Cut-off low

[3][4] Whilst cut-off lows can form at any time of the year, they are more common in autumn, winter and spring in much of the areas affected, particularly in Australia and the Mediterranean Basin, when a mass of polar air is brought towards more southern regions (or northern, in the southern hemisphere) by the jet stream moving between 5 and 9 km altitude.

Composed of very cold air of polar origin, it typically has a horizontal extent of 300 to 1000 km and is 5,000 to 10,000 meters above sea level.

Cut off lows typically create unsettled weather and, in the warm season, they may produce a lot of thunderstorms.

A cut-off low has a slow movement, typically over a confined region, where it produces heavy rainfall, and can result in severe flooding.

In eastern Australia, a cut-off low can bring accumulating and widespread snowfall at low-level areas and as well as elevated regions in the subtropics.

Kona Low over Hawaii , an example of a cut-off low from the main core of the jet stream . [ 1 ]
A cut-off low situated over Italy and the tip of northern Libya.
Effects of a cut-off low of September 1997 in Alicante .