Cumulus cloud warnings

They have a record of extracting tin cans from the air and crushing them. Thunderstorms start when moist air continually rises because of heat energy from the ground and in the atmosphere. This is the reason thunderstorms are most prevalent during summer months. The rising air cools, and then falls, only to rise again with the already rising air. Eventually, the top of the storm condenses, and rain falls.

If storms rise high to the freezing level, ice forms. As the rising air falls and rises repeatedly inside the small columns of these storms, the ice particles get larger and fall to the ground as hail. The size of the hailstones is a reasonable measure of the storm’s intensity. Storms can reach heights of up to 10 miles while the bases are only a few miles wide.

The beginning of thunderstorm formation is called the developing stage, characterized by updrafts and formation of a cumulus cloud. The cumulus continues to grow higher, while assembling enormous amounts of moisture. When the storm matures, the tops fall back to the earth forming tremendous downdrafts, in which airplanes have no chance of escape. When the air reaches the ground, it goes out in all directions.

The outward rushing air is a sign of danger for pilots. Soon after the rush of outward air, pilots could find themselves in the downdraft column of air, called microburst. That would be “Houdini” time. The best way to avoid the dangers of thunderstorms is to avoid thunderstorms completely. No magic required.

Much of the science of thunderstorms was poorly understood until after several accidents caused by thunderstorms in the 1970s and 1980s, notably one in New York and one in Dallas. These cases prompted investigators to focus on avoiding dangerous weather, especially microbursts. After these accidents, sensors were installed at major airports to improve safety, and “microburst” was added to the aviation weather vocabulary.

In addition, the accidents brought to light a procedural problem, where pilots were responsible for all decisions regarding weather, while air traffic control was responsible for providing traffic information only. Airports would stay open as long as the visibility and height of clouds were suitable for approaches. This led pilots to fly into thunderstorms because they appeared as heavy rain. Since those accidents occurred, procedures have changed. A joint effort to provide a wider safety margin was instituted where ATC would prompt aircraft to hold outside the area of thunderstorms or proceed to an alternate airport. A safety margin was established that benefited everyone.

Ralph B. Bacchus is a retired CFI, CFII, and advanced ground instructor with thousands of hours of teaching in flight and in the classroom.