Intercomparisons of nowcasting techiques

A number of different nowcast systems have been used to analyze test cases of different varieties of weather systems in the Midwestern United States. An evaluation of TITAN (Dixon and Wiener 1993), WDSS-II, and S-PROG (Seed 2003) is performed on different case studies for selected Midwestern convective events as well as more widespread precipitation events. In addition, the UMBRELLA System (Fox and Wikle 2005) was run on the selected cases. This system features explicit representation of the uncertainty associated with the forecast generated. The selected cases cover a range of storm types. These include an initiation of an MCS over western Kansas on 15 June 2002, the Pierce City, MO tornado case from 4 May 2003 featuring storm splitting and merging, a bow echo case from the BAMEX experiment, and a pulse thunderstorm case.

High resolution MM5 simulations for the dynamic environment of the time periods given were performed on selected cases. An intercomparison of the nowcast systems was performed in order to identify potential strengths and weaknesses with respect to the dynamic nature of each of the storms. Statistics for each nowcast system will be presented showing that UMBRELLA, and its explicit handle on uncertainty, can be effectively used on uniform stratiform cases to complex convective situations.