It's really strange how extreme droughts brought on the last Ark Storm in California in 1862

 I'm not sure all of the Arkstorms that hit California and the western states were preceded by extreme droughts but it is also possible that is what occurred before too. But, historically there was a really bad drought before the 1862 floods in the western STates too. So, any time you have an extreme drought that we are presently witnessing it could be that the mechanisms could be set up for Atmospheric Rivers to drench the Western STates like they did in 1862 and historically every 150 to 500 years for thousands and thousands of years already.

As I have said before it is my present belief that the reason there were no cities when the Spanish first came to California was because any that existed were washed away thousands of years before. So, because of these periodic Ark Storms caused by Atmospheric rivers any cities people built from say China or Asia or people from the Hawaiian Islands or Russians or Native Alaskans historically likely were ALL washed away previous to the Spanish Coming in the 1500s and 1600s to California and the western States then.