Weather PatternsThere are warm and cool air masses in Earth. Air mass is a large body of air that has fairly uniform physical properties, such as temperature and moisture content, at any other given altitude. The two different air masses are produced because of the uneven heating of the Earth (warmer in the equator, cooler in the pole). Warm air masses are produced near the equator, and the cool air masses are produced near the pole. These air masses don’t stay where they are, but circulate around the Earth. When two air masses meet each other, it creates a boundary between the air masses and it is called a front. Clouds and precipitation take place in the front. There are four types of front, and they are cold fronts, warm fronts, stationary fronts, and occluded fronts. The are also other weather patterns and these terms will be explained below.
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Cold Fronts• Occurs when a cold air mass overtakes a warm air mass
• Warm air is lifted rapidly • Cold air is denser and stay near the ground • Cumulus and cumulonimbus clouds form • Strong winds, severe thunderstorms, and large amount of precipitation • Steep and travel quickly, the weather lasts for only short time, temperature drops |
Warm Fronts• Occurs when a warm air mass overtakes a cold air mass
• Less steep than the cold front • Gentle slope because the advancing war air mass gradually moves up and over the cold air mass • Status clouds form • Steady rain, occasionally heavy rain or thunderstorm • Falt layers of clouds that cover much • Falt layers of clouds that cover much |
Stationary Fronts• Neither air masses are moving
• Often results in clouds and steady rain or snow for several days |
Occluded Fronts• When warm air mass is caught between two air masses
• Warm air rises, and cools, its water vapor typically condenses • Cloudy skies and precipitation |
Other Weather Patterns
Cyclones• Weather system with a center of low air pressure
• Air spirals in toward the center of a cyclone (high to low) • Associated with clouds, precipitation, and stormy weather |
Anticyclones• Weather system with a swirling center of high air pressure
• Clockwise in the Northern Hemisphere (Coriolis effect) • Air flows away from that center • Clear skies, very little precipitation, and generally calm conditions |
Thunderstorms• Small weather system that includes thunder and lightning
• Strong winds and heavy rain or hail • Form when columns of air rise within a cumulonimbus cloud • Cold front forms |
Lightning• Sudden electrical discharge in the atmosphere
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Thunder• The sound produced by rapidly expanding air along the path of a lightning discharge
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Tornado (Twister)• A small but intense windstorm that takes the form of a rotating column of air that touches the ground
• Forms when a vertical cylinder of rotating air develops in a thunderstorm |
Thunderstorms• A large tropical cyclone with winds of at least 119km per hour
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