part of the equation
The SPC runs a comprehensive surface objective analysis scheme called SFCOA. The system runs at the top of each hour, using the latest 40km RAP forecast grids as a first guess. Next, the surface data is merged with the latest RAP forecast/analysis upper-air data to represent a 3-dimensional current objective analysis. Finally, each gridpoint is post-processed with a sounding analysis routine called NSHARP to calculate many technical diagnostic fields related to severe storms.