Processes Influencing the Forecast Skill of the Synoptic-Scale Flow over the Arctic and of Arctic Cyclones

Research on synoptic-dynamic meteorology over the Arctic and on weather prediction over the Arctic is increasingly important given that the Arctic environment is rapidly changing and human activities in the Arctic are increasing. The purpose of this study is to increase understanding of processes influencing the forecast skill of the synoptic-scale flow over the Arctic and of Arctic cyclones (ACs). ACs are extratropical cyclones that originate within the Arctic or move into the Arctic from lower latitudes. Characteristics of the Arctic environment, and the characteristics and forecast skill of ACs, are compared between periods of low and high forecast skill of the synoptic-scale flow over the Arctic, which are hereafter referred to as low-skill periods and high-skill periods, respectively, during the summers of 2007–2017. The forecast skill of the synoptic-scale flow over the Arctic and the forecast skill of ACs are evaluated by utilizing the 11-member NOAA Global Ensemble Forecast System reforecast dataset version 2. Characteristics of the Arctic environment and characteristics of ACs are examined by utilizing the ERA-Interim dataset. There tends to be more vigorous baroclinic processes and latent heating over the Arctic, and in the vicinity of ACs, during low-skill periods compared to high-skill periods. There tends to be relatively large lower-tropospheric baroclinicity, lower-to-midtropospheric Eady growth rate, and latent heating in the vicinity of ACs during low-skill periods that are characterized by low forecast skill of intensity. The evolution of a selected AC during low-skill periods that is characterized by low forecast skill of intensity and that occurs in August 2016 is examined by utilizing the ERA5 dataset. The evolution of the selected AC appears to be influenced by baroclinic processes, latent heating, and interaction between the AC and a tropopause polar vortex.