Thunderstorms are generally classified as either an air mass thunderstorm or a frontal thunderstorm. Thunderstorms may be further classified based on their trigger (lifting mechanism) which may be due to frontal activity, geography or the heating of the earth’s surface.
An air mass thunderstorm is generally a thunderstorm not associated with a front or other type of synoptic-scale forcing mechanism. Rather, air mass thunderstorms are associated with warm, moist and unstable air masses in the summer months, hence the name. They develop locally during the afternoon or late in the day in response to convective heating from the surface. Typically they do not persist very long, form in isolated cells and dissipate rather quickly after sunset.
As previously mentioned thunderstorms are categorized based on their lifting mechanism. The following are types of air mass thunderstorms and although each presents the same threat to aviation safety all have a different initial lifting mechanism.
Frontal thunderstorms develop at the boundary (front) between two different masses of air, so they are less dependent on the season of the year than air mass thunderstorms. The movements of air masses that cause thunderstorms are mainly found at cold fronts. The denser cold air pushes under the warmer air and lifts it upwards. Thunderstorms associated with a cold front are typically more severe than those associated with a warm front as the cold air tends to lift the warmer air to greater heights. Frontal thunderstorms typically form along a continuous line.