Pineapple Express Animation, 2-7-17 (credit: NOAA & Scripps Institute of Oceanography)
A second atmospheric river (AR), often called a Pineapple Express, is about to return to the West Coast of the USA as a river of moisture approaches from the Pacific Ocean. The AR will bring added rain and snow to Callifornia that has been in extreme drought for nearly a decade. ~30-50% of California's annual precipitation occurs in from just a few of these weather events and contribute much to the State's snowpack and water supply. The first pulces of the new high-level, moisture system will begin hitting the coasts and mountains this week. The National Oceanic and Atmospheric Agency (NOAA) has developed an info-graphic that details the scientific characteristics of an atmospheric river:
The US Drought Monitor, a science collaboration between the Drought Mitigation Center at the University of Nebraska, the USDA, and NOAA that tracks national drought conditions and publishes a state and regional maps to show the situation at specific selected times. The latest map of California's drought summarizes the situation at the end of January 2017 and shows much of the state now in good condition in comparison to early spring, 2014.
California Drought Map Comparisons, May 2014 & January 2017 (credit: US Drought Monitor)
The new Pineapple Express now arriving could restore the remainder of the state to a good water conditions. Those dry swimming pools in LA will be back in use again but, hopefully, water conservation practices established statewide during the height of the drought will be maintained as dry weather will surely return again.