February 20, 2017

Today in Weather & Climate: California flood emergency edition (Monday, February 20th)

Hi all,

This is an urgent and important message, so I'll keep it short. If you're in a hurry, please read and retweet this message.

If you have family or friends in northern or central California—please get in touch with them on Monday morning, or sooner. The seriousness of the potential flood that is inbound on Monday and Tuesday cannot be overstated.
 
I just got off the phone with a NWS meteorologist at the Sacramento office, Bill Rasch, and he said they are increasingly concerned about the potential for the incoming atmospheric river to cause substantial or even historic flooding with little immediate notice. They are urging people to prepare to evacuate with less than 15 minutes warning, and expecting flooding in places that haven't flooded in "many years." As far as the this sort of dire wording, they have tentative plans to "take it up a notch" tomorrow—this is the real deal, a situation that likely hasn't hit California in decades, or maybe much longer.



Here's what is causing so much concern: If the atmospheric river stalls, there could be up to a foot of rain in a span of about 36 hours over places that are already flooding—that's a rainfall intensity that isn't expected more than once a century, or even more rare. At risk is the vast network of levees and dams and diversions that literally make modern California what it is, and protect hundreds of thousands of people. If this system is compromised, the scale of disaster would be among the worst in U.S. history. A dire 2011 New York Times magazine piece outlines the scenario. It's not pretty.

The implications of this flood would be huge: If the levee system is breached, Sacramento could have 30ft of flooding, and much of the state's water delivery system could be paralyzed by an influx of saltwater, including much of southern California. Two-thirds of people in the state could lose fresh water. That's not to mention the potential loss of life. Of course, this is not a given based on the latest weather forecast—but the fact that it can't be ruled out should cause everyone in the region to pay close attention.
 
This is something that should be wall-to-wall national coverage, but I haven't seen circulated much so far. Please help get the word out.
 
Thank you so much,
Eric

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