Weather A - Z (A-C)

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Weather A - Z (A-C)

Post by ICE » Fri Apr 28, 2006 9:56 am

Advisory - A forecast issued by the National Weather Service to highlight conditions that require caution, but are not thought to be immediately life threatening.

Air - The mixture of gases, which form the atmosphere of the Earth.

Air Pollution – Chemicals or substances in the atmosphere that are directly or indirectly harmful to living things.

Air Pressure - The weight of air pressing down on earth. Air pressure can change from place to place, and this causes air to move, flowing from areas of high pressure toward areas of low pressure. It’s the same as barometric pressure.

Alberta Clipper - A fast-moving low pressure system that occurs during the winter and sweeps southeast from Alberta, Canada, across the northern Great Plains and Midwest of the United States. These storms usually bring a few inches of snow.

Almanac - A calendar that uses astronomical information and weather data. Almanacs list tide data, give the positions of the stars and forecast weather each day.

Anemometer - A weather instrument that measures the wind speed.

Anticyclone - A high-pressure system that moves in a clockwise motion. These bring you sunny skies.

Arctic Air - An air mass that originates over Canada and brings us cold temperatures.

Atmosphere - A layer of gases surrounding a planet. The Earth’s atmosphere is divided into five layers: exosphere, thermosphere, mesosphere, stratosphere, and troposphere.

Aurora Borealis - It’s often called the "northern lights". It occurs 50 to 100 miles above the earth, when energetic particles from a solar storm cause the gases in the upper atmosphere to glow. Auroras can last between a few minutes to several hours. It’s common across Alaska and northern Canada.

Autumn - The season of the year that occurs after summer and before winter. Autumn officially begins in late September.

Avalanche - A large body of snow, ice or rock and debris sliding down a mountain. Worldwide, about one million snow avalanches occur per year.

Backing Wind - A wind that changes its direction in a counter clockwise motion. For example, a northwest wind changing to a west wind.

Barometer - An instrument that measures air pressure.

Barometric Pressure - It’s the same as air pressure. The pressure exerted by the atmosphere at a given point.

Bermuda High - It’s a weather system that often dominates the eastern United States during the summer. A semi-permanent subtropical high-pressure system over the North Atlantic Ocean brings in warm and humid air for many days or weeks at a time. It gets its name because it is sometimes centered near Bermuda. It contributes to U.S. heatwaves when it extends west into the Gulf of Mexico and across the Deep South.

Blizzard - An intense winter storm with winds of 35 m.p.h. or higher with falling and/or blowing snow to reduce visibility below 1/4 mile for at least three hours.

Blowing Snow Advisory - When wind driven snow reduces the surface visibility causing dangerous driving conditions. Blowing snow can be falling or snow that has already accumulated on the ground but is picked up and blown by strong winds.

Breeze - A light wind.

Ceiling - The height of the lowest layer of broken or overcast cloud layer.

Cirrus Clouds - Thin, wispy clouds that form high in the atmosphere as their water vapor freezes into ice crystals. Cirrus clouds are a principle cloud type.

Clear Sky - When the sky has no clouds.

Climate - It describes the average weather conditions in a certain place or during a certain season. Weather may change from day to day, but climate changes only over hundreds or thousands of years. Many animals and plants need one kind of climate to survive. Dolphins and palm trees can live only in a warm climate, while polar bears and spruce trees need a cold climate.

Clouds - A visible collection of tiny water droplets or, at colder temperatures, ice crystals floating in the air above the surface. Clouds come in many different sizes and shapes. Clouds can form at ground level, which is fog, at great heights in the atmosphere, and everywhere in between. Clouds offer important clues to understanding and forecasting the weather.

Coastal Flooding - It’s when winds and/or tides cause a rise in the sea level that floods coastal areas.

Cold Front - A boundary between two air masses, one cold and the other warm, moving so that the colder air replaces the warmer air.

Condensation - The change of water vapor to liquid water, as when fog or dew forms.

Contrails - Long, narrow, ice-crystal clouds that form behind jet planes flying at high altitudes in below-freezing temperatures. They result from the condensation of water vapor remaining in jet exhaust.

Coriolis Force - A force that deflects moving objects to one side because of the Earth’s rotation. The object is still going straight but the Earth moves underneath it, making it look like it is moving to one side. In the Northern Hemisphere, the Coriolis Force deflects objects to the right.

Cumulonimbus - A dense and vertically developed cloud that produces thunderstorms. The cloud can bring heavy showers, hail, lightning, high winds and sometimes tornadoes.

Cumulus Clouds - Fluffy, mid-level clouds that develop in towering shapes and signal fair weather. Cumulus clouds are a principle cloud type.

Cyclone - A low pressure system. It is a term variously applied to tornadoes, waterspouts, dust storms, hurricanes and even to any strong wind.

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