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 (see
), or arctic fronts (see
). 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 PV, there are some distinct differences.
In the mature phase Commas have a distinct tail, while Polar Lows have a more circular cloud pattern with sometimes even a
cloud free eye in the centre.
Polar Lows develop far away from the polar front while Comma clouds often develop much closer.
In contrast to Polar Lows, Comma clouds are often induced by shear vorticity originated from the polar jet.
Weather events associated with Polar Lows are more severe than those accompanying a Comma.
Polar Lows only occur during wintertime (October until April) while Commas can exist during the whole year.