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of the clouds are very low. Tornadoes sometimes occur when this type of activity is present.The warm-front thunderstorm is caused when warm, moist, unstable air is forced aloft over a colder, denser shelf of retreating air. Warm-front thunderstorms are generally scattered; they are usually difficult to identify because other clouds obscure them
Dry lines are the boundary between two air masses of different moisture content and separate warm moist air from hot dry air. While the temperature may be different across the dry line, the main difference is the rapid decrease in moisture behind the dry line.
It is the lack of moisture, which allows the temperatures to occasionally be higher than ahead of the dry line. However, the result is the same as the warm moist air is lifted along the dry line forming thunderstorms. This is common over the plains in the spring and early summer.
Outflow boundaries are a result of the rush of cold air as a
Terrain
As air encounters a mountain it is forced up the slope of the terrain. Upslope thunderstorms are common in the Rocky Mountain west during the summer.
2.3 LIFE CYCLE OF THE CLOUD
The building block of all thunderstorms is the thunderstorm cell. The thunderstorm cell has a distinct life cycle that lasts about 30 minutes.
2.3.1 Single cell.
The life cycle of a single cell can be separated into three stages:
· Developing stage
· Mature stage
· Dissipating stage
2.3.1.1 DEVELOPING STAGE:
Every thunderstorm begins life as a cumulus cloud. The developing stage lasts 5 to 10 minutes. A cumulus cloud begins to grow vertically, perhaps to a height of 40,000 to 60,000 feet. The cloud starts growing upward, driven by the latent heat as water vapor condenses. Strong updrafts prevail throughout the cell and it rapidly builds up into a towering cumulonimbus cloud. The diameter of the cell is between 2 and 8 km. Temperatures within the cell are higher than temperatures at the same level in the surrounding air, intensifying still more the convective currents within the cell. There is usually no precipitation from the storm at this stage of its development since the water droplets and ice crystals are being carried upwards or are kept suspended by the strong updrafts.
2.3.1.2 MATURE STAGE:
The mature stage typically lasts between 25 and 30 minutes. During this stage downdrafts develop, and after some time strong updrafts can be found at the leading part and pronounced downdrafts at the rear part of the Cb. The development of downdrafts is a consequence of the
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