Trends in Skill of Daily Forecasts of Temperature and Precipitation, 1966–78

Abstract

Forecasts of minimum temperature and precipitation amount at Boston have been made and evaluated in the Department of Meteorology, MIT, in essentially the same format since 1966. These forecasts refer to the first through fourth 24 h periods in advance and are partly categorical and partly probabilistic in form. The skill level in the consensus forecasts, relative to forecasts of the long-term mean, is slightly more than 50% for the first day and around 10% on the fourth, except for conditional quantitative precipitation forecasting, which is decidedly less skillful. Regression analysis shows, except for the first day, slight increases in the skill of these predictions, at a rate of about six-tenths of a percent per year. The skill of the guidance temperature forecasts of the National Meteorological Center has lagged the skill of the consensus forecasts by a decreasing amount from 1966 to 1972. The lag from 1972 to date has not changed significantly and varies between 10 and 30% of consensus skill, depending on range and season. The guidance for the conditional quantitative precipitation forecast is inferior to both consensus and the long-term median control forecasts.