Abstract
The production of interpretive weather element forecasts from dynamical model output variables is now an integral part of the centralized guidance systems of weather services throughout the world. The statistical forecasting system in the United States probably generates the most extensive suite of operational products, although other nations including Australia, Canada, France, Italy, The Netherlands, and the United Kingdom also routinely provide guidance for many weather elements and locations.
The United States' statistical guidance system has evolved throughout the past 20 yr. The two principal formulation methods that have been employed are the model output statistics (MOS) and “perfect prog” approaches. These techniques have advantages and disadvantages that influence both aggregate and specific day-to-day performance characteristics of the associated weather element forecasts. Verification results indicate that forecasts from both statistical approaches provide useful guidance for most weather elements and projections for locations throughout the contiguous United States and Alaska. The MOS forecasts have generally been superior to the perfect prog guidance; the drawback to MOS is the necessity to rely on a relatively stable numerical prediction model. As dynamical models change and increase in skill, the perfect prog approach may be preferred for some applications.
