A mesoscale, real-time four-dimensional data assimilation and short-term forecasting system (RTFDDA) has been developed at NCAR. Built upon a high-resolution MM5, the RTFDDA system continuously assimilates available observations from various sources and provides updated 3-dimensional analyses and short-term forecasts in a quick cycling fashion. At present, the RTFDDA system is being adapted for real-time short term (1-12 h range) forecasting of snowbands.

Recently, real-time Level II radar observations in the Corridor Integrated Weather System (CIWS) domain have become available via the Collaborative Radar Acquisition Field Test (CRAFT) network. The domain has more than 20 radars, and covers an area of approximately 1500 km x 900 km. Three-dimensional mosaic reflectivity for the region, as well as radial velocity from the individual radars, are accessible in real-time. The objective of this work is to enhance the RTFDDA system by utilizing the CIWS radar observations.

In this work, feasibility of using the RTFDDA system and CIWS radar data for snowstorm forecasting is investigated. Techniques that can effectively assimilate Level II radar observations into MM5 are explored. Case studies are conducted for snowstorm events that occurred in northeastern U.S. The results are used to search for the optimal strategies for radar data assimilation in an operational setting.