Mammatus clouds
Appearance: Mammatus clouds are soft, pouchy formations which can resemble wool, bubble wrap or cow's udders
Occurrence: These clouds are found in mid-latitude and tropical climates including parts of Australia as a result of higher temperatures, increased moisture and strong atmospheric instability.
Conditions: In air that contains ice particles or water drops, evaporation cools the inside of the cloud creating negative buoyancy. Along with the weight of the particles, this causes it to puff down instead of up.
Location: Mammatus have been seen in many places, especially tornado-prone ones like the Midwestern United States. They are frequently found on the bottom of thunderstorm anvils and indicate large water droplets and heavy rain. A common misconception is they mean a tornado is coming.
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