Forty Years of NWS Forecasts: Past Performance and Future Advances

The Meteorological Development Laboratory (MDL) of the National Weather Service (NWS) has issued model output statistics (MOS) guidance forecasts for nearly four decades. For many years, MOS guidance was generated for observing stations and formatted in text bulletins while official NWS forecasts for stations and zones were created by forecasters typing text. Today, the National Digital Forecast Database (NDFD) contains official NWS forecasts produced by forecasters at local Weather Forecast Offices (WFOs) and national centers on a fine-resolution grid. MDL also issues gridded MOS guidance in support of NDFD. Recently, MDL has applied the MOS approach to the European Centre for Medium-Range Weather Forecasts (ECMWF) model to generate additional station-based guidance.

The NWS and MDL routinely evaluate official forecasts at stations and compare the skill of the human forecast to the guidance for the same weather element. Improvements in NWS public weather forecasts and in statistically post-processed numerical weather prediction (NWP) can be traced by the verification of the weather element guidance.

In this paper, we examine the skill at stations of four decades of official NWS maximum temperature, minimum temperature, and 12-h probability of precipitation forecasts compared to MOS guidance for forecast periods out to approximately 60 hours in advance. The skill of the forecast and guidance has increased significantly since the late 1960s and early 1970s. We also investigate the performance of the last two years of NDFD, Global Forecast System-based MOS (GFS MOS), and ECMWF MOS forecasts for forecast periods out to seven days in advance.