The WSR-88D Rainfall Algorithm

TLDR

The Precipitation Processing System generates real‑time radar‑derived rainfall products to support the National Weather Service’s warning and forecast missions. This paper provides a detailed description of the operational WSR‑88D rainfall estimation algorithm. The algorithm converts reflectivity factor measurements into rainfall accumulations, incorporates rain gauge data, and applies quality‑control processing, with current deficiencies and future improvement plans discussed. The resulting rainfall products guide flood watch and warning issuance and serve as inputs for numerical hydrologic and atmospheric models.

Abstract

A detailed description of the operational WSR-88D rainfall estimation algorithm is presented. This algorithm, called the Precipitation Processing System, produces radar-derived rainfall products in real time for forecasters in support of the National Weather Service’s warning and forecast missions. It transforms reflectivity factor measurements into rainfall accumulations and incorporates rain gauge data to improve the radar estimates. The products are used as guidance to issue flood watches and warnings to the public and as input into numerical hydrologic and atmospheric models. The processing steps to quality control and compute the rainfall estimates are described, and the current deficiencies and future plans for improvement are discussed.