Tracking California's Rivers of Rain
New instruments are helping forecasters get ahead of the "pineapple express."
Sometimes referred to as the "pineapple express," these events occur when winds sweep tropical moisture into narrow filaments.
The filaments, which scientists call atmospheric rivers, hit land as a series of intense storms, one after another. In 2010 one particularly strong atmospheric river doused parts of California with up to 26 inches (660 millimeters) of rain and dumped up to 17 feet (5.2 meters) of snow in the mountains.
The latest one struck last week, dropping 15 inches (450 millimeters) of rain in parts of northern California—just as scientists were preparing to report on the new forecasting system in San Francisco, at the annual meeting of the American Geophysical Union (AGU).
Atmospheric rivers are concentrated bands of water vapor that form
