Jeff Snyder
EF5
Most chasers I know use GRLevel3 for in-field, while-chasing radar data. That said, there are other competent choices (or, rather, at least one). Since the two main ones (GR and StormLab) offer free trials, I suggest downloading both and putting them through the paces. Personally, I'm a huge fan of GR, and GR software has a very good support community.