The new dual pol radar products are fascinating to use. Right now (3:26pm February 7th 2013) there is a changeover from rain to snow occurring across the Chicago area. Normally this is hard to pick up on ordinary reflectivity (right) but using a new dual pol product called the Correlation Coefficient (left), you can actually see the rain/snow line advancing on the city clear as day. Check out the animation below:
For those unfamiliar on just what this means. The product shows areas of uniform precip. The higher the values, the more uniform the precip is falling. So those areas of flat purple are either all rain or all snow (doesn’t matter what type of precip it is, as long as it is the same) and the areas of lower values (oranges/yellows/greens) are areas of mixed precip. In this case rain/snow/sleet.
The product is also useful in locating hail, and even debris during tornadoes.