Polar Low
Polar Lows look very similar to Commas but usually occur in northern latitudes. They develop under more specific synoptic conditions when compared to the more general features of a Comma.
A Polar Low is a meso-scale cyclone which normally occurs during winter time far north from the main polar front. In a northerly flow cold arctic air pours out over relatively warm seawater. Polar Lows start to develop in small baroclinic zones resulting from old Occlusions or arctic fronts. Polar Lows are closely related to the Conceptual Model of a Comma. Both are mesoscale systems developing in cold polar or arctic air. Whilst both are induced by upper air disturbances such as PVA and Potential Vorticity, there are some distinct differences. Polar Lows only occur during wintertime (October until April) while Commas can exist during the whole year. Weather events associated with Polar Lows are more severe than those accompanying a Comma.