The former Techniques Development Laboratory (TDL) of the U.S. National Weather Service began collecting Manually-Digitized Radar (MDR) data in November 1973 from teletype reports. The MDR data were then archived in Model Output Statistics (MOS) predictand tape format to be used for thunderstorm prediction. The data were intended for both general and severe thunderstorm prediction using MOS which related the radar data to large-scale predictors from operational numerical models. Other uses of the data included development of improved initial moisture fields in TDL numerical models and verification of convective weather forecasts.

The MDR data were archived for a pseudo-grid covering roughly the eastern two-thirds of the United States. This pseudo-grid was a subset of the 47 by 51 (octagonal) polar-stereographic grid that was used for numerical weather output at the time.