Current aerobiological and forecasting models rely on differing schemes reflecting the effects of radiation on important processes. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model uses a simple cloud and radiative scheme with the option of using more complicated schemes when incorporated from outside meteorological data files such as those produced by the North American Model (NAM) or Nested Grid Model (NGM). Using the HYSPLIT program with data on Phakopsora pachyrhizi, evaluation of the radiation forecasting parameters inherent in the HYSPLIT model were performed. A set of parameters is presented to model spore extinction with irradiance under those UV-B radiation values inherent under different fractions of cloud cover.