Tornado Glossary

air pressure Air pressure is the weight of the column of air that extends from the ground (or water's surface) to the top of the atmosphere. Air pressure is also called barometric pressure; it is measured by a barometer. The air pressure is very low in a tornado.	anemometer An anemometer is a weather instrument that measures wind speed. Anemometers are destroyed in severe tornadoes.	barometer A barometer is a device that measures air (barometric) pressure. It measures the weight per square inch of the column of air that extends from the instrument to the top of the atmosphere.	barometric pressure Barometric pressure is the weight of the column of air that extends from the ground (or water's surface) to the top of the atmosphere. It is also called air pressure. Air pressure is measured by a barometer. 29.92 is the average air pressure at sea level. Falling barometeric pressure usually means that a storm is coming. Barometric pressure falls before a tornado.
clockwise Clockwise motion goes in a circle in the same direction as a clock. In the Southern Hemisphere (south of the equator), most tornadoes rotate in a clockwise direction.	counterclockwise Counterclockwise motion goes in a circle in the opposite direction from the way a clock moves. In the Northen Hemisphere (north of the equator), most tornadoes rotate in a counterclockwise direction.	cumuliform cloud A cumuliform cloud is a type of cloud that takes the form of mounds or towers. This type of cloud is associated with thermal convection (movement caused by heat).	cyclone A cyclone is a general term for a closed, rotating wind around an area of low atmospheric pressure. Most cyclones rotate in a counterclockwise direction in the Northern Hemisphere (north of the equator) and in a clockwise direction in the Southern Hemisphere (south of the equator).
degree A degree is a unit of measurement of an angle; a degree is also written °. There are 360 degrees in a circle. Each degree is divided into 60 minutes, written as the symbol '. For example, 10 and a half degrees is written 10° 30'. Latitude and longitude are in measured in degrees.	EF-Scale The EF-scale (enhanced F-scale) classifies tornado wind speeds into five categories The Enhanced F Scale, the EF scale (replacing the older F scale) is now used to rate tornadoes. The original scale was named for Dr. Theodore Fujita, who developed the original F-scale in 1971. Wind speeds are at least 3-second gusts. EF-0 -- Winds 65-85 EF-1 -- Winds 86-110 mph EF-2 -- Winds 111-135 mph EF-3 -- Winds 136-165 mph EF-4 -- Winds 166-200 mph EF-5 -- Winds over 200 mph.	equator The equator is an imaginary circle around the Earth, halfway between the North and South Poles.	eye The eye is the calm, roughly circular center of a cyclonic storm. In the eye, it is relatively calm (there is little wind). The eye of a tornado may be only a few feet or yards across.
F-Scale The F-scale rates wind estimates (not measurements) based on subsequent damage. Tornadoes are classified according to the F-scale; an F-5 tornado is the most dangerous type. F-0 40-72 mph, chimney damage, tree branches broken F-1 73-112 mph, mobile homes pushed off foundation or overturned F-2 113-157 mph, considerable damage, mobile homes destroyed, trees uprooted F-3 158-205 mph, roofs and walls torn down, train cars overturned, cars thrown F-4 207-260 mph, well-made walls destroyed F-5 261-318 mph, homes lifted off foundation and carried considerable distances, cars thrown as much as 100 meters.	forecast A forecast is a prediction of future weather made by meteorologists.	Fujita, Theodore Dr. Tetsuya Theodore (Ted) Fujita (Oct. 23, 1920 - Nov. 19, 1998) was a pioneering meteorologist who revolutionized the study of severe storms. Dr. Fujita was the first person to realize that there are multiple vortex tornadoes (1965), downbursts and microbursts. He also developed a scale for measuring wind speed in 1971; it links damage to wind speed. This scale is called the Fujita-scale or the F-scale.	funnel cloud A funnel cloud is a rotating column of wind that does not touch the ground. A funnel could may turn into a tornado (a tornado touched the ground).
gustnado A gustnado is a weak eddy or whirlwind. Although it can do minor damage, a gustnado is not a tornado.	hail Hail is frozen precipitation (ice). Large hail can cause damage. Hail is formed in most mid-latitude thunderstorms, but most hail melts before it reaches the ground. Severe hail is defined as being 3/4 inch or more across, bigger than a dime.	isobar An isobar is a line on a weather map that represents constant barometric (air) pressure.	jet stream The jet stream is a narrow, powerful wind that flows high the atmosphere (in the upper troposphere).
landspout A landspout is a term for a small, weak tornado that looks like a waterspout.	latitude Latitude is the angular distance north or south from the equator to a particular location. The Equator has a latitude of zero degrees. The North Pole has a latitude of 90 degrees North; the South Pole has a latitude of 90 degrees South.	longitude Longitude is the angular distance east or west from the north-south line that passes through Greenwich, England, to a particular location. Greenwich, England, has a longitude of zero degrees. The farther east or west of Greenwich you are, the greater your longitude. The Midway Islands (in the Pacific Ocean) have a longitude of 180 degrees (they are on the opposite side of the globe from Greenwich).	meteorology Meteorology is the science that deals with weather. A scientist who studies weather is called a meteorologist.
multiple-vortex tornado A multiple-vortex tornado (also called a multivortex tornado) is a tornado that has two or more small subvortices that orbit (circle) the center of a larger tornado.	NOAA The National Oceanic and Atmospheric Administration is a US government organization that tracks and studies storms, and issues advisories about the storms.	Northern Hemisphere The Northern Hemisphere is the half of the Earth that is north of the equator.	nowcast A nowcast is a prediction of the weather likely in the immediate future (the next few hours) made by meteorologists.
overcast When the sky is overcast, clouds cover the sky.	precipitation Precipitation is water in all forms that falls from clouds to the earth's surface, including rain, snow, sleet, and hail.	Prime Meridian The prime meridian (0 degrees longitude) is the meridian (a circular arc or great circle of longitude that meets at the North and South Poles and connects all places of the same longitude) that passes through Greenwich, England.	RADAR RADAR is a device that detects objects at a distance (like hurricanes) using radio waves. RADAR stands for "RAdio Detecting And Ranging."
rope tornado The rope tornado is one that is rope-shaped -- long, snake-like, and narrow. The rope stage of a tornado is often the last stage in its existence.	significant tornado A significant tornado is one that does F2 or greater damage on the Enhanced F scale.	Southern Hemisphere The Southern Hemisphere is the half of the Earth that is south of the equator.	supercell A supercell is a dangerous type of thunderstorm that has a rotating updraft (called a mesocyclone). This type of storm can last for hours and may produce large hail, strong winds, lightning, flash floods, and tornadoes.
thunderstorm A thunderstorm (also called an electrical storm) is a storm that has lightning and thunder; they ofter have strong winds, rain, and/or hail. Thunderstorms are produced by cumulonimbus clouds.	tornado A tornado is a column-like vortex of rapidly-rotating air in contact with the ground. Winds in the most extreme tornadoes can be over 300 mph (500 km/h). Most tornadoes are short-lived.	Tornado Alley Tornado Alley is an area in mid-USA that has a very high number of significant tornadoes. Tornado Alley extends from central Texas northward to Illinois and Indiana. Tornado Alley extends from central Texas northward to Illinois and Indiana. The heart of Tornado Alley includes parts of Texas, Oklahoma, Kansas, Nebraska, eastern Colorado, and South Dakota.	Tornado classification Tornadoes are classified into five categories, categorized by wind estimates (not measurements) based on damage. The Enhanced F Scale, the EF scale (replacing the older F scale) is now used to rate tornadoes. The scale is named for Dr. Theodore Fujita, who developed the original F-scale in 1971. Wind speeds are at least 3-second gusts. EF-0 -- Winds 65-85 EF-1 -- Winds 86-110 mph EF-2 -- Winds 111-135 mph EF-3 -- Winds 136-165 mph EF-4 -- Winds 166-200 mph EF-5 -- Winds over 200 mph.
tornado warning A tornado warning means that a tornado is expected in the warning area soon. A tornado warning means that lives are in danger in that area, and that people should take cover! The first tornado warning was issued by meteorologists at Tinker Air Force Base, Oklahoma, in 1947.	tornado watch A tornado watch means that a tornado may form in the area, because conditions are favorable for their formation.	tropical cyclone A tropical cyclone is a violent low-pressure weather system in which the central core is warmer than the surrounding winds. If it forms in the Atlantic or eastern Pacific Ocean, it is called a hurricane. If it forms in the western Pacific Ocean, it is called a typhoon.	troposphere The troposphere is the lowest region in the Earth's (or any planet's) atmosphere. On the Earth, it goes from ground (or water) level up to about 11 miles (17 kilometers) high. The weather and clouds occur in the troposphere. In the troposphere, the temperature generally decreases as altitude increases.
turtle A turtle is a device that scientists use to study tornadoes. Turtles look a bit like the animal they are named for; they are short, heavy, armored devices that can withstand a tornado. Turtles measure temperature, pressure and humidity at ground level (they do not measure wind speed).	twister Twister is another name for a tornado.	typhoon A typhoon is a tropical cyclone that forms in the Western Pacific Ocean (west of the International Date Line).	updraft An updraft is a current of air that is flowing upwards.
vortex A vortex is a spinning flow of air.	waterspout A waterspout is a tornado that passes over water. It is a funnel-shaped formation of wind, water and ocean spray.	weather map A weather map is a map that shows weather conditions for a given time. Weather maps show storms, fronts, temperatures, rain, snow, sleet, fog, etc.	weather satellite A weather satellite is an orbiting machine that takes pictures of the Earth's surface that are used for noting the Earth's weather.
wegde Wedge is an informal term for a tornado that is about as wide as is it is tall.

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