Fronts and Severe Weather

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Fronts and Severe Weather

• How do fronts affect the weather?
• When fronts move through an area, the result is
  usually precipitation and a change in wind
  direction and temperature.
• air mass a large body of air where temperature
  and moisture content are similar throughout
• front the boundary between air masses of
  different densities and usually different
  temperatures

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Fronts and Severe Weather, continued

• Interactions between air masses have predictable
  effects on the weather in a given location.
• Clouds, rain, and sometimes snow can occur at
  fronts.
• Front types include
• warm fronts
• cold fronts
• stationary fronts

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Fronts and Severe Weather, continued

• Lightning is a discharge of atmospheric
  electrical energy.
• Water droplets and ice crystals in thunderclouds
  build up electrical charges.
• Lightning is a big spark that jumps between
  clouds or between clouds and Earth to equalize
  the charge.
• Lightning heats the air so fast that the air
  expands faster than the speed of sound.
• The shockwave created is thunder.

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Fronts and Severe Weather, continued

• Tornadoes are funnels of high-speed wind.
• Tornado winds are the most violent winds on
  Earth.
• Wind speeds may reach up to 500 km/h.
• Tornadoes typically form along a front between
  cool, dry air and warm, humid air.
• funnel cloud a column of water droplets
• Tornadoes are fast moving and unpredictable.

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Tornado
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Fronts and Severe Weather, continued

• Hurricanes are large, rotating tropical storm
  systems.
• These storms are called
• hurricanes in North America and the Caribbean
• cyclones in the Indian Ocean
• typhoons in the western Pacific
• tropical depressions intense low-pressure areas
  that can become hurricanes

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Fronts and Severe Weather, continued

• Hurricanes are powered by energy released as
  water vapor condenses to form clouds.
• The center of a hurricane is called the eye.
• The eye is usually calm.
• Hurricane winds can reach speeds greater than 250
  km/h.

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Climate

• How is climate different from weather?
• Weather changes from day to day, but climate does
  not change as quickly.
• climate the average weather conditions in an
  area over a long period of time

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Climate, continued

• Temperatures tend to be higher close to the
  equator.
• Sunlight strikes the earth more directly close to
  the equator.
• The suns rays are less concentrated at the
  poles, and do not warm the atmosphere as much.

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Climate, continued

• Earths tilt and rotation account for our
  seasons.
• When the North Pole is tilted toward the sun, the
  Northern Hemisphere experiences summer.
• There is more daylight, and the temperature
  increases.
• Earth is farthest from the sun on July 4.
• When the South Pole is tilted toward the sun, the
  Southern Hemisphere experiences summer.

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Climate, continued

• Earths surface features affect climate.
• topography the size and shape of the land
  surface features of a region, including its
  relief
• Variations in topography affect the climate of a
  region.
• Mountains can trap moisture on one side.
• Deserts may form on the dry side of a mountain.
• Broad flat surfaces allow winds to merge on the
  plains.
• Thunderstorms and tornados may form.

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Climate, continued

• Global climate changes over long periods of time.
• Many factors produce changes in Earths climate,
  such as
• eruptions of volcanoes
• shift of the continents
• changes in Earths tilt
• Many scientists think that increases in
  human-made greenhouse gases have caused the
  recent increase in global average temperature.