Weather Whys; Atmospheric Stability

This is weather-wise. The stability of the atmosphere is an important factor in determining the likelihood of thunderstorms on any particular day. If parts of the atmosphere are unstable, storms are more likely to develop. The level of stability, however, is determined by the degree to which conditions in the atmosphere will change, if given the chance. To determine that degree of stability, scientists chart the progress of an imaginary mass of air that floats up from the Earth's surface. That mass is called an air parcel, which will rise when the air in it is warmer than the air surrounding it. The behavior of that parcel can tell scientists a lot about the current state of the atmosphere above them, and therefore about the likelihood of storms that day. For instance, if a scientist knows the atmosphere above his weather station is unstable, he might look for thunderstorm activity to develop. That's because the very processes which build many thunderstorms are aided greatly by

an unstable atmosphere. Now it's common for huge moist bubbles of warm air to rise from the ground on a spring or summer day. If the atmosphere is generally stable, those bubbles might only produce puffy, fair-weather, cumulus clouds. That's because a stable atmosphere can essentially put a lid on things and keep the clouds from growing too large. But in an unstable atmosphere, the bubbles may be able to create the huge thunderstorm cloud or cumula nimbus. The unstable atmosphere encourages the rise of the bubbles so they can more easily create the towering thunderhead. Weatherwise is a production of the Center for Analysis and Prediction of Storms at the University of Oklahoma, established in 1989 by the National Science Foundation for Research on Local and Regional Prediction of Storms. For Weatherwise, I'm Drew Barlow.