CG Rate and CG Percent Positive Polarity

The CG rate algorithm counts the NLDN lighting strikes that have occurred within 10 km of the cell centroid since the previous radar volume scan, and divides by the time between scans to get a "strikes per minute" value. The 10 km radius limit was chosen to match the algorithm used in NSSL's WDSS cell table. The percent positive algorithm divides the number of positive polarity strikes by the total number of strikes (positive and negative). This is also recalculated every volume scan.