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Australian fires and the weather

Bushfires generating their own thunderstorms.
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Posted at 4:29 PM, Jan 08, 2020
and last updated 2020-01-08 16:29:02-05

Bushfires have been burning across Australia since September. As of January 7th, 15.6 million acres have burned. (For comparison, Kentucky's total area is approximately 25.9 million acres.) The state of New South Wales as seen the worst fire conditions. 130 fires have burned as of Monday. Record-breaking temperatures, dry weather, prolonged severe drought, and strong winds have fueled these fires. Rain is providing some relief this week, but forecasters fear hot temperatures later in the week will enhance the fire risk.

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Smoke particles are often lofted into the stratosphere, which is the level of the atmosphere above where most of our weather happens. It can travel thousands of miles away from its source. The smoke from these bushfires has been detected on satellite imagery as far away as Argentina. Carbon monoxide has also been picked up by NASA satellites. The image above shows the average concentration of carbon monoxide at 18,000 feet. A large, highly concentrated plume is traveling across the Pacific Ocean toward South America.

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The smoke from the bushfires is also generating its "own weather" of sorts. Pyrocumulonimbus clouds, or fire-generated thunderstorms, are an indication that a fire is exhibiting extreme behavior. A non-atmospheric heat source, such as a wildfire or volcanic eruption, can locally create or enhance an updraft. The smoke plume rises and cools, then a cloud forms. The effect can be vigorous enough to produce its own thunderstorm.

The cloud can tower to altitudes over 50,000 feet. It is composed of ashy soot and water vapor. The vapor helps the cloud to grow. The pyrocumulonimbus cloud features comparatively little rain, making it tough to spot on radar. The clouds can produce abundant lightning and even severe weather, including heavy muddy rain, discolored hail, and damaging winds.

Pyrocumulonimbus

The most dangerous hazard of pyrocumulonimbus is when the updrafts become organized. This can lead to rapid fire growth and erratic behavior.