Better Atmospheric River Forecasts Are Giving Emergency Planners More Time to Prepare for Flooding

I was eating breakfast at Sears Fine Food in San Francisco on Monday and was watching the local weather forecast on a television screen. There was a happy looking sun for the rest of the day. Thursday had a threatening cloud with heavier drops, and Wednesday had a friendly looking cloud. I was aware that Thursday's conditions would be very rough. Satellite data and weather models showed that a major atmospheric river was likely to hit the city. The threat of the storm was not communicated in a way that was adequate.

There are rivers of water in the sky and they are pushed along by winds. The meteorological community officially defined them in the early 2010s after improved satellite imagery and science showed how these storms can form far out over the ocean. They can grow to 2000 miles long, 500 miles wide and two miles deep by the time they reach the western coast of the world. It takes 25 times the flow rate of the Mississippi River to bring an average rain or storm to those parts of the world.