1) Major thanks to Charles Miller and Cody Kirkpatrick (Indiana University) for initial versions of the PP fortran code.

2) This pages uses Storm Prediction Center (SPC) preliminary storm reports to create a "practically perfect" hindcast of the event. For more details, see Hitchens et al. (2013,WAF). Due to unreasonably high probability values consistently being produced—too frequent probabilities higher than 45%—some adjustments were made to dampen the high probabilities, hence the term "modified" in the title.

3) Reports are mapped to the NCEP 212 grid (approx. 40-km horizontal grid spacing).

4) A Gaussian kernel with σ=0.75 is used to smooth the event probability space.

5) Maps update daily at 1300 UTC.

6) Due to temporal lags in LSR submission, each day will be re-compiled at 1300 UTC until the event is over 96 hours old. At that time, the final map will be stored in the 90-day running archive.

7) A full archive of data discussed in our BAMS paper is available here. 

8) Please direct any questions about this page to vgensini at niu dot edu