MAMMATUS Clouds over Gibsonia, PA  June 26th 1998

Maybe you recall this Friday evening when many in the Pittsburgh, 

Wheeling, and Steubenville areas were treated to this rare and 

startling sight of a skyful of MAMMATUS clouds at sunset. The 

following photos were taken by George Mikulan, retired WFO Pittsburgh

Lead Forecaster, looking south from Gibsonia Pennsylvania between 8 

and 9 pm June 26th 1998. 

MAMMATUS clouds are typically associated with strong thunderstorms

(cumulonimbus clouds) and very turbulent conditions. When Mammatus 

appear at levels below 10,000 feet, hanging below the base of 

cumulonimbus, meteorologists worry about tornados forming. However,

the Mammatus of June 26th were likely above 20,000 feet, and so were

likely outgrowths from the anvil tops of distant energetic 

thunderstorms to the south that evening. Cloud names come from Latin.

Mammatus refers to the clouds' rolling shape which remind some of 

cow's udders or breasts. Cumulonimbus comes from two Latin words: 

Cumulus meaning "heaping piles" and Nimbus meaning "giving rain".

Photos courtesy of George A. Mikulan, Gibsonia PA