A Climatological Comparison of the Arctic Environment and Arctic Cyclones between Periods of Low and High Forecast Skill of the Synoptic-Scale Flow

The prediction of weather conditions in the Arctic is important to human activities in the Arctic. Arctic cyclones (ACs), which are extratropical cyclones that originate within the Arctic or move into the Arctic from lower latitudes, can be associated with hazardous weather conditions that may adversely affect human activities. The purpose of this study is to increase understanding of processes that influence the forecast skill of the synoptic-scale flow over the Arctic and of ACs. The 11-member NOAA Global Ensemble Forecast System (GEFS) reforecast dataset, version 2, is utilized to identify periods of low and high forecast skill of the synoptic-scale flow over the Arctic, hereinafter referred to as low-skill and high-skill periods, respectively, during the summers of 2007-17, and to evaluate the forecast skill of ACs during these respective periods. The ERA-Interim dataset is used to examine characteristics of the Arctic environment and characteristics of ACs during low-skill and high-skill periods. The Arctic environment tends to be characterized by more vigorous baroclinic processes and latent heating during low-skill periods relative to high-skill periods. ACs occur more frequently over much of the Arctic; tend to be stronger; and tend to be located in regions of larger lower-tropospheric baroclinicity, lower-to-midtropospheric Eady growth rate (EGR), and latent heating during low-skill periods relative to high-skill periods. ACs during low-skill periods that are characterized by low forecast skill of intensity tend to be relatively strong and tend to be located in regions of relatively large lower-tropospheric baroclinicity, lower-to-midtropospheric EGR, and latent heating.