NSACAS™ approved document 3-04'/app Official Storm Chaser and Storm Spotter Glossary of Terms and Slang This glossary, authored by Warren Faidley, is the most extensive storm chasing glossary ever assembled. It contains the basic explanations of common technical and slang terms commonly used by storm spotters, meteorologists, storm chasers, scientists and storm chasing media personnel. Many of the definitions have been simplified. Editors note: When quoting directly from this glossary, please credit as follows: ©Warren Faidley/Stormchaser.com Warning! This glossary is provided as a courtesy for educational, safety and reference use only. The text is protected by a ©US Copyright. Single terms may be quoted as references for editorial and educational use. Do not copy, print-out or reproduce the overall text without expressed written permission and licensing from Warren Faidley. Internet users may link to this glossary, but it cannot be copied and placed on webpages. Printed copies of this glossary will be available soon. All proceeds from the sale of this glossary are donated to the Storm Angel™ Foundation: to educate, and assist children who are victims of severe weather. Unauthorized uses or reproductions will be pursued. We thank you for your assistance and honesty. As it is with all types of scientific terminology, such terms are constantly being redefined, and a few are, by nature, controversial. We kindly request that any corrections or suggestions be forwarded to our editor, Mary Baker. Thank you. Words in italics are terms defined elsewhere. Note.... glossary is currently being updated and revised... only first page is available now. Complete glossary will be up by March 15, 2005. D through G     H through M     N through R     S through Z A through C A-bomb: [slang] A thunderstorm or cumulonimbus tower which has a mushroom cloud appearance, similar to an atomic bomb cloud. ©Warren Faidley - do not copy or print without permission AC: Anticipated Convective outlook. Same as convective outlook. ©Warren Faidley - do not copy or print without permission accessory cloud: A cloud that depends on a larger cloud system, such as a thunderstorm, for its development and existence. Roll clouds and shelf clouds are two examples. ©Warren Faidley - do not copy or print without permission advection: The horizontal transfer of an atmospheric property, such as temperature or water vapor. ©Warren Faidley - do not copy or print without permission advisory: A statement issued by the National Weather Service for conditions not warranting a warning. ©Warren Faidley - do not copy or print without permission agitated region/area: [slang] An area where groups of towering cumulus grow and collapse. Such areas sometimes favor eventual severe storm development. ©Warren Faidley - do not copy or print without permission air mass: A large body of air (generally covering thousands of square miles) which has relatively uniform characteristics of humidity and temperature. The boundaries between air masses are called fronts. ©Warren Faidley - do not copy or print without permission air mass thunderstorm: Generally, any thunderstorm not associated with strong dynamics and/or favorable wind shear. ©Warren Faidley - do not copy or print without permission air parcel: An imaginary body of air, a few feet wide, used to visualize the behavior of air. The concept of parcels is often used to estimate atmospheric soundings. ©Warren Faidley - do not copy or print without permission air pressure: The amount of force exerted over an area by air molecules. This force, or weight, is called air pressure. The amount of pressure is often measured by a barometer in units of inches of mercury, or in millibars. The average sea level pressure is 29.92 inches, while a hurricane may have a pressure of 26.55 inches or lower. Rapidly falling air pressures often indicate a disturbance is approaching. ©Warren Faidley - do not copy or print without permission all hazards alert radio or receiver: A radio capable of receiving Emergency Alert System (EAS) broadcasts, including weather watches and warnings. ©Warren Faidley - do not copy or print without permission altimeter: A barometer calibrated to indicate altitude instead of air pressure. Altimeters are commonly used in aircraft. ©Warren Faidley - do not copy or print without permission altocumulus (Ac): White or gray clouds, appearing as rounded masses or rolls, occurring in layers or patches, generally located between 6,500 to 15,000 feet. Altocumulus clouds can indicate a destabilizing atmosphere. ©Warren Faidley - do not copy or print without permission altocumulus castellanus (ACCAS) (pronounced ACK-kas): Clouds generally located between 6,500 to 15,000 feet. The upper portions of these clouds consist of white cumulus clouds, and are taller than they are wide, which gives a turret-shaped appearance. The bases are flat. These clouds may indicate instability aloft and the possibility of storm development. ©Warren Faidley - do not copy or print without permission altostratus (As): Grayish clouds generally located between 6,500 to 15,000 feet, in the form of fibrous, striated or uniform sheets or layers. A widespread, thick layer of altostratus may inhibit surface heating, which can delay or suppress storm development. ©Warren Faidley - do not copy or print without permission anemometer: An instrument, usually consisting of a staff and three cups that rotate with the wind, that measures wind speed. ©Warren Faidley - do not copy or print without permission anticipated convective outlook: A public forecast issued by the SPC several times daily, outlining the area(s) of expected thunderstorms, and the severity of possible storms over the U.S. The potential for severe weather is listed as: approaching severe, slight risk, moderate risk or high risk. The convective outlook is a popular forecast text amongst storm chasers. Also called AC and convective outlook. ©Warren Faidley - do not copy or print without permission anticyclonic rotation: Clockwise rotation (in the Northern Hemisphere as would be seen from above). The opposite of cyclonic rotation. ©Warren Faidley - do not copy or print without permission anticyclonic tornado: A tornadic vortex that turns in a clockwise direction (as opposed to tornadoes that turn in a cyclonic or counterclockwise direction). Less than 1% of all Northern Hemisphere tornadoes are anticyclonic. ©Warren Faidley - do not copy or print without permission anvil cloud: The upper portion of a thunderstorm, often shaped like a blacksmith's anvil, consisting mainly of ice crystals. Anvils may spread out for hundreds of miles from the main storm as jet stream winds carry the clouds downwind. A solid, intact anvil cloud, with backshearing, is usually indicative of a strong storm. The over-shooting tops or domes of anvils may reach above 60,000 feet. ©Warren Faidley - do not copy or print without permission anvil crawlers: [slang-Rhoden] Lightning bolts which spread out underneath a storm's anvil. ©Warren Faidley - do not copy or print without permission anvil rings: [slang] Circular rings or cloud striations sometimes associated with an anvil cloud. Also called "Saturn rings." ©Warren Faidley - do not copy or print without permission anvil rollover: [slang] A circular or semicircular lip of clouds which occurs along the underside of a back-sheared anvil. ©Warren Faidley - do not copy or print without permission approaching severe: A thunderstorm with winds of 40 to 57 mph, or hail 1/2 to 3/4 inches in diameter. ©Warren Faidley - do not copy or print without permission arcing (flashes): The bright white, blue or green flashes associated with powerlines and/or transformers being hit by a tornado, hurricane or strong winds. Spotters often look for arcing at night as an indication of tornadoes or destructive winds. ©Warren Faidley - do not copy or print without permission ARES: Amateur Radio Emergency Service. A group of amateur ham radio operators who assist in relaying severe weather information. [Also see spotter net., and storm spotter.] ©Warren Faidley - do not copy or print without permission ASOS: Automated Surface Observation System. An unmanned weather station that relays data via computer. ©Warren Faidley - do not copy or print without permission backing winds: Generally, winds which shift in a counterclockwise direction over a period of time at a given location. Chasers often watch surface plots for backing winds that change from south to southeasterly at the surface. This change in the direction of the winds may increase dew points, but more importantly, often create favorable veering with height of low-level winds. ©Warren Faidley - do not copy or print without permission backsheared anvil: [slang] A thunderstorm anvil which spreads upwind, against the prevailing winds aloft. A backsheared anvil indicates strong anvil-level divergence and intense updrafting. Generally associated with severe storms. ©Warren Faidley - do not copy or print without permission back-door cold front: A cold front that advances in a more east-to-west manner as opposed to the more common west-to-east or north-to-south