The Presentation of Precipitation Information in Television Broadcasts: What is Normal?

In a typical weather broadcast, observed precipitation information such as the daily amount that fell and the accumulated monthly total are shown and compared to the mean monthly average or “normal” precipitation. Such information, however, may not adequately describe whether or not that particular month is fairly typical for the time of year or truly an unusual occurrence. Here it is shown that monthly average precipitation may not be representative of the typical value for a particular month at all. Thus it is suggested that the presentation of precipitation information can be augmented with elementary statistical information in order to give a more meaningful presentation of precipitation information without the need to explain the basis of such statistical information. A study of the climatological behavior of monthly precipitation values over a 118-year period for Columbia, Missouri is performed in order to provide the rationale for displaying "typical" precipitation ranges