Extreme Storm Predictions for the West Coast
From Chapter 9 of the Fourth National Climate Assessment.
It is predicted that there will be an increase in tropical cyclones in the Eastern North Pacific.
Atmospheric Rivers (ARs) from the Western sub-tropical Pacific are narrow atmospheric flows of high water content, which provide 30-40% of the precipitation in the West Coast states, and that fraction of the snowpack in the Sierra Nevada. “ARs are critical to ending drought in West Coast states”.
They will be more frequent and more intense in the future. By the year 2100, in RCP 8.5 projections, AR days will increase from 50% to 600%. They will have greater intensity because they can carry more water or have an increased specific humidity in a warmer atmosphere. They may shift poleward by a few degrees of latitude from southern North America.
Extreme events above 95% will increase 30-40% also.
