Cyclone Development in Polar Air Streams over the Wintertime Continent

Abstract

A polar air stream cyclogenesis over the wintertime North American Continent is documented. Numerous similarities are found between this land case and oceanic polar lows studied Harrold and Browning (1969), Reed (1979) and Mullen (1979). The main difference between the land case and oceanic polar lows is that the land cyclone develops in an air mass with negligible water vapor content whereas oceanic ones clearly do not since they are characterized by enhanced cumulus activity during their early stage of development Hence, it is concluded that cumulus convection and its associated latent heat release are not essential for cyclone development in a polar air stream. It is also shown that the surface occlusion which forms from the merger of the polar trough with the main polar front does not follow the typical surface occlusion process as described by the Norwegian cyclone model.