Weather Encyclopedia

Air Mass Thunderstorms

The three-stage thunderstorm cycle, cumulus, mature and dissipating, is typical of single cell thunderstorms that regularly develop late in the afternoon and in the early evening on warm, humid days.

An air mass generated thunderstorm is typically associated with a warm, moist air mass that is in place over a region. Factors that can help trigger the development include such things as a pocket of cold air aloft or the presence of a mountain or sea breeze.

This type of thunderstorm typically produces brief periods of heavy rain accompanied by thunder and lightning. When these common thunderstorms occur, you might find yourself in a downpour, while on the other side of town, friends are basking in the sun, totally unaffected by the inclement weather. This type of thunderstorm activity is common in many parts of the United States during the summer months.

A thunderstorm associated with a tropical air mass generally does not last longer than an hour and tends to be less severe than thunderstorms associated with fronts. These storms generally bring refreshing precipitation to gardens and crops and temporary relief from the heat on a warm, humid day.

Thunderstorms forming in tropical air masses are especially common in Florida. The Florida peninsula experiences more thunderstorms per year than any other location in the United States.

The northern half of the United States can experience air mass type thunderstorms during the summer months when tropical air is more likely to be in place. However, because this area of the country is closer to the summer location of the jet stream, many summer thunderstorms in the northern US latitudes are caused by the invasion of cold fronts into a warm air mass.

The usually arid Southwest primarily encounters thunderstorm activity when tropical air flows into the area around high pressure systems.

This type of weather pattern generally causes the Southwestern monsoon season that regularly occurs during the months of July and August in Arizona, New Mexico, southern Colorado, Utah, southern Nevada and occasionally in the California desert.

Because the air flow off the Pacific Ocean is moist and cool, tropical air mass type thunderstorms are rare in both California (particularly west of the southern mountain ranges of the state) and along the entire West Coast.