Thunderstorm Causes
| Three conditions are necessary to create a thunderstorm: | 1. Instable Air
2. Some Type of Lifting Action 3. A Relatively High Moisture Content |
life cycle:
|
1. Cumulus: |
A lifting action initiates the vertical movement of air. As the air rises, it cools to its dewpoint and the vapor condenses into water droplets. Heat released by the condensing vapor provides energy for the vertical growth of the cloud. Strong updrafts prevent precipitation from falling, instead they rise and fall inside the cloud, growing larger. Updrafts as great as 3000 f.p.m. may begin near the surface and extend well above the cloud top. |
| 2. Mature: | When the droplets become too large for the updrafts to hold, they fall to the surface, creating a downward motion in the surrounding air. The resulting downdraft may reach a velocity of 2500 f.p.m. The down-rushing air spreads out at the surface. The leading edge of this wind is referred to as a gust front. As the thunderstorm advances, a rolling, turbulent, circular-shaped cloud may form at the lower leading edge of the cloud, called the Roll Cloud. |
| 3. Dissipating: | Eventually the downdrafts begin to spread out within the cell. Because of this, the entire cell begins to weaken. Soon, the upper level winds often blow the top of the cloud downwind, creating the anvil shape. The anvil does not mean the storm is over because severe weather can still occur at this stage. |
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