Verification of Toronto temperature and precipitation forecasts for the period 1960–1979 |
| |
| Authors: | A Stuart G Menger M Bredin J Capizzano D Cardish E Gately |
| |
| Institution: | 1. Program Development and Evaluation Branch , Atmospheric Environment Service , Downsview, Ontario;2. INTERA Environmental Consultants Ltd , Calgary, ALTA |
| |
| Abstract: | Abstract The accuracy of temperature and precipitation forecasts for Toronto was studied for the 20‐year period 1960–1979. Since any archive of official forecasts extends for only a small part of this period, it was necessary to retrieve the forecasts from newspaper records. The possible errors involved in such a data source were examined through a comparison of newspaper reported observations and the official record. On only a few occasions were significant differences observed. For temperature forecasts, the record indicates a significant loss of skill over the 20‐year periodin the prediction of maximum temperature for the first day. This was observed not only for the Bloor Street observing station for which the entire 20‐year record was analysed, but also for observing stations at Toronto Island, Downsview and Malton. The loss of skill over the years is greatest in winter when temperature is consistently predicted too low at all stations. For the entire period under study, precipitation forecasts consisted only of words and no quantitative information (such as probability of precipitation forecasts) was issued. Word choice is intended to carry information on the duration and expected spatial coverage of precipitation, but substantial inconsistencies between word choice and subsequent precipitation occurrence were found. Consequently, the verification procedure for these forecasts was very simple and ignored any differences implied in word choice. With this technique precipitation forecasts were shown to have improved over the 20‐year period. |
| |
| Keywords: | |
|
|
