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Unformatted text preview: Questions for Review 1. What is a thunderstorm? A. A convective storm (cumulonimbus cloud) with lightning and thunder. Thunderstorms can be composed of an ordinary cell, mulitcells, or a rapidly rotating supercell. 2. What atmospheric conditions are necessary for the development of an ordinary cell (air mass) thunderstorm? A. Ordinary (air-mass) thunderstorms generally form in warm, humid weather, are usually short-lived and rarely produce strong winds and large hail. 3. Describe the stages of an ordinary cell (air mass) thunderstorm). A. There are three stages describing the life cycle of an air-mass thunderstorm * Total life span for an air mass thunderstorm is about 45-60 minutes cumulus stage- Observed as a growing cumulus cloud Dominated by updraft transporting warm, moist air upward No precip is reaching the surface at this stage, though it begins to form in the cloud Air parcel temperatures in the cloud are warmer than the surrounding air. The mixing of environmental air and air in the cloud is called entrainmen t mature stage- Storm is most intense Cloud tops can reach tropopause height generating overshooting tops, can be seen in satellite imagery Ice and water may both be present in the cloud Lightning and thunder may be present Storm is characterized by warm updraft and cold, downdraft Precip is reaching the surface Downdraft can produce strong, gusty winds at surface Dissipating stage- st orm is dominated by the downdraft Precipitation intensity at the ground weakens end up with a cold pool air at the ground, warm air is now aloft hence, the storm has stabilized the environment 4. How do downdrafts form in thunderstorms? A. A downdraft is the sudden descent of cool or cold air to the ground. Unstable a ir that is forced upward will continue to rise, and air that is forced downward will continue to sink. As it rises it cools and some of the water vapor will condense, forming the familiar tall cumulonimbus cloud that is the thunderstorm. The mechanisms that can initiate the movement of air are: Differential heating uneven heating of the ground and lower atmosphere (i.e. pavement is hotter than the grass). F ronts- are the boundary between two air masses of different temperatures. D rylines- are the boundary between two air masses of different moisture content and separate warm moist air from hot dry air. Outflow boundaries- are a result of the rush of cold air as a thunderstorm moves overhead. Terrain- As air encounters a mountain it is forced up the slope of the terrain. 5. Why do ordinary cell thunderstorms most frequently form in the afternoon? A. The most common thunderstorms are air mass thunderstorms that occur in the mid- latitudes in summer and at the equator all year long. Air mass thunderstorms normally develop in late afternoon hours when surface heating produces the maximum number of convection currents in the atmosphere....
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- Spring '10