Thunderstorm

A thunderstorm is a convective weather phenomenon with cumulonimbus cloud, lightning and thunder, often with heavy rain or hail. It forms in unstable air with strong vertical motion and can bring severe turbulence, wind shear, icing and sudden changes in visibility. Thunderstorms are most hazardous in and near the cloud, especially during take-off and landing. Pilots should avoid them with a wide margin, check forecasts and radar information, and never try to fly through an active cell.