Examination and Modification of the New Atmospheric River Scale to Facilitate Investigation of Past Events as Well as the Forecasting of Impacts due to Future Events

It is apparent that there are differences between parameters such as time of year, antecedent conditions etc., that accompany the impacts associated with Atmospheric River (AR) events. One way to analyze past events and anticipate future impacts is via standardized anomalies, storm data and the MERRA-2 dataset. The use of these tools can result in guidance that smooths out some of the differences between County Warning Areas (CWAs) as opposed to absolute AR magnitudes, especially when a table is used to approximate impacts with general phrases. The manner in which the impacts evolve with the strength and duration of the AR also shows “uniqueness” between respective CWAs. In an effort to characterize this, our objective is to “tune” the WR Situational Awareness Anomaly Values information for IVT to make it more dynamic. This would allow factors such as time of year, antecedent conditions, burn scars, duration etc., to be considered. A prototype is proposed, in conjunction with what has already been done by National Weather Service Western Region Headquarters that changes anomaly criteria based on various factors, (for example, those mentioned above), in order to give potential impact information to forecasters and ultimately the end users as well.