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Record Dry Year Continues in California

By: Christopher C. Burt, 7:52 PM GMT on October 24, 2013

Record Dry Year Continues in California

California is enduring its driest calendar year on record as October draws to a close with no significant precipitation on the horizon for the rest of the month. San Francisco (airport location) has picked up just 2.12” of rainfall since January 1st, almost as dry as Death Valley where 1.71” has been measured so far this year. The last significant rainstorm to hit San Francisco was on December 25-26, 2012 when 1.10" was measured at the airport.





NOAA’s precipitation ranking by state (top) and by division (bottom) for January-September 2013. Since there has been virtually no rainfall in California so far this October, the California situation is not likely to look much different when the January-October versions are released in mid-November. NESDIS/NOAA maps.

The downtown San Francisco site (where precipitation records began in 1850) has picked up only 3.94” of precipitation since January 1st, by far its driest such period on record, the previous such being 5.72” in 1976. Normal precipitation for the January 1-October 31 period is 15.93”, so they are running at just 25% of normal. The driest full calendar year on record was 9.00” in 1917.

Although the San Francisco Bay area has been the most anomalously dry region in California (so far this year), all of the state has been exceptionally dry. Assuming no additional rainfall occurs over the next week (as currently forecast) here is a table of where some key sites sit precipitation-wise:



January through October precipitation totals so far this year compared to normal for the period. Death Valley received .75" in July, tying its wettest July on record with 1954 (records began in 1911). This is in sync with what was a very wet summer monsoon for the desert Southwest region.

Why not to worry (yet)

With the rainy season approaching heavy precipitation would be normal for November and December so it is much too early to speculate if 2013 will go down as the driest calendar year on record for the state or any individual locations. Also, it should be emphasized that California does not actually consider calendar year precipitation as that significant. It is seasonal (or water year) precipitation, which runs from July 1-June 30, that matters. For the past water season of 2012-2013 conditions were not so dire since heavy, above normal precipitation occurred in November and December of 2012.



Map a tables of California precipitation for the water year of 2012-2013 (July 1, 2012-June 30, 2013) and also or 2011-2012. Heavy rains and snow in November and December 2012 prevented the season from approaching near-record dry levels and the state’s reservoirs are filled to near normal capacity for this time of the year. Map and tables from Jan Null, Golden Gate Weather Services, San Francisco.

KUDOS: Jan Null of Golden Gate Weather Services for much of the above information.

Christopher C. Burt
Weather Historian

Extreme Weather Precipitation Records Drought

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

"San Francisco (airport location) has picked up just 2.12%u201D of rainfall since January 1st ... "

Ow.

Wikipedia has an article for "Water in California". Their water system has lots of moving parts, so to speak.
What about the foggy days in SFO area in the same period compared to the average ?
Can you put also a statistics of the hours of sunshine ?
I imagine that inland ,like in the Sacramento Valley, where fog is less common than on the coast, the number of hours of sunshine this year has been record-like.

It's odd to see California as red as it is in the top image, especially when it's surrounded by states that either just below normal (Nevada and Idaho), near normal (Oregon and Utah), and even above normal (Arizona and Washington). One would think such a prolonged drought would be more regional in scope. And for San Francisco's YTD rainfall to be just 124% of Death Valley's when it's normally 757% at this point in the year is truly remarkable.

These are interesting times indeed...
Quoting 2. maxcrc:
What about the foggy days in SFO area in the same period compared to the average ?
Can you put also a statistics of the hours of sunshine ?
I imagine that inland ,like in the Sacramento Valley, where fog is less common than on the coast, the number of hours of sunshine this year has been record-like.



What's weird is that no, at least just anecdotally; we actually had a strangely cloudy summer in the valley. Monsoonal stuff kept making it into the valley from SE -- not heaps of rain (though certainly more than is normal here in summer, we usually don't see rain May-Oct) but strangely humid and much more frequently cloudy than I've been used to over the past ~30 years.

It has been the year of weird blocking stuff and cutoff lows just sitting around off the west coast. One right after another, really.

Fingers crossed for a good, rainy (not flooding, ha) winter this year, because I cannot imagine the scale of drought problems we'll have if it's as dry as last winter. This year was only remotely ok because the reservoirs were in pretty decent shape.
Quoting 2. maxcrc:
What about the foggy days in SFO area in the same period compared to the average ?
Can you put also a statistics of the hours of sunshine ?
I imagine that inland ,like in the Sacramento Valley, where fog is less common than on the coast, the number of hours of sunshine this year has been record-like.



In addition, the central valley is frequently socked in with tule fog during January and February, and this year we had tule fog even later in the year.
I had no idea San Francisco has been so dry this year! Any greesnspaces in the bay area must be tinder dry.

Hopefully some good winter storms will help out in November and December.

Is Los Angeles' record for the driest year also under threat?
Quoting 6. BaltimoreBrian:
I had no idea San Francisco has been so dry this year! Any greesnspaces in the bay area must be tinder dry.

Hopefully some good winter storms will help out in November and December.

Is Los Angeles' record for the driest year also under threat?


I can't speak to the rainfall down that way -- I think they got some storms this spring/summer that we missed farther north -- but the thing with CA is that the actual water supply always depends really on the snowpack, the reservoirs, that sort of thing. With the exception of the north coast area, most of the state has to rely on some kind of storage to get through late spring into fall, since nearly no rain falls here during that time -- almost all of our rainfall in most of the state is winter into early spring, and the Sierra snows feed the rivers we draw from through the summer of virtually no precip (again, excepting the north coast, which is more like oregon in some ways.)

Snowpack this last season was something like 18% of normal, not much rain for the lower elevation reservoirs, either. If the year before hadn't stocked us up pretty well, we'd have been well and truly screwed.

I can't express how much we need this winter to give us some steadier water, and that's not about any particular locale's rainfall nearly so much as it's about whatever -- rain and snow farther off from the cities -- that gets our population _and_ our huge ag industry through the dry summer.
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