Download WEATHER FRONTS

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WEATHER FRONTS
Within a natural or designed system, the transfer of energy drives
the motion and/or cycling of matter. Therefore, the movement of
water and energy in the atmosphere can determine weather
patterns. For example, many weather patterns are caused by
differences of temperature in air masses.
Fronts occur at the boundary where warm and cold air masses meet. There are four types of
fronts: cold front, warm front, stationary front, and occluded front. Warm air masses are
forced to rise and expand over and above cold air masses, and cold air masses wedge
underneath warmer air masses. Cool air is more dense and tends to sink. Warm air is less dense
and tends to rise. As the warm air cools, the moisture condenses to form clouds. Rain or snow
may form if the warm air continues to rise and expand.
Cold Front:
A cold front is a situation where a cold air mass is advancing upon a
warm air mass. Cold, dense, high pressure air mass moves quickly towards a warm, less
dense, low pressure air mass. The warm air rises quickly producing fast, violent
thunderstorms followed by clear skies.
Cold fronts produce cumulonimbus clouds (anvil shaped, thunderstorm clouds). Big thunderstorms in
the summer and snowfalls in the winter are the weather conditions associated with cold fronts.
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Warm Front:
A warm front is a
situation where a warm air mass is
advancing upon a cold air mass. Warm,
less dense, low pressure air mass moves
towards a cold, dense, high pressure air
mass. The warm air rises above the cold
air producing cloudy, rainy skies for many
days. Warm fronts often produce
nimbostratus clouds. Nimbostratus clouds
are rain clouds that are in layers. These are clouds that seem to cover the whole sky on
rainy, overcast days. Steady, long-lasting rains in the summer and steady snowfalls in the
winter are weather conditions associated warm fronts.
Stationary Front:
Stationary fronts occur
when neither warm nor cold air
advances. The two air masses reach a stalemate. A
stationary front is a situation where a cold air mass and
warm air mass meet and neither mass is displacing the
other. Warm, less dense, low pressure air mass moves
towards a cold, dense, high pressure air mass. The air
masses stay essentially in one place, or the air masses
stay stationary. Stationary fronts often produce
nimbostratus clouds. Nimbostratus clouds are rain clouds
that are in layers. These are clouds that seem to cover the whole sky on rainy, overcast
days.
Occluded Front: An occluded front occurs when warm, cool, and cold air masses
come together. They are not as common as cold, warm, or stationary fronts. Weather
conditions associated with an occluded front can be divided into three categories: before
passing, while passing, and after passing. Occluded fronts cause storms.
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True or False: For any false statement, change the word(s) in the statement that would
make the statement true.
1. Many weather patterns are caused by differences of temperature in air masses.
2. Fronts occur on opposite sides of air masses.
3. Warm air masses rise and expand over cold air masses.
4. Cold air masses stay below warm air masses because they are less dense.
5. When warm air rises, the water vapor in the air infiltrates.
6. A cold front occurs when a cold air mass runs into a warm air mass.
7. Cold fronts cause violent storms followed by clear skies.
8. Cold fronts cause violent storms because there is a lot of sinking air.
9. Cirrus clouds are often associated with cold fronts.
10. Cumulonimbus clouds are associated with thunderstorms.
11. Nimbostratus clouds are shaped like an anvil.
12. In a warm front, a cold air mass is approaching a warm air mass.
13. A warm front results in warm, less dense air rising.
14. Nimbostratus clouds are associated with warm fronts.
15. Steady, long-lasting rains in the summer and steady snowfalls in the winter are weather
conditions associated with warm fronts.
16. Cumulonimbus clouds cover the whole sky and cause rainy, overcast days.
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17. Stationary fronts occur when neither warm nor cold air advances.
18. In a stationary front, the air masses are moving across far distances.
19. Occluded fronts occur when warm, cool, and cold air masses come together.
20. Occluded fronts are more common than warm and cold fronts.
21. The weather associated with occluded fronts are divided into three categories: before
passing, while passing, and after passing.
22. The weather symbol for a cold front is a blue line with triangles pointing towards the
warm air mass.
23. The weather symbol for a warm front is a red line with triangles pointing towards the
cold air mass.
24. The weather symbol for a stationary front has both half circles and triangles.
25. Fronts occur where warm and cold air masses meet.
26. Saline experiences a violent thunderstorm and thirty minutes later there are clear skies.
This means a warm front has passed through.
27. Cold fronts move faster than warm fronts.
28. Ann Arbor has an entire week of overcast skies and rain. This means a cold front has
passed through.
29. A cold front occurs when a high pressure air mass runs into a low pressure air mass.
30. A warm front occurs when a high pressure air mass runs into a low pressure air mass.
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