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California Drought Update: March 1st

By: Christopher C. Burt, 8:45 PM GMT on February 29, 2016

California Drought Update: March 1st

California’s rainy season is now a month past its mid-point (which would be around February 1st) and the drought prognosis is mixed: not as good as most hoped but it could be worse. A wet and snowy January has been followed by a very dry and very warm February (it was San Diego's warmest on record). March will hold the key as to how the season ends up. Herein is an end-of-February update on the status of reservoir, snowpack, and precipitation levels/amounts and how it compares to the last time I blogged on this subject six weeks ago January 7th.



The latest California Drought Monitor map (as of February 23rd) shows a modest improvement to the state’s overall drought situation since the rainy season began in earnest three months ago. Map NOAA, USDA et al.

Precipitation

As of the end of February seasonal precipitation (since July 1, 2015) is running about 80% of normal statewide with a general bias toward wetter conditions in the north versus drier conditions in the south (with the notable exceptions of San Diego—which received tremendous tropical storm-related rainfall in August and September-and Fresno which enjoyed its wettest January in 21 years). After a promising start to the rainy season in December and January, February fell flat and has finished as one of the driest such on record. In fact, February was so dry that it erased most of the precipitation and snowpack surplus that had developed earlier in the season. Below are two tables comparing seasonal precipitation for select cities as it stood on January 7th (the previous time I blogged on this subject) and February 28th. As one can see there has been a modest decline in precipitation percentages of normal across the board (and a very significant decline in Los Angeles and San Diego).





Season-to-date precipitation totals and normals for select California cities as of January 7, 2016 (top table) and as of February 28, 2016 (bottom table). The sites are arranged geographically from north (Eureka) to south (San Diego).

What has been most disappointing about this winter (so far) is how El Nino has generally under performed precipitation-wise in California. There have been plenty of Pacific storms that have raked the West Coast but the focus has been primarily on the Pacific Northwest. In fact, Seattle has experienced its wettest climatological winter (Dec-Feb) on record. If we look at the history of the past strong/very strong El Niño’s (since 1950) we can see that the precipitation’s geographical distribution has been unusual this El Nino season so far (for the November-February time period).



Oceanic El Nino Index since 1950. The seasons experiencing strong or very strong El Niño’s are highlighted in red and were those of 1957-1958, 1965-1966, 1972-1973, 1982-1983, 1997-1998, and 2015-2016. Graph courtesy of Jan Null, Golden Gate Weather Services.

Lets compare the November through February precipitation totals for each of those El Nino seasons in Seattle, San Francisco, and Los Angeles.



November-February precipitation totals for Seattle, San Francisco, and Los Angeles for each and all of the strong/very strong El Nino seasons since 1950. The anomaly of this season (2015-2016) is immediately apparent. This El Nino has seen Seattle with 157% of normal precipitation and Los Angles with 44%. In the previous five El Nino seasons Seattle observed an average of 97% of normal precipitation whereas Los Angeles saw 166% for the November-February time frame.

Here is another graphic that illustrates just how unusual this El Nino season has been for the Los Angles basin area so far this winter.



Percentage of normal to date 'water year' precipitation (which begins October 1st--'seasonal' precipitation year begins July 1st in California) for the Los Angles basin area during the past five strongest El Nino’s compared to this season. Graph courtesy of Zack Labe, Univ. of California-Irvine.

Reservoirs and Snowpack

As bad as the actual precipitation figures outlined above may look, the reality in the reservoirs and mountains is not so grim. For one thing most of the heaviest precipitation that has fallen so far this season has occurred in the far northern reaches of the state which is where the largest and most important reservoirs are located. If we compare the reservoir capacities as they stood on January 7th to where they are now (February 28th) we can see a major improvement in the levels at Shasta Reservoir and Lake Oroville, the two largest and most important water-holding facilities in the state.





California reservoir conditions as of January 7th (top map) and February 28th (bottom map). As one can see there has been a tremendous increase in the water levels at both sites over the past six weeks (from 51% of normal to date on Jan. 7 at Shasta to 83% now and from 47% normal Jan. 7 at Lake Oroville to 75% now). Maps provided by the California Department of Water Resources.





Snow water content for the northern, central, and southern sections of the Sierra Nevada and other mountain ranges as they stood on January 8th (top map) and February 29th (bottom map). Although it has fallen below average again (as of the end of February) it is, at least, close to normal and, compared to last year, a huge improvement. Maps from the California Department of Water Resources.



