The software was upgraded in 1993 to take advantage of the higher resolution rainfall estimates from the WSR-88D radar. Figure 1 shows the an example of these MAP areas. Since the response time of major streams is relatively slow, flood warnings, rather than flash flood warnings, are typically issued for the larger streams. Example of MAP areas. Stream subdivisions are smaller tributaries contained within primary streams or other stream subdivisions.
Urban areas can experience dangerous flash flooding when storm sewers back up from intense rainfall.
Many of these urban areas are not directly impacted by stream flooding. Rainfall accumulations are computed from successive DHR products, following as closely as possible the current Precipitation Rate and Precipitation Accumulation algorithms. However, data are output at 1 km resolution, instead of the 2 km data associated with the current Precipitation Rate algorithm. The computed ABR values represent an area weighted average accumulation of all radar rainfall estimates in a watershed, including zero accumulations. Figure 2 shows an example of basins for each of the basin sizes.