A
polar low is a small-scale, short-lived atmospheric
low pressure system (depression) that is found over the ocean areas poleward of the main
polar front in both the Northern and Southern Hemispheres. The systems usually have a horizontal length scale of less than and exist for no more than a couple of days. They are part of the larger class of
mesoscale weather systems. Polar lows can be difficult to detect using conventional weather reports and are a hazard to high-latitude operations, such as shipping and gas and
oil platforms. Polar lows have been referred to by many other terms, such as
polar mesoscale vortex,
Arctic hurricane,
Arctic low, and
cold air depression. Today the term is usually reserved for the more vigorous systems that have near-surface winds of at least 17 m/s (38 mph).