Weather Fronts

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Global Convection Current Noun

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[gloh-buhl kuhn-vek-shuhn kur-uhnt]

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Global Convection Current

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A large-scale movement of air caused by the uneven heating of the Earth's surface, distributing thermal energy around the planet.

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Example: This diagram shows how warm air rises at the equator, cools and sinks at the poles, creating large circular air patterns called global convection currents.

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Air Mass Noun

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[air mas]

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Air Mass

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A large body of air that has similar temperature and moisture characteristics throughout its horizontal extent.

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Example: This map shows large bodies of air, called air masses, which are classified by their temperature (cold/polar, warm/tropical) and moisture (dry/continental, wet/maritime).

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Air Density Noun

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[air den-si-tee]

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Air Density

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The mass of air per unit of volume, which causes colder, denser air to sink and warmer, less dense air to rise.

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Example: Warm air over the land becomes less dense and rises, while cooler, denser air from the sea moves in, creating a sea breeze.

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Front Noun

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[fruhnt]

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Front

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A boundary line where two different air masses meet, typically causing weather changes and the formation of precipitation.

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Example: This diagram shows a cold front, where a dense mass of cold air moves in and forces warmer air to rise rapidly, causing clouds to form.

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Precipitation Noun

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[pri-sip-i-tey-shuhn]

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Precipitation

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Any form of water, such as rain, snow, sleet, or hail, that falls from the atmosphere to the Earth's surface.

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Example: This diagram shows that precipitation falls as snow when the air temperature stays below freezing (0°C) from the clouds all the way to the ground.

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Cold Front Noun

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[kohld fruhnt]

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Cold Front

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A front where a cold air mass moves under and displaces a warm air mass, often producing thunderstorms and heavy rain.

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Example: This diagram shows the weather map symbol for a cold front (a blue line with triangles) separating a colder air mass from a warmer one.

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Warm Front Noun

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[wawrm fruhnt]

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Warm Front

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A front where a warm air mass moves over and gradually replaces a colder air mass, often bringing clouds and prolonged rain.

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Example: This diagram shows how a warm front forms when a moving warm air mass slides up and over a slower, colder air mass, causing clouds and precipitation.

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Occluded Front Noun

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[uh-klood-ed fruhnt]

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Occluded Front

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A front that forms when a warm air mass is caught and lifted between two colder air masses, bringing significant precipitation.

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Example: This weather map shows an occluded front (alternating triangles and semicircles) forming as a faster cold front overtakes a slower warm front.

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Stationary Front Noun

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[stey-shuh-ner-ee fruhnt]

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Stationary Front

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A front where a cold and a warm air mass meet but neither has the force to move the other.

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Example: This diagram shows a stationary front, where a cold air mass (blue) and a warm air mass (red) meet but neither is strong enough to move the other.

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Low Pressure Noun

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[loh presh-er]

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Low Pressure

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An atmospheric condition where air is rising, often associated with cloudy, rainy, or stormy weather due to air cooling.

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Example: At higher altitudes, there is less air in the column above, creating an area of lower atmospheric pressure compared to the higher pressure at lower altitudes.