The National Weather Service forecast for Friday to Sunday opens with:
THE ONSLAUGHT OF PACIFIC MOISTURE WILL CONTINUE TO BOMBARD MUCH OF THE WEST COAST
Who needs aliens — or even North Koreans — when you have computer-enhanced atmospheric energy waves!
Meteorologists use the term “atmospheric river” to describe a long, narrow plume piping deep moisture from the tropics into the mid-latitudes. One type of atmospheric river you may have heard of is the “Pineapple Express”, a pronounced plume tapping moisture from the Hawaiian Islands to the U.S. West Coast. Amazingly, according to NOAA’s Earth System Research Laboratory (ESRL), a strong atmospheric river can transport as water vapor up to 15 times the average flow of liquid water at the mouth of the Mississippi River! Suffice to say, if an atmospheric river stalls over a particular area, significant flooding can be the result.
Right now the immediate forecast suggests local challenges but nothing catastrophic. For those outside the Pacific northwest: mostly guilt-free storm porn. But just as one man’s porn may be another’s sex education (I too was once a thirteen-year-old boy), what unfolds this weekend could — even should — influence our expectations.
In early 2011 the US Geological Survey, CALEMA, and others conducted a multi-hazard demonstration project they called ARkStorm:
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 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…
As we saw with Sandy and Katrina and the Tohoku Quake and Mississippi flooding and profound drought in the Great Plains (and more) this is not a wild-eyed Mayan prediction of the future. This is merely the projection onto the present of a previous and recurring natural event.