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 Nīno~ 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.