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Roll cloud stuns locals near Qld/NSW border

Ben Domensino, Tuesday July 4, 2017 - 11:51 EST

A rare roll cloud was seen drifting over the Queensland and New South Wales border this morning.

The well defined tube-like cloud could be seen just to the north of Moree in NSW as the sun rose this morning, before moving east above Ashford and Goondiwindi. The formation had evolved into multiple, parallel lines by the tįme it reached Texas and Inglewood in the late morning.

Roll clouds, which are a type of arcus cloud, typically form when two air masses with different moisture content and density meet in an environment where a temperature inversion is in place. A temperature inversion simply refers to a parcel of warm air sitting above cold air near the ground, which most frequently occurs at night or early morning. Cloud forming where these two air masses meet is trapped under the inversion, forming a tube-like formation that travels along this invisible boundary as wave in the atmosphere.

This morning's roll cloud appears to have caused a noticeable change in wind direction and air temperature on the ground as it passed overhead. The wind direction at Moree abruptly shifted by about 180 degrees (from the NE to SW) and the temperature dropped by a degree as the cloud moved through at around 6:30am.

Roll clouds like this one are more common in northern Queensland, where the internationally renowned Morning Glory cloud can be witnessed during the buildup to northern Australia's wet season.

- Weatherzone

© Weatherzone 2017

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