Accretion: Clumping together of particles or droplets.
Adiabatic process: A change in temperature without heat being added or taken away... but by pressure changes as air rises or sinks.
Advection: Horizontal movement of meteorological properties, such as heat or humidity.
Advection fog: Fog formed by warm, humid air moving over cooler ground or water.
Air mass: A large body of air with about the same characteristics, such as temperature, pressure, and humidity.
Altimeter: A special barometer used to measure altitude.
Atmosphere: The air that surrounds the Earth.
Barometer: A device used to measure air pressure.
Beaufort Scale: A scale used to classify wind speeds, devised in 1805 by Admiral Francis Beaufort of the British Navy.
Blizzard: Snow falling with winds in excess of 35 mph and visibility of 1/4 mile or less.
Climate: Average weather over a long time period, usually 30 years.
Cold front: An advancing mass of cold air, frequently bringing thunderstorms.
Condensation: The change of water vapor from a gas to a liquid.
Conduction: The transfer of heat within a substance, or between substances through molecular action.
Coriolis Effect: The curving motion of anything, including wind, caused by the Earth's rotation.
Cyclone: An area of low atmospheric pressure with counterclockwise wind motions in the Northern Hemisphere, and clockwise spin in the Southern Hemisphere.
Dew: Water droplets formed by condensation of vapor.
Dew point: A measure of humidity given in terms of the temperature at which dew will start to form.
Drizzle: Falling water drops with a diameter less than 0.02 inch.
Drought: Abnormal lack of precipitation for a given region.
El Nîno: A combination of atmospheric and oceanic events characterized by a warming of the water in the equatorial Pacific ocean.
Flash Flood: Flooding with rapid water rise.
Fog: A cloud on the ground.
Freezing: Changing from a liquid to a solid.
Freezing rain: Supercooled raindrops that freeze when they come into contact with something.
Front: The boundary between air masses of different densities.
Fujita Scale: Wind damage scale devised by Theodore Fujita.
Funnel cloud: A rotating column of air extending from a cloud but not reaching the ground.
Ground fog: A layer of fog, frequently less than 200 feet high, that forms when the ground cools.
Hail: Balls of ice that grow in thunderstorm updrafts.
Halo: A ring or arc forming around the sun or moon caused by ice crystal clouds.
High: A region of high-atmospheric pressure, with clockwise winds in the Northern Hemisphere.
Hurricane: A tropical cyclone with winds over 74 mph.
Inversion: A stable air condition in which air near the ground is cooler than air at elevation.
Jet stream: A narrow band of atmospheric winds with speeds in excess of 57 mph.
Latent heat: Energy stored when water evaporates or ice melts.
Lightning: A visible discharge of electricity associated with thunderstorms.
Low: An area of low atmospheric pressure and counter-clockwise winds in the Northern Hemisphere.
Millibar: A metric unit of air pressure.
Monsoon: Persistent, widespread, seasonal winds that usually bring rain.
National Oceanic and Atmospheric Administration: The U.S. federal agency responsible for describing and predicting changes in the Earth's environment.
National Weather Service: The U.S. federal agency that is responsible for observing and forecasting weather.
Occluded front: A boundary between cool, cold, and warm air masses.
Precipitation fog: Fog that forms when precipitation falls into cold air.
Rain: Falling water drops with a diameter greater than 0.02 inch.
Rainbow: An arc or circle or colored light caused by refraction and reflection of sunlight by water droplets.
Relative humidity: The ratio of the amount of water vapor actually present in air compared to the amount of vapor that the air could maximally hold at a given temperature and pressure.
Saturation: Point at which the amount of water vapor in the air is at a maximum for a given pressure and temperature.
Severe thunderstorm: A thunderstorm with winds exceeding 57 mph, or with hailstones of 3/4 inch or larger.
Shower: Intermittent precipitation of short duration.
Sleet: Frozen raindrops
Snow: Precipitation composed of ice crystals.
Squall line: A line of thunderstorms.
Stable air: Air in which there are few updrafts or downdrafts. Clouds are low and flat.
Stationary front: A warm/cold front boundary with neither cold nor warm air advancing.
Sublimation: Phase change of water directly from vapor to ice, or the reverse.
Thunder: Sound produced by a lightning discharge.
Thunderstorm: Localized storm producing lightning and thunder, often associated with a passing cold front.
Tornado: A strong, rotating column of air that reaches the ground.
Trough: An elongated area of low pressure, running generally north-south.
Typhoon: A tropical cyclone with winds greater than 74 mph in the north Pacific.
Unstable air: Air in which temperature and humidity are favorable for the creation of updrafts and downdrafts.
Upslope fog: Fog that forms in humid air flowing uphill.
Virga: Rain that turns back into water vapor before reaching the ground.
Warm front: A warm/cold air boundary with the warm air advancing.
Water vapor: The gaseous form of water.
Waterspout: A tornado from the bottom of a cloud to the surface of a body of water.
Wind chill factor: Effect of wind blowing away the warmed air near the body.
Return to Clouds home page