Trends in Skill and Accuracy of National Weather Service Pop Forecasts

摘要

Ramage (1982) in his paper 'Have Precipitation Forecasts Improved.' analyzed 12 years of National Weather Service forecasts and concluded, 'After the contribution of relative precipitation frequency was removed, accuracy improvement, amounting to about 1% in seven years could be detected only in the eastern and central region winter forecasts.' This paper reports on a study undertaken to better understand Ramage's conclusions and to see whether they would hold over a longer period of record. This report is based not only on the 12 years of data used by Ramage but also on 4 additional years. The scores used are percent correct, Brier score, and skill score. There is only weak evidence of an improving trend in the 12-yr summer sample. However, there is strong evidence for an improving national trend in the 12-yr winter sample. Also, there is very strong evidence that the probability of precipitation forecasts improved over the longer period of record--1967-1982.