Structure
Polar lows can have a wide range of cloud signatures in satellite imagery, but two broad categories of cloud forms have been identified. The first is the "spiraliform" signature consisting of a number of cloud bands wrapped around the centre of the low. Some polar lows have the appearance in satellite imagery of tropical cyclones, with deep thunderstorm clouds surrounding a cloud-free ‘eye’, which has given rise to the use of the term "Arctic hurricane" to describe some of the more active lows. These systems are more common deep within the polar air. The second is a "comma-shaped" signature that is found more frequently with systems closer to the polar front.
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