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A transition zone between two air masses of
different densities is called a front. |
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There is usually a temperature difference across
a front as well. |
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The humidities may differ as well. |
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Do not move. |
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On the map, semicircles point to warmer air and
triangles point to cooler air. |
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Here, air blows parallel to the fronts. |
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Cold air is replacing warm air. |
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The triangles indicate the direction the front
is moving. |
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Sharp temperature changes over short distance |
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Changes in the air’s moisture content (dew pt.) |
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Shifts in wind direction |
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Pressure and pressure changes |
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Clouds and precipitation patterns |
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Cold dense air forces warm air upwards. |
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Warm moist air rises and condenses into clouds,
producing rain showers at the front. |
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Leading edge of front is steep (1:50 for a 25
knot front). |
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Frontolysis – temperature contrast lessens and
front weakens |
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Frontogenisis – temperature contrast increases
and front strengthens |
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Warm air is replaces cold air. |
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The semicircles indicate the direction the front
is moving. |
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Front moves slowly (10 knots), about half the
speed of an average cold front. |
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Warm air rises over cold air, |
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creating clouds and rain showers ahead of the front. |
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Leading edge of front has a gentle slope
(1:300). |
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There is a temperature inversion (frontal
inversion) just ahead of the front. |
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When a cold front catches up to and overtakes a
warm front, the boundary is called a occluded front (or occlusion). |
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On a weather map, there are alternating
cold-front triangles and warm-front semicircles pointing in the same
direction. |
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The cold air of the cold-front lifts both the
warm and cold air ahead of it. |
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The cold air of the cold front rises over the
colder air ahead of it. |
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When two air masses meet, a front is created. |
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There are four kinds of fronts: |
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Stationary – not moving |
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Cold – cold air replaces warm air |
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Warm – warm air replaces cold air |
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Occluded – cold front catches up with warm front |
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