January 13th. NOAA/NCDC.

Driest Water Years (July 1-June 30) in San Francisco history

As of January 15th, San Francisco has received a seasonal precipitation total of just 2.12”. Here is a list of the top ten driest water years (since 1849-1850) for the city:



Season to date precipitation for selected California cities

Below is a list of seasonal precipitation to date for selected California cities (arranged from north to south) with comparison to normal:



Sierra snow pack issues

The snow pack in the Sierra is currently averaging 15% of normal for this time of the year, the lowest on record. The graphics below illustrate the dire situation:



Satellite images comparing California from a year ago to today. Not only is the snow cover drastically less but also notice how brown the central valley ground cover is relative to the green of January 2013. Images from NOAA.



The graphs above show the water content of the snow pack for the northern Sierra (top), central Sierra (center) and southern Sierra (bottom). As can be seen, the snow pack water content is at its lowest on record for all three districts. Graphs from California Department of Water Resources.

What’s next?

The worst drought on record for California was that of 1975-1977. After two consecutive dry seasons, and with this season on track to become the driest on record, drought conditions could even end up worse than those of 1975-1977.

Some are surprised that an official ‘drought emergency’ has yet to be declared by Governor Brown (although he has indicated that such is likely by February 1st). One of the reasons for this is that “legally, drought means much more than no rain. It means the governor, by making the declaration of a drought emergency, may lift environmental protections that help our [SF] bay-estuary to allow water transfers to other parts of the state. A declaration doesn't create water or money. It may allow the governor to redirect certain funds, typically unspent water bond funds. Those dollars are scarce, however, with the last water bond in 2009…The question before the governor is this: Does it make economic sense to drop environmental protections to move around more water? The governor's Drought Task Force is meeting weekly but so far has made no recommendation.” (This was a quote from an editorial in the San Francisco Chronicle newspaper on January 13th).



A map of the current status of the water levels in the major state reservoirs. As can be seen the situation is worse in the northern two-thirds of the state than in the southern section. California Department of Water Resources.

A major drought in California would have nation-wide implications. California is the number one state in cash farm receipts with 11.3 percent of the U.S. total. The state accounts for 15 percent of national receipts for crops and 7.1 percent of the U.S. revenue for livestock and livestock products. California’s agricultural abundance includes more than 400 commodities. The state produces nearly half of U.S.-grown fruits, nuts and vegetables. Across the nation, U.S. consumers regularly purchase several crops produced solely in California. The state is also the nation's largest agricultural exporter. –REF: California Department of Food and Agriculture

Needless to say, all agricultural crops and livestock are dependent on a reliable and continuous water supply.

Since the rainy season in this part of the country can be extremely variable, many are assuming that the drought is bound to break soon. The area is only at the halfway point in the water season, so not to worry too much yet. However, the forecast models are so dire (for lack of any precipitation until at least February) that one might think they must be erroneous. We shall see what verifies in the weeks ahead.

P.S.-Just In: San Francisco Airport observed its warmest January day on record today, January 15th, with a 73° reading. This beats the previous monthly record of 72° set twice before (on January 13, 2009 and January 24, 1948). Records at the airport location began in 1938. Oakland Airport reached 77° and Monterey hit a stunning 83°, which would be a record for even many summer days.

Christopher C. Burt
Weather Historian