Atmospheric rivers, as they are called, are narrow but long ribbons of condensed water vapor carried by the wind. When a particularly tempestuous one barrels into the Pacific Northwest or California from the Pacific Ocean, it can unleash rain, dump snow and swell rivers for days at a time.
An atmospheric river that streamed into the Oregon and Washington coasts in late January delivered heavy rainfall and wind gusts of 50 mph. Here in the Inland Northwest, we felt its effects as well, but with moderate rain showers and wind.
The Pineapple Express is famous for soaking the West Coast after zipping across the Pacific Ocean from near Hawaii, but there are many not-yet-named rivers in the sky. Our understanding of them is so rudimentary that the mystery of how they interact with air and sea to influence precipitation is still being unraveled.
That’s where Miss Piggy comes in – a federal research plane used by scientists to fly straight into atmospheric rivers. The P-3 aircraft, loaded with sophisticated meteorological instruments, collects data ranging from measured precipitation and cloud density to the size of vapor particles that make up each river.
With Miss Piggy able to cut through these powerful moisture plumes, researchers with the National Oceanic and Atmospheric Administration have determined that the amount of water vapor they carry is equivalent to more than 10 times the flow of water through the mouth of the Mississippi River.
That’s a lot of water, which is why data garnered by scientists will be so valuable. Not only can we better forecast heavy rain, snow and flash floods, we can also better plan for the region’s water supply. After all, the presence of a strong atmospheric river can help ease drought conditions while the absence of one can prolong such conditions.
Nic Loyd is a meteorologist with Washington State University’s AgWeatherNet. Linda Weiford is a WSU news writer and weather geek.