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| Weather | State of the atmosphere at a specific time and place, determined by factors including air pressure, amount of moisture in the air, temperature, wind, and precipitation |
| Humidity | Amount of water vapor held in the air |
| Relative humidity | Measure of the amount of moisture held in the air compared with the amount it can hold at a given temperature; can range from 0 percent to 100 percent |
| Dew point | Temperature at which air is saturated and condensation forms |
| Fog | A stratus cloud that forms when air is cooled to its dew point near the ground |
| Precipitation | Water falling from clouds - including rain, snow, sleet, and hail - whose form is determined by air temperature |
| Station model | Indicates weather conditions at a specific location, using a combination of symbols on a map |
| Isotherm | Line drawn on a weather map that connects points having equal temperature |
| Isobar | Lines drawn on a weather map that connect points having equal atmospheric pressure; also indicate the location of high and low pressure areas and can show wind speed |
| Barometer | Instrument used to detect the barometric pressure |
| Vortices | masses of whirling gas or liquid |
| Barber Pole | A thunderstorm updraft with a visual appearance including cloud striations that are curved in a manner similar to the stripes of a barber pole. The structure typically is most pronounced on the leading edge of the updraft, while drier air from the rear flank downdraft often erodes the clouds on the trailing side of the updraft. |
| Air mass | a large volume of air with nearly the same temperature and humidity at different locations at the same altitude |
| Front | the boundary between two air masses |
| High Pressure System | a large weather system that surrounds a center of high pressure |
| Low Pressure System | a large weather system that surrounds a center of low pressure |
| Tropical Storm | a low-pressure system that starts near the equator and has winds that blow 65 kilometers per hour |
| Hurricane | a tropical low-pressure system with winds blowing at speeds of 120 kilometers per hour or more |
| Storm Surge | a local exceptional flood of ocean water |
| Blizzard | a blinding snowstorm with winds at least 56 km per hour and low temperatures |
| Thunderstorm | develop when an updraft of warm humid air releases latent heat and become unstable |
| Meteorologist | a scientist who studies weather |
| Air mass thunderstorms | typically do not have very high winds, hail, or much lightning associated with them, usually created by convective uplift of warm, moist, and unstable air, t |
| cumulus stage | initial stage of development, During this stage warm, moist, and unstable air is lifted from the surface,As the air ascends, it cools and upon reaching its dew point temperature begins to condense into a cumulus cloud. Near the end of this stage precipitation forms. |
| mature stage | the second stage of development, moist updrafts continue to feed the thunderstorm while cold downdrafts begin to form. The downdrafts are a product of the entrainment of cool, dry air into the cloud by the falling rain. As rain falls through the air it drags the cool, dry air that surrounds the cloud into it. As dry air comes in contact with cloud and rain droplets they evaporate cooling the cloud. The falling rain drags this cool air to the surface as a cold downdraft. |
| dissipating stage | the final stage of development,when the thunderstorm dissolves away. By this point, the entrainment of cool air into the cloud helps stabilize the air. In the case of the air mass thunderstorm, the surface no longer provides enough convective uplift to continue fueling the storm. As a result, the warm updrafts have ceased and only the cool downdrafts are present. The downdrafts end as the rain ceases and soon the thunderstorm dissipates. |
| Lightning | a massive discharge of electricity in response to a charge differential. |
| thunder | massive discharge rapidly heats the air sending a shockwave through the atmosphere we hear |
| tornado | sometimes called twisters, or cyclones, are violent windstorms that take the form of a rotating column of air, or vortex, that extends downward from a cumulonimbus cloud |
| tornado alley | The region of highest concentration of tornados, a region that stretches from eastern Nebraska through central Kansas and Oklahoma in to the panhandle of Texas. |
| Fujita scale | Developed in 1971 by T. Theodore Fujita of the University of Chicago, measure the severity of a tornado |
| Enhanced F Scale | An update to the the original F-scale by a team of meteorologists and wind engineers, to be implemented in the U.S. on 1 February 2007. |
| entrainment | a process by which falling precipitation within the cloud causes drag on the air and initiates a downdraft that is further aided by the influx of cool, dry air surrounding the cloud |
| gust front | Downdrafts from the thunderstorm cells reach the surface and spread out to produce an advancing wedge of cold air, |
| roll cloud | formed as warm air is lifted along its leading edge of a gust front |
| supercell | a single, very powerful thunderstorm cell that at times may extend to heights of 20 kilometers (65,000 feet) and persist for many hours. |
| mesocyclone | a column of cyclonically rotating air, within which tornadoes often form. |
| Squall lines | relatively narrow, elongated bands of thunderstorms that develop in the warm sector of a middle-latitude cyclone, usually in advance of a cold front. |
| dryline | a narrow zone along which there is an abrupt change in moisture |
| mesoscale convective complex (MCC) | consists of many individual thunderstorms that are organized into a large oval to circular cluster. |
| sheet lightning | most common, occurs within and between clouds. |
| cloud-to-ground lightning | less common but more dangerous type of lightning |
| vortex | rotating column of air |
| suction vortices | Within many stronger tornadoes, called multiple vortex tornadoes, are smaller intense whirls called that rotate within the main vortex. |
| funnel cloud | narrowing column of rotating air stretches downward |
| tornado watch | issued to alert the public to the possibility of tornadoes over a specified area for a particular time interval. |
| tornado warning | issued by local offices of the National Weather Service when a tornado has been sighted in an area or is indicated by weather radar |
| Doppler radar | can identify the initial formation and subsequent development of the mesocyclone within a thunderstorm that frequently precedes tornado development. |
| severe weather | violent disturbance of the atmosphere |
| cyclone | wind system circulating around a low pressure center |
| warm-core cyclones | tropical cyclone |
| wave cyclone | synoptic weather sys formed by the interaction between cold and warm air along the polar front at 30-60 N/S |
| extratropical cyclone | synoptic weather sys formed by the interaction between cold and warm air along the polar front at 30-60 N/S |
| midlatitude cyclone | synoptic weather sys formed by the interaction between cold and warm air along the polar front at 30-60 N/S |
| tropical cyclone | synoptic weather sys formed by the interaction of warm ocean water temperatures and Coriolis effect between 5-30 deg N/S latitude |
| synoptic weather system | spans several hundred to several thousand km |
| storm surge | local exceptional flood of ocean water |
| cell | an updraft of warm humid air |
| supercells | thunderstorms with multiple updrafts |
| funnel cloud | a tornado funnel that does NOT touch the ground |
| arid region | average rainfall less than 250 mm |
| drought | an extreme weather phenomenon in which a region experiences below average precipitation for an extended period |
| semiarid region | average annual rainfall 250 to 500 mm |
| desert | an arid land (less than 250 mm rainfall) |
| most extensive deserts | Sahara, Kalahari, Great Australian, Rub-al-Khali |
| subtropical desert | associated with circumglobal belts of divergence at 20-30 deg N/S, anticyclonic regions of high pressure |
| continental interior desert | formed because wind that travels a very long distance over land, especially land rising to high plateaus, eventually contains so little water vapor none is available for precipitation |
| rainshadow desert | a mountain range creates a barrier to the flow of moist air, causing orographic lifting and heavy rains on the windward side and a zone of low precipitation on the downwind |
| coastal desert | occur along western margins of some continents, the upwelling of cold bottom currents cools maritime moisture off shore, decreasing it's ability to hold moisture. As air meets land it condenses forming fog, but no precipitation. |
| hot desert | rainfall average low, summer temperatures high |
| cold desert | rainfall average low, summer temperatures low |
| desertification | expansion of desert conditions into adjacent areas |
| 1930s Dust Bowl | dust storms swept the Great Plains triggered by a multi-year drought and poor land-use practices. |
| 1970s Sahel Famine | drought stricken region extended from Atlantic to Indian ocean, triggered by mutli-year drought, over rapid increase in human and livestock population resulting in severe overgrazing |
| laminar flow | where air flow is smooth |
| turbulent flow | where air flow is disturbed |
| dust storm | fine sediment carried upward to turbulent air, strong winds can carry very fine dust up into troposphere where it can be transported thousnads of miles by geostrophic winds |
