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Weekly Weather Event -Week of Jan. 6

January 8, 2020

This piece is a continuation of coverage of the ongoing Australia fires. Readers are advised to check up to date sources as this event progresses.

One of the consequences of the Australia bushfires have been the presences of pyrocumulus and pyrocumulonimbus clouds, or cumulus clouds and thunderclouds that are formed by intense surface heat instead of solar radiation and other forms of atmospheric heating. These sources of heat can be either natural or man-made and range from wildfires, such as the bushfires currently plaguing southeast Australia, to volcanic eruptions.

Strong heat near the surface can intensify or create local updrafts, moving the hot air high into the atmosphere at rates comparable or stronger than the updrafts of supercell thunderstorms in the United States High Plains. Occasionally, these updrafts are strong enough to produce their own thunderstorms. Unlike a typical thunderstorm, however, these storms have comparatively little precipitation, making them hard to detect with aircraft radar.

Thunderstorms that develop from pyrocumulonimbus clouds can be a mixed blessing for firefighting efforts. These thunderstorms can bring much needed rain to dry areas, but they can also bring lightning strikes that ignite new fires or damaging severe weather such as flooding, hail, and damaging downdraft winds. High winds also run the risk of fueling and spreading the fires that are already present.