direction. ©Warren Faidley - do not copy or print without permission ball lightning: See lightning. ©Warren Faidley - do not copy or print without permission barber pole: [slang] A vertical storm tower having the appearance of being twisted like a barber's pole. This type of structure is usually indicative of a strong, rotating updraft. ©Warren Faidley - do not copy or print without permission barometer: An instrument used to measure air pressure. ©Warren Faidley - do not copy or print without permission barometric pressure: Same as air pressure. ©Warren Faidley - do not copy or print without permission bead lightning: See lightning. ©Warren Faidley - do not copy or print without permission bear's cage: [slang] A dangerous region of a thunderstorm where storm-scalerotation is obscured by heavy precipitation. The term is often used to describe the hazard of chasing in such an area. [Also see core punch and mesocyclone.] ©Warren Faidley - do not copy or print without permission beauty light: The flat, soft light that occurs shortly before or after sunset or sunrise. This light, or glow, is favored by photographers for its golden, warm tones and lack of harsh contrast. ©Warren Faidley - do not copy or print without permission beaver tail: [slang] A low, flat cloud often shaped like a beaver's tail, located near the inflow region of a thunderstorm. ©Warren Faidley - do not copy or print without permission blue box: [slang] A severe thunderstorm watch box. Also called "blue watch." ©Warren Faidley - do not copy or print without permission blue jet: See lightning. ©Warren Faidley - do not copy or print without permission "bolt from the blue": An unexpected lightning bolt, generally associated with a lightning strike occurring several miles away from the parent storm -- seemingly coming "out of the blue." There is no scientific evidence of lightning originating from the (non-convective) clear "blue sky." Lightning has occurred with smoke clouds, nuclear explosions, volcanic eruptions, snow storms and on rare occasions, dust storms. Also see lightning. ©Warren Faidley - do not copy or print without permission bomb: 1. Any explosively developing thunderstorm or cyclone. 2. An intense, rapidly developing storm over the ocean, especially in the North Atlantic and North Pacific Oceans. ©Warren Faidley - do not copy or print without permission boundary layer: Generally, a layer of air residing in the lowest one-half mile of the atmosphere. It is within this area that winds (such as the LLJ) are affected by friction with the earth's surface and temperatures are most strongly affected by daytime insolation and nighttime radiational cooling. ©Warren Faidley - do not copy or print without permission bow echo: A radar term used to describe a bow-shaped line of thunderstorm cells. Bow echoes often produce strong and damaging straight-line winds. ©Warren Faidley - do not copy or print without permission box: [slang] A geographical area of the United States outlined for the possibility of severe weather. Boxes are issued for tornado and severe thunderstorm watches. Also called watch box. ©Warren Faidley - do not copy or print without permission bubble high: Same as mesohigh. ©Warren Faidley - do not copy or print without permission bust: [slang] An inaccurate forecast or an unsuccessful storm chase. This term also refers to situations in which severe weather is expected but does not occur. ©Warren Faidley - do not copy or print without permission cap: A layer of warm air sometimes found around 4,000 to 12,000 feet above the surface. The cap, or "capping inversion," can completely suppress or delay thunderstorm development by preventing parcels of air from rising. A favorable chase scenario occurs when the atmosphere is unstable and a strong, but breakable cap inhibits widespread storm development until a strong cumulonimbus tower "breaks the cap," rapidly developing into a supercell(s) which dominates the atmosphere. [Also see loaded gun.] ©Warren Faidley - do not copy or print without permission CAPE: See Convective Available Potential Energy. ©Warren Faidley - do not copy or print without permission carousel event: [slang] A rare tornadic event where two or more separate tornadoes revolve around each other in a carousel-type fashion. Tornadoes from a carousel event are sometimes referred to as satellites. ©Warren Faidley -- If you have ptinted this page without permission -- you are committing a felony copyright violation! This page is watermarked for security Cb: See Cumulonimbus cloud. ©Warren Faidley - do not copy or print without permission CB: Citizens Band radio (26.965 MHz to 27.405 MHz). A radio system used extensively by truckers and some chasers to relay information and cross-talk. Due to the lack of transmitting power (usually less than three miles), CB radio is not considered a reliable form of communication. [Also see ham radio.] ©Warren Faidley - do not copy or print without permission cell: Convection in the form of a single updraft, downdraft, or updraft/downdraft couplet. For example, a towering cumulus cloud or precipitation shaft. The term is also used figuratively to describe a storm echo on radar. A typical thunderstorm consists of multiple cells. [Also see supercell, multicell, multi-line, mature stage and single cell.] ©Warren Faidley - do not copy or print without permission CG: Cloud-to-Ground lightning. Made up of negative and positive charges. [Also see lightning.] ©Warren Faidley - do not copy or print without permission chaos theory: The theory that weather (and other natural systems) are ultimately unpredictable, because initial conditions can never be perfectly specified. ©Warren Faidley - do not copy or print without permission chase distance/time compression: The phenomenon that sometimes occurs after years of chasing over the same highways, where the time involved with extremely long distance driving seems to become compressed. Such compression can make long journeys tolerable. ©Warren Faidley - do not copy or print without permission chase fever: [slang] The anxious, excited feeling that most hard-core chasers have as the spring chase season approaches. ©Warren Faidley - do not copy or print without permission chase groupie or fan: [slang] A person who is obsessed with severe weather, storm chasing and/or chasers. Generally, a chase groupie does not actually chase. Groupies are not necessarily obsessed in a negative manner. Some are people who are afraid to chase, while others are unable to chase because of physical or economic reasons. ©Warren Faidley - do not copy or print without permission chase season(s): The primary periods for chasing severe weather. Tornadoes: Mid-April through mid-June in the Plains. Lightning: mid-July through mid-September in the desert southwest. Hurricanes: mid-August through mid-October in the Gulf of Mexico and east coast regions. ©Warren Faidley - do not copy or print without permission chaser convergence: [slang] The convergence of storm chasers in the vicinity of the most promising storms, or a pre-storm invasion of a small town. ©Warren Faidley - do not copy or print without permission chaser vertigo and/or fatigue: [slang] A sometimes dangerous condition most commonly caused by fatigue, eyestrain, dehydration or low blood sugar. Chaser vertigo may include disorientation, headaches and sightnings of mirages such as pseudo storm towers on the horizon or ghost vehicles in the passing lane. ©Warren Faidley - do not copy or print without permission chaser's caravan: [slang] A group of four or more chase vehicles actively engaged in intercepting a storm. "Caravanning" of large groups is generally frowned upon by experienced chasers, because it can be unsafe and draw unwanted attention. Large groups of vehicles may have trouble finding safe parking along highways and long lines of vehicles can be difficult to pass. If an accident occurs within a line of vehicles, both lanes may be blocked and escape routes blocked. ©Warren Faidley - do not copy or print without permission chaser's flack: [slang-Faidley] Hailstones, especially those hitting a chase vehicle! [Also see souvenirs.] ©Warren Faidley - do not copy or print without permission chaser's neck: [slang-Faidley] A sore, stiff neck caused by excessive head turning while chasing storms. Similar to the neck strains experienced by fighter pilots. ©Warren Faidley - do not copy or print without permission chaser's penalty: [slang-Moller] The price, i.e., time, money, frustration, that a chaser pays for traveling hundreds of miles without seeing a storm because of an inaccurate forecast or inexperience. ©Warren Faidley - do not copy or print without permission chaser's withdrawal: [slang] A depressed feeling chasers develop during the off-season, especially in the winter. ©Warren Faidley - do not copy or print without permission CHQ: [slang-Faidley] Chasers Headquarters. A motel, apartment or other building used as a temporary chase operations center while traveling away from home. Chubasco: A Spanish term used for any brief, heavy rainstorm or thunderstorm. ©Warren Faidley - do not copy or print without permission cirrus (Ci): High clouds consisting of ice crystals, found at altitudes of 16,000 feet or higher. Cirrus clouds often appear as white feathery streaks, or narrow white bands or patches. Thunderstorm anvils are a form of cirrus. A widespread, thick layer of cirrus may inhibit surface heating, which can delay or suppress storm development. ©Warren Faidley - do not copy or print without permission cirrus streak: A narrow cirrus cloud band associated with a jet stream or jet streak. ©Warren Faidley - do not copy or print without permission classic supercell: A type of supercell storm. A supercell with a precipitation-free region of rotation and heavy precipitation in the forward-flank.. Most chasers prefer this type of storm, because tornadoes are generally produced from a precipitation-free, wall cloud area, as opposed to high-precipitation supercells. [Compare with high-precipitation and low-precipitation supercells.] ©Warren Faidley - do not copy or print without permission clear slot: An area of clearing skies or cloud cover, often indicating an intrusion of drier air, applying to either storm-scale or synoptic-scale features. On the storm-scale, clear slots are often seen as clearing cloud material near the southern region of an occluding updraft. ©Warren Faidley - do not copy or print without permission closed eye wall: A well-structured hurricane eye wall with no gaps or deformities. A closed eye wall may denote a strong or strengthening storm. [Compare with open eye wall.] ©Warren Faidley - do not copy or print without permission closed low: A low pressure area completely circled by isobars. [Compare with open trough.] ©Warren Faidley - do not copy or print without permission cloud tags: See fractus clouds. ©Warren Faidley - do not copy or print without permission cold air advection: The transport of cold air into a region by horizontal winds. Such advection aloft can assist in destabilization. ©Warren Faidley - do not copy or print without permission cold air funnel: A funnel cloud or usually weak tornado that forms from a thunderstorm, rain shower or cumulus cloud in environments where the air aloft is unusually cold or in rain-cooled air. ©Warren Faidley - do not copy or print without permission cold front: A zone where a cold air mass advances and replaces a warm air mass. Storms may form along or slightly ahead of the boundary, due to the increased instability caused by layer lifting associated with the front. ©Warren Faidley - do not copy or print without permission cold pool: Synoptic-scale: An area of cold air in the mid-troposphere that can increase instability. Storm-scale: a precipitation-cooled area left in the wake of a thunderstorm, which can inhibit further storm development. ©Warren Faidley - do not copy or print without permission collar cloud: A circular cloud ring which often surrounds the upper part of a wall cloud. ©Warren Faidley - do not copy or print without permission Colorado low: A surface low pressure area which forms over the eastern slopes of the Rocky Mountains. Such lows enhance the severe weather potential in the Plains if other elements are present. ©Warren Faidley - do not copy or print without permission comma cloud: A synoptic-scale, comma-shaped cloud pattern. Comma clouds are often seen on satellite images in association with low pressure systems, or cyclones. ©Warren Faidley - do not copy or print without permission comma echo: A radar term used to describe the comma-shaped top portion of a bow echo. ©Warren Faidley - do not copy or print without permission convection: The vertical transport of moisture and heat by updrafts and downdrafts, sometimes as thunderstorms but most commonly as convection currents. ©Warren Faidley - do not copy or print without permission convective available potential energy (CAPE): A measure of the amount of energy available for convection. The CAPE is directly related to the maximum potential vertical speed within an updraft. Higher values may indicate a greater potential for severe weather. CAPE is measured from thermodynamic profiles of the atmosphere called soundings. ©Warren Faidley - do not copy or print without permission convective outlook: See anticipated convective outlook.. ©Warren Faidley - do not copy or print without permission convective temperature: The approximate temperature to which surface air must be warmed in order to eliminate the stable surface layer. [See cap.] ©Warren Faidley - do not copy or print without permission convergence: A directional merging or piling up of winds that can result in upward forcing, assisting in storm development. ©Warren Faidley - do not copy or print without permission core: The area of a thunderstorm, usually located in the forward- or rear-flank downdrafts, which contains the heaviest rain and the largest hail. Also refers to the center of a tornadic vortex. ©Warren Faidley - do not copy or print without permission core punching, plunge: [slang] A penetration by a vehicle into the core of a storm. Core punching is an extremely dangerous maneuver that places the chaser in the heaviest precipitation (rain and large hail) areas of the storm. Core punching is also hazardous because tornadoes can be embedded in, or around, the core. ©Warren Faidley - do not copy or print without permission Coriolis Effect: The effect caused by the rotation of the earth that deflects any free moving object (such as wind) to the right of its path in the Northern Hemisphere. The deflection is greater the faster the wind motion and the longer the air parcel is in motion. This effect is significant at the larger scales but has been shown to be relatively unimportant in tornadogenesis. ©Warren Faidley - do not copy or print without permission corkscrew: [slang] A term used to describe the twisting motion in a convective tower, often seen as cloud striations or abarber pole effect. Implies rotation within the storm. ©Warren Faidley - do not copy or print without permission crepuscular rays: Shafts or beams of light sometimes seen when the sun moves behind clouds. The rays are most pronounced during sunset or sunrise. Also called "Jesus rays." ©Warren Faidley - do not copy or print without permission CS: [slang-Faidley] Cloud-to-structure lightning. [Also see lightning.] ©Warren Faidley - do not copy or print without permission Cu: Cumulus cloud. ©Warren Faidley - do not copy or print without permission cumulonimbus (Cb): A cloud, associated with thunderstorms, characterized by a strong vertical development in the form of huge, cauliflower-like towering clouds, usually topped by an anvil cloud. Also called "thunderhead." ©Warren Faidley - do not copy or print without permission cumulus (Cu): Detached, low-level clouds, generally found at less than 6,000 feet, often appearing as mounds or domes with sharp outlines. [Also see towering cumulus.] ©Warren Faidley - do not copy or print without permission cumulus field: A large area of cumulus clouds. Chasers will often watch these areas of vertical cloud growth for the development of storms. A significant cumulus field within a capped region is often a sign that the cap may be ready to break. ©Warren Faidley - do not copy or print without permission curtains: Veils, streaks or heavy shafts of falling rain and/or hail. ©Warren Faidley - do not copy or print without permission cutoff low: A closed area of low pressure aloft that has become completely detached from the main, westerly wind flow. ©Warren Faidley - do not copy or print without permission cyclic storm: A thunderstorm that goes through cycles of intensification and weakening while maintaining its individuality. Many supercells are cyclic, which allows them to produce multiple tornadoes. A thunderstorm that undergoes only a single cycle is called a pulse storm. ©Warren Faidley - do not copy or print without permission cyclogenesis: The process by which a new cyclone is created, or the process that causes the intensification of a pre-existing cyclone. ©Warren Faidley - do not copy or print without permission cyclone: Any low pressure area associated with winds circulating counterclockwise (in the Northern Hemisphere as seen from above). The two main types of cyclones are extratropical and tropical. The term cyclone was once used to describe tornadoes. ©Warren Faidley - do not copy or print without permission cyclonic rotation: Rotation in a counterclockwise direction (in the Northern Hemisphere as seen from above). The opposite of anticyclonic rotation. ©Warren Faidley - do not copy or print without permission D through F Editors note: When quoting directly from this glossary, please credit as follows: ©Warren Faidley/Stormchaser.com Warning! This glossary is provided as a courtesy for educational, safety and reference use only. The text is protected by a ©US Copyright. Single terms may be quoted as references for editorial and educational use. Do not copy, print-out or reproduce the overall text without expressed written permission and licensing from Warren Faidley. Internet users may link to this glossary, but it cannot be copied and placed on webpages. Printed copies of this glossary will be available soon.