As can be seen above, the Sierra and Trinity Mountain snow packs have fallen below average (for the date) again statewide as of the end of February. On January 7th the statewide average snow/water equivalent stood at 107% of average at that time and now it is down to 85%. Although this is not great it also isn't so bad. Much of the lost snow pack melted during the mild February but much of the runoff flowed into the state's reservoirs (hence the reservoir's relatively healthy condition at this time). Furthermore, it is altogether possible to have additional tremendous snow accumulations in March and April.

In fact, on that upbeat note, current forecast models indicate a return to a wet, possibly very wet, pattern beginning around March 5-6 and continuing for at least two weeks (the GFS model is calling for 8"-10" of rain in San Francisco between March 5th-16th, we shall see!). The storms should affect the entire state, including at last, the bone dry south. How cold the storms might be, and thus how much snow for the Sierra might accumulate, has yet to be determined.

Christopher C. Burt
Weather Historian

Extreme Weather El Nino 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

Thanks for the comprehensive update, Christopher.
Hoping for a March Miracle like 1991. This week's pattern is a start.
Grammar tip: When making a regular noun plural (El Nino ---> El Ninos) it is not necessary to use an apostrophe. Apostrophes are only used to mark omissions and possessives of nouns; (It will ---> It'll, They are ---> they're) and (El Nino's power can be great). Love your blog!
A bit concerning that even with a very powerful el nino, the totals are still lacking. Next year should be interesting should we have a lesser el nino and back to drought conditions. Funs certainly not over yet.
Quoting 4. Brett70:

Grammar tip: When making a regular noun plural (El Nino ---> El Ninos) it is not necessary to use an apostrophe. Apostrophes are only used to mark omissions and possessives of nouns; (It will ---> It'll, They are ---> they're) and (El Nino's power can be great). Love your blog!


Grammar tip for "grammar trip". "not necessary" implies it is correct but not preferred. I believe what you want to say is "incorrect" rather than "not necessary"

Exiting 120 year old English teacher mode:-)

And readers note, there is 10X more value in the original tip than in my minor modification of it.
NASA: Tracking California Rains During El Niño

Off topic but..

It would be interesting if you would compile a list of all of the different times and locations that PWAT records for month, season, or period of record have been broken in the past year in the U.S. Here in DC it's already happened twice, once in August and once in December with another at least close shave in late February. Both the December and February
incidents were accompanied by summer intensity convective rainfall rates and flash flooding.
Quoting 7. BaltimoreBrian:

NASA: Tracking California Rains During El Niño


Did you mean

?
They seem to be the same video, LowerCal---I put up the one I found on NASA's Goddard youtube page.
California is a naturally dry part of North America and to call it "drought ridden" would be a misnomer, not accurate. I think what is normal for California is "dry" not wet.
The rain will help.
Science can now link climate change with some extreme weather events

phys.org

"In the past, many scientists have been cautious of attributing specific extreme weather events to climate change. People frequently ask questions such as, 'Did climate change cause Hurricane Sandy?' Science can't answer that because there are so many relevant factors for hurricanes. What this report is saying is that we can attribute an increased magnitude or frequency of some extreme weather events to climate change," said David Titley, professor of practice in Penn State's Department of Meteorology and founding director of Penn State's Center for Solutions to Weather and Climate Risk, who chaired the committee that wrote the report.

The committee found that scientists can now confidently attribute some heat waves and cold events, and to a lesser degree droughts and extreme rainfall, to human-caused climate change. Even a decade ago, many scientists argued that research could not confidently tie any specific weather events to climate change, which the committee reports today is no longer true today
Quoting 10. BaltimoreBrian:

They seem to be the same video, LowerCal---I put up the one I found on NASA's Goddard youtube page.
I figured they were but for me (Firefox 45.0 on ubuntu 15.10) in your comment it only shows up as a text title not a link or video.
Quoting 10. BaltimoreBrian:

They seem to be the same video, LowerCal---I put up the one I found on NASA's Goddard youtube page.
Brian, the way you have been posting youtube videos recently they show up in Windows 10 with the Edge browser or Firefox. The youtube videos do not show up in Ubuntu Linux unless they are "coderized".
Thank you! What a thorough report. I need look nowhere else. PS - When is your next update?
I plan an update on the California drought situation to be posted on March 31 or April 1. Thanks for your interest.

Quoting 16. davescz:

Thank you! What a thorough report. I need look nowhere else. PS - When is your next update?
"Drought" is a misnomer for California. It's just a dryer landscape of North America which is normal.
A drought is a period of below-average precipitation within a given region.
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