The U.S. West Coast Network of Atmospheric River Observatories: Tools for Improving Situational Awareness in Operational Forecasting

The NOAA Earth System Research Laboratory Physical Sciences Division (NOAA/ESRL/PSD) operates and maintains a network of atmospheric river observatories (AROs) along the U.S. West Coast stretching north to south from Forks, Washington, to Santa Barbara, California. Funding for the network was provided by the California Department of Water Resources and the U.S. Department of Energy. An ARO is a collection of instruments that measure key ingredients of atmospheric rivers (ARs), narrow regions of enhanced water vapor transport associated with many landfalling Pacific storms. At each ARO site, a 449-MHz wind profiler with a Radio Acoustic Sounding System provides wind and temperature profiles from 180 m above the surface to 1-2 km for temperature and 6-8 km for winds, depending on environmental conditions. A Global Positioning System (GPS) receiver provides column-integrated water vapor. A 10-m tower provides surface meteorological measurements: temperature, pressure, relative humidity, wind speed and direction, solar radiation, net radiation, and precipitation accumulation. Scientists at PSD have used data collected by the AROs to develop tools to assist forecasters with warning the public about the impacts of ARs and other potentially hazardous weather. A wind profile comparison display allows forecasters to compare wind profile measurements with analyzed wind profiles in the operational High Resolution Rapid Refresh (HRRR) numerical weather prediction (NWP) model run by the NOAA National Centers for Environmental Prediction (NCEP). A water vapor flux tool allows forecasters to analyze and compare the wind, water vapor, and snow level (i.e., the level in the atmosphere where snow changes into rain) measurements with short-term predictions from the HRRR and the Rapid Update Cycle (RAP) NWP model run by NCEP. Users can also select the research versions of the HRRR and RAP models that are under development at the NOAA/ESRL Global Systems Division. A snow-level forecast verification tool allows forecasters to compare snow-level observations with the HRRR model at various initialization times and evaluates model performance over the past year to identify any potential model bias. These tools will be described and results of a study to evaluate model performance with the water vapor flux tool at several ARO locations will be presented.