The verification of WPC grids is based on point forecasts. WPC is not actually verifying the 5-km grids since we do not have access to a gridded verification field. Instead we are verifying the 449 WPC point forecasts that are used to produce the gridded forecasts. At each point, the forecast values are verified using observations at that point.

For comparison, we use a similar methodology to verify MOS forecasts and NDFD grids. MOS values at the 449 points are verified directly with observations. To verify the NDFD grids, WPC interpolates point forecasts from the NDFD to the same 449 points and compares them to the same observations used to verify MOS and WPC point forecasts.

If you have any questions about this verification process, please contact Edwin.Danaher@noaa.gov.