Risk: As the Atmospheric River and Bomb Cyclone Pound the West Coast "The ARkStorm Scenario Could Flood California's Central Valley like a Bathtub and Cost $725 Billion"

 First up, from the Washington Post via MSN October 24:

Amid an exceptional drought that has wrought havoc on California for years, a Level 5 out of 5 atmospheric river is soaking the region, dumping double-digit rainfall totals and up to six feet of mountain snow. This heavy precipitation will help ease the drought but produce dangerous mudslides and debris flows in areas recently devastated by fires. 

The American GFS model simulates the moisture associated with an atmospheric river blasting into California on Sunday. (WeatherBell)

Atmospheric rivers are long, narrow swaths of exceptionally moist air, sometimes sourced from the tropics, that can produce excessive amounts of precipitation.

“It will be a wild 24 to 36 hours across northern California as we will see an extreme and possible historic atmospheric river push through the region,” wrote the National Weather Service in Sacramento, calling it a “dangerous, high-impact weather system.”

Flash flood watches are up for most of Central and Northern California, blanketing some of the same areas that went upward of six months without a stitch of measurable rain. Sacramento recorded its first 0.01 inches of rain last week since March 19, capping off a record-setting 222 days without precipitation. Now it is bracing for more than half a foot of rain and flooding. 

Through early evening local time Sunday, Sacramento had received more than 4 inches of rain, topping its Oct. 24 daily record. To its west, more than 6 inches of rain had fallen in Santa Rosa, where flash flooding was occurring.

Between 3 and 4 inches were reported in San Francisco and Oakland, which clocked wind gusts up to 60 mph. Around 160,000 customers were without power in California, mostly around the Bay Area due to the combination of wind and rain.

The drenching rain prompted flood advisories in much of the Bay Area, with numerous reports of high water.

Rainfall totals in Marin County just north of San Francisco had surpassed a foot in some areas.

The National Weather Service declared rare “high risk” of excessive rainfall for parts of Northern California, referring to the potential for “life-threatening flash floods and mudslides.” The threat is maximized over burn scars left by wildfires since 2018.

Strong, gusty winds will pervade even outside of thunderstorms, particularly in the mountains, where extreme snowfall is expected. Parts of the Sierra Nevada will measure snow by the foot, while wind gusts over 100 mph have been clocked on some peaks.....

....MUCH MORE

And why did we go to the Bezos blog for the story when we usually could not care less what they say except as an indicator of what story the D.C. powers-that-be-want told?

It is an homage to a line the Wapo's Joel Aschenbach wrote in 2008 (i.e. pre-Bezos ownership):

"...When in doubt, go with the most hysterical headline.

(Rule one of blogging is that the End Of The World will be good for page views.)"

-World War Five

He also tipped us to the US Geological Survey's ARKStorm Scenario in 2011

The ARkStorm Scenario Could Flood California's Central Valley like a Bathtub and Cost $725 Billion

From the U.S. Geological Survey:

The U.S. Geological Survey, Multi Hazards Demonstration Project (MHDP) uses hazards science to improve resiliency of communities to natural disasters including earthquakes, tsunamis, wildfires, landslides, floods and coastal erosion. The project engages emergency planners, businesses, universities, government agencies, and others in preparing for major natural disasters. The project also helps to set research goals and provides decision-making information for loss reduction and improved resiliency. The first public product of the MHDP was the ShakeOut Earthquake Scenario published in May 2008. This detailed depiction of a hypothetical magnitude 7.8 earthquake on the San Andreas Fault in southern California served as the centerpiece of the largest earthquake drill in United States history, involving over 5,000 emergency responders and the participation of over 5.5 million citizens.

This document summarizes the next major public project for MHDP, a winter storm scenario called ARkStorm (for Atmospheric River 1,000). Experts have designed a large, scientifically realistic meteorological event followed by an examination of the secondary hazards (for example, landslides and flooding), physical damages to the built environment, and social and economic consequences. The hypothetical storm depicted here would strike the U.S. West Coast and be similar to the intense California winter storms of 1861 and 1862 that left the central valley of California impassible. The storm is estimated to produce precipitation that in many places exceeds levels only experienced on average once every 500 to 1,000 years.

Extensive flooding results. In many cases flooding overwhelms the state’s flood-protection system, which is typically designed to resist 100- to 200-year runoffs. The Central Valley experiences hypothetical flooding 300 miles long and 20 or more miles wide. Serious flooding also occurs in Orange County, Los Angeles County, San Diego, the San Francisco Bay area, and other coastal communities. Windspeeds in some places reach 125 miles per hour, hurricane-force winds. Across wider areas of the state, winds reach 60 miles per hour. Hundreds of landslides damage roads, highways, and homes. Property damage exceeds $300 billion, most from flooding. Demand surge (an increase in labor rates and other repair costs after major natural disasters) could increase property losses by 20 percent. Agricultural losses and other costs to repair lifelines, dewater (drain) flooded islands, and repair damage from landslides, brings the total direct property loss to nearly $400 billion, of which $20 to $30 billion would be recoverable through public and commercial insurance. Power, water, sewer, and other lifelines experience damage that takes weeks or months to restore. Flooding evacuation could involve 1.5 million residents in the inland region and delta counties. Business interruption costs reach $325 billion in addition to the $400 billion property repair costs, meaning that an ARkStorm could cost on the order of $725 billion, which is nearly 3 times the loss deemed to be realistic by the ShakeOut authors for a severe southern California earthquake, an event with roughly the same annual occurrence probability....MUCH MORE, including three PDF's

HT:  the WaPo's Joel Achenbach* who, writing at Slate, says:
The Century of Disasters

Meltdowns. Floods. Tornadoes. Oil spills. Grid crashes. Why more and more things seem to be going wrong, and what we can do about it.

This will be the century of disasters.

In the same way that the 20^th century was the century of world wars, genocide, and grinding ideological conflict, the 21^st will be the century of natural disasters and technological crises and unholy combinations of the two. It'll be the century when the things that we count on to go right will, for whatever reason, go wrong.

Late last month, as the Mississippi River rose in what is destined to be the worst flood in decades, and as the residents of Alabama and other states rummaged through the debris of a historic tornado outbreak, physicists at a meeting in Anaheim, Calif., had a discussion about the dangers posed by the sun.

Solar flares, scientists believe, are a disaster waiting to happen. Thus one of the sessions at the American Physical Society's annual meeting was devoted to discussing the hazard of electromagnetic pulses (EMPs) caused by solar flares or terrorist attacks. Such pulses could fry transformers and knock out the electrical grid over much of the nation. Last year the Oak Ridge National Laboratory released a study saying the damage might take years to fix and cost trillions of dollars.

But maybe even that's not the disaster people should be worrying about....MORE

And some history:

In 1861 - '62 it rained for 45 days and the state capitol had to be temporarily relocated to San Francisco because Sacramento looked like this:

Leland Stanford went to his gubernatorial swearing-in in a rowboat just before everyone headed downriver to S.F.