With the sea-ice decline over the eastern part of the Eurasian Arctic (EEA), polar mesocyclones (MCs) and their most intensive representatives-polar lows (PLs)-can occur over more open-water areas. Visible and infrared MODIS images, active and passive microwave spaceborne instruments, and ERA Interim reanalysis data are combined and used to analyze the synoptic situations and to infer the factors influencingMC appearance and evolution over the Kara Sea, the Laptev Sea, the East Siberian Sea, and the Chukchi Sea. In recent years, the Arctic more often loses its summer sea-ice cover, and PLs may more commonly emerge within open-water Eastern Arctic regions during fall and summer months. This conclusion is derived basing on the analysis of more than 150 MCs for August, September, October, and November months over the EEA for the period of 2003-2015. PL and MC distribution and characteristics necessitate to be studied with a multisensor approach since neither reanalysis data nor data from a single instrument can provide sufficient means for their confident detection and analysis.