Anvil - The top part of a thunderstorm that spreads out across the sky. It usually spreads in all directions, but due to the upper level wind flow most of the anvil spreads in the direction of the upper level winds. Anvils occur with severe and strong thunderstorms as the air rising in the updraft reaches the equilibrium level.
Air mass Thunderstorm - A thunderstorm not associated with a front. Air mass thunderstorms typically are associated with warm, humid air in the summer months; they develop during the afternoon in response to afternoon heating by the sun, and dissipate rather quickly after sunset. Generally, they are less likely to be severe than other types of thunderstorms.
Arcus Cloud - A low, horizontal cloud formation associated with a thunderstorm's outflow. The air from a thunderstorm can fan out in 360º. So, a cloud formed from this rush air can be in the shape of a smooth curve.
Bow Echo- A radar signature formed by a line of thunderstorms where the line bulges outward into a bow shape. Damaging winds often occur near the center of the bow echo but can occur anywhere along the bowing line. Thunderstorms that form a bow echo are usually moving at a rapid pace of at least 40 mph. It is rare, but bow echoes can produce brief tornadoes. This can occur at either end of a bow echo, but most likely in the left (usually northern) end, where the circulation shows cyclonic rotation.
Cap - A layer of warm air, sometimes several thousand feet above the surface. A cap will suppress or delay the development of thunderstorms by preventing unstable air near the surface from rising past the cap. A cap, also called a "lid" sometimes, can be broken if the air near the surface becomes unstable enough to rise past the cap or "break the cap." A cap can also be broken when cooler air aloft moves into the area of the cap. When the cap is "broken" explosive thunderstorm development can result.
Cold Air Funnel - A funnel cloud that can develop from an elevated shower or thunderstorm when the air aloft is unusually cold (hence the reference to "cold air"). Since cold air funnels develop from an elevated storm they rarely touchdown. If that happens the result will be a small, relatively weak tornado.
Convection - The vertical transport of heat and moisture, especially by updrafts and downdrafts in unstable air. Showers and thunderstorms are forms of convection. The more unstable the atmosphere the greater the convection will be and the more likely the resulting storms can become severe.
Derecho - A widespread and usually fast-moving severe windstorm associated with a squall line usually containing a bow echo. Derechos can produce damaging winds over areas hundreds of miles long and more than 100 miles across. The length of time the severe winds last can be particularly damaging. While a severe thunderstorm may produce severe wind gusts that last for several minutes at a point location, derecho wind can last 30 minutes or longer.
Downdraft - The portion of a thundertorm that contains rain and hailstones and produces wind. When downdrafts are strong enough they can produce downbursts. If a thunderstorm is an engine, then the downdraft is the exhaust system. It is opposite the updraft.
Dust Devil - A small atmospheric vortex not associated with a thunderstorm, which is made visible by a rotating cloud of dust or debris (dust whirl). Dust devils form in response to surface heating during fair, hot weather. They are most frequent in arid or semi-arid regions such as Texoma. Very rarily do dust devils creat any type of damage.
Eye - A region in the center of a hurricane (tropical storm) where the winds are light and skies are clear to partly cloudy due to an area of sinking air.
Eye Wall - A wall of dense thunderstorms that surrounds the eye of a hurricane. This is where the most intense winds of a hurricane occur.
Flash Flood - A flood which is caused by heavy or excessive rainfall in a short period of time, generally less than 6 hours.
Flood - The filling with water of a normally dry area of land caused by an increased water level in a stream, river or drainage ditch or by the ponding of rainwater.
Flood Warning - Flooding has been reported or is imminent. Take the necessary precaution if you are in a flood prone area. This can be issued by the National Weather Service for either Flash Flooding, Area Flooding, or River Flooding
Flood Watch - Issued by the National Weather Service before an actual flooding event is expected to occur. Flooding of streets, roads, the area in general, creeks, streams, and/or rivers will be possible within the watch area during the time frame of the Flood Watch. Sometimes this is called a Flash Flood Watch to indicate the possibility of rapidly rising water and flooding on streets, underpasses, in ditches, and around storm drains.
Gustnado - Yes, it is a real term although its origin is slang. It is a small, relatively weak spinning column of air that resembles a tornado and can occur with supercell thunderstorms that spawn tornadoes. They are usually short-lived and occur along the gust front of a thunderstorm. While they may be considered weak, gustnados can produce some damage.
Hail - Balls or chunks of ice larger than 1/4 inch in diameter which are produced due to strong updrafts in thunderstorms. Hailstone sizes are typically estimated comparing the size of the stones to coins (dime, nickel, quarter, half-dollar, etc.) or sports balls (ping pong, golf, baseball, softball, etc.). 3/4 inch or penny-sized denotes severe hail.
High Wind Warning - A warning for sustained surface winds greater than 40 mph lasting more than an hour or winds over 58 mph over land that are either predicted or occurring for an unspecified period of time.
Hurricane - A severe tropical cyclone having winds in excess of 64 knots (74 mph).
Hurricane Warning - Hurricane conditions are expected within 24 hours. Complete all storm preparations and evacuate if directed by local officials.
Hurricane Watch - Hurricane conditions (heavy rain, tidal flooding, and winds above 75 mph) are possible within 36 hours. Prepare to take immediate action in case a warning is issued.
Inversion - Usually used in reference to temperature. It is an increase in temperature with height (which in the reverse of what usually occurs in the atmosphere). An inversion can act like a Cap (see above) and either prohibit severe weather or enhance it.
Lapse Rate - The rate of change of an atmospheric variable, usually temperature, with height. A steep lapse rate implies a rapid decrease in temperature with height (a sign of instability) and a steepening lapse rate implies that destabilization is occurring.
Lifted Index (or LI) - A common measure of atmospheric instability. The value is obtained by computing the temperature that air near the ground would have if it were lifted to a higher level at 500 mb (usually around 18,000) and comparing that temperature to the actual temperature at that level. Negative values indicate instability. The more negative the value, the more unstable the air.
Lightning - A visible electrical discharge produced by thunderstorms caused by an imbalance of electrons between different storm cells or between the thunderstorm and the ground.
Moisture Advection - Transport of moisture by horizontal winds. This can sustain severe and non-severe thunderstorms at night when the heat of the day is lost.
Severe Thunderstorm Warning - Issued by the National Weather Service when severe weather has been reported or is being indicated by Doppler radar. Warnings indicate imminent danger and the appropriate action should be taken. A warning is issued when a thunderstorm may produce wind gusts of or more than 58 mph and/or ¾" or larger hail.
Severe Thunderstorm Watch - An outlined area where severe thunderstorms are more likely to occur within a certain time frame. Sometimes will be referred to as a "watch box". During a watch you should stay informed and watch the weather situation closely by staying tuned to 7NEWS and your SkyWARN 7 Weather Team. Another handy tool to have during a watch is a NOAA Weather Radio.
Squall Line - A solid or nearly solid line or band of active thunderstorms.
Thunder - Thunder is produced as a sound wave. Just as friction causes noise when you rub your hands together, massive friction between neighboring air molecules produces the loud noise. The rapid expansion and subsequent contraction of air produces a sound wave that travels out from the source in all directions. Thunder is produced along the entire length of the lightning channel where air expands rapidly. This gives a prolonged thunder that lasts for several seconds. Close lightning strikes don't sound as long because the thunder sound close to you is so loud that it overpowers the sound made when the lightning channel was further away. Also, the sound waves from overhead thunder tend to curve away from a surface observer. Thunder that originates further away has a more rumbling sound to it due to reflection, scattering and damping of the noise as it moves away from the source region into low level terrain. Sometimes, thunder is not heard altogether. When more than 15 miles from the lightning discharge, the thunder will not make it to a surface observer since sound waves generally refract gradually away from the earth's surface due to the air density structure of the atmosphere.
Thunderstorm - A local storm produced by cumulonimbus clouds. It is always accompanied by lightning and thunder.
Tornado Warning - A tornado has been reported or is being indicated as possible by Doppler radar. Immediate action should be taken for you safety. Follow the DUCK Rule. Downstairs, Underneath Something, Center Part of House, Keep Away from Windows.
Tornado Watch - An outlined area where tornadoes and severe thunderstorms are more likely to occur within a certain time frame. Sometimes will be referred to as a "watch box". During a tornado watch you should stay informed and watch the weather situation closely by staying tuned to 7NEWS and your SkyWARN 7 Weather Team. Another handy tool to have during a tornado watch is a NOAA Weather Radio.
Tropical Depression - A tropical cyclone in which the maximum 1-minute sustained surface wind is 38 mph or less. They form from a tropical wave or tropical disturbance.
Tropical Disturbance - A discrete system of apparently organized convection originating in the tropics or subtropics, having a non-frontal migratory character and maintaining its identity for 24 hours or more.
Tropical Storm - A tropical cyclone in which the 1-minute sustained surface wind ranges 39-73 mph. Tropical storms pose a threat to life and/or property in coastal areas.
Tropical Storm Warning - Tropical storm force winds are occurