Daily Archives: June 1, 2017

SoCal Rain Update: Almost a Wrap

First of all, I would like to apologize for single-handedly jinxing and ruining a banner water year for SoCal, with this closing paragraph to the last update:

The last 6 years are a reminder that for SoCal the faucet can turn on just as quickly as it turns off – and vice versa. The forecast for the next week or so is dry and in fact once, water year 1996-97, LA had no measurable rain between March 1 and the end of the water year. So now that I’ve sufficiently jinxed things, you’d better hope extra hard for some more drought relief this year!

While we managed to escape without nothing, all we have to show for March, April, and May is 0.49”, bringing the total for the water year 2016-17 to 18.99”. June through September, the end of the water year, has only brought more than 1” of rain 14 times out of 140 years of records, so let’s call this an almost wrap and see where this year stands.

Currently, downtown LA is at 18.99” of rain for the water year. This is about 4” greater than the yearly average, and well past any of the drought years. However, it’s a little short of the last good year, 2010-11. The strong El Niños of 1982-83 and 1997-98 have left us in the dust.


To put this year in context, here’s where it falls on a histogram of LA precipitation. Falling right into the 18”-20” bin, we can see that this year was indeed wetter than typical, but not a once-in-a-lifetime record breaker like northern California had.


The multi-year water trends show we are still in a multi-year precipitation drought condition, with the 5 and 6 year totals just barely above record lows. However, with WY 2011-12 (8.70”) and WY 2012-2013 (5.93”) falling out of the 6 and 5 year totals, respectively, for next year, hopefully those totals will continue to improve.


Looking at the distribution of LA rainfall, this year falls right around the 75th percentile. Again we can see that while this was a wet year, it was by no means into the rarefied territory up above about the 85th or 90th percentile. This was the 35th wettest year in LA, out of 140 on record. By comparison, the 4-year drought period 2012-2016 had three years in the driest 11 on record (2015-16 #11, 2013-14 #8, and 2012-13 #7).


Finally, we should note that while it is rare for southern California to get much rain between now and the end of the water year in September, it has happened 6 times. Most often this precipitation comes in September from tropical storm remnants, such as the 2.39” received in September 2015 from the remnants of Hurricane Linda. This improbable event alone bailed out water year 2014-15, which otherwise would have been only slightly better the rest of the 2011-16 drought years. Meanwhile, the only tropical storm to make landfall in California in the 20th century brought over 5” of rain in September 1939, causing severe flooding. So while this post is probably it for the year, there’s always a chance otherwise!