20-2 Flashcards
what are fronts and how are they classified?
boundary between where two air masses meet.
Classified according to the temperature of the advancing front, air at the surface goes from high pressure to low so winds occur
how do cold and warm air masses interact?
Cold air masses are more dense, while warm air masses are less dense. When they collide, the cold air lifts the warm air at an angle. Sometimes, air masses move in the same direction at the same speed.
How does a warm front form and move?
when a warm air mass meets a cold air mass. warm air slides up and over the cold air. It moves at half the speed of a cold front and can bring light rain for days.
What type of clouds and weather are associated with a warm front?
As warm air rises, it cools, reaches the dew point, and condenses to form clouds. High cirrus clouds appear first, followed by cirrostratus, altostratus, and eventually nimbostratus, which may produce rain or snow.
How is a warm front represented on a weather map?
shown as a red line with semicircles pointing in the direction it is moving. In the Northern Hemisphere, wind shifts from east to southwest as the front passes, bringing warm, humid conditions.
How does a cold front form and move?
forms when a cold air mass invades a warm air mass, forcing the warm air up rapidly along a steep front. It moves twice as fast as a warm front and is twice as steep.
What type of clouds and weather are associated with a cold front?
As warm air rises, it cools and condenses, forming cumulus and cumulonimbus clouds. This leads to rain and thunderstorms in a narrow band along the front. After it passes, cooler, drier conditions and clear skies follow.
How is a cold front represented on a weather map?
shown as a blue line with triangles pointing in the direction it is moving, toward the warm air mass.
How does a stationary front form?
forms when a warm or cold front collides with another cold front, and neither advances. It can remain in place for several days.
What kind of weather does a stationary front bring?
it produce light winds and light to moderate precipitation across the entire frontal region.
How does an occluded front form?
forms when a cold front with cold air and a warm front with cool air goes in the same direction and merges, and one cold front overtakes the other, forcing the warm air between them to rise.
What kind of weather does an occluded front bring?
they bring strong winds and heavy precipitation at first, followed by light precipitation for several days as they move slowly.
How is an occluded front represented on a weather map?
An occluded front is shown as a purple line with semicircles and triangles pointing in the direction it is moving.
Why is precipitation associated with each type of front?
Warm, moist air is pushed up and cooled, reducing its ability to hold water. As the air becomes saturated, water condenses, leading to precipitation.
What are cyclones and how do they affect weather?
Cyclones are low-pressure systems where warm, less dense air rises, cools, and releases water vapor, leading to thunderstorms, cloudy weather, and rain. They are the main weather producers in the U.S., moving west to east.
How does air move in a cyclone? How is it marked?
in the Northern Hemisphere, air swirls inward counterclockwise due to the Coriolis effect. Cyclones are marked by an “L” at the center.
how do cyclones form?
fronts occur along relatively straight line, but mountains/jet streams can interfere causing air to swirl which can cause a middle-latitude cyclone
what’s the first stage of cyclone formation?
development of stationary front, when two air masses with different temperature move in opposite direction
what’s the second stage of cyclone formation?
Over time front takes on wave shape, hundreds of km long
what’s the third stage of cyclone formation?
Changes in air flow and pressure result in a counterclockwise flow of air
what is occlusion?
cold front moves faster than warm front
what’s the fourth stage of cyclone formation?
Cold front closes in and eventually lifts the warm front, results in occlusion (separated from ground)
what’s the fifth stage of cyclone formation?
Storm is rather strong, heavy rains, pressure in the storm’s center falls, winds speed increase
what’s the sixth stage of cyclone formation?
Within a day or two, the warm air is gone, leaving only cold air. The cyclone loses energy, the surface cools, friction slows the wind, and the counterclockwise flow weakens.
what is airflow aloft?
recycling of the air; air flows from low pressure (rises up) to high pressure (sinks)
How do cyclones exist for a longer time?
surface air moving inward must be balanced by airflow above. Air rises, cools to the dew point, forms rain, then spreads outward at higher levels.
What is an anticyclone and how does it work?
An anticyclone pulls air inward above, then high-pressure air sinks, warms, and holds more moisture, lowering humidity and bringing sunshine. Air flows outward at the surface.
How are cyclones and anticyclones related?
Cyclones and anticyclones are connected because air spreading from an anticyclone feeds into a nearby cyclone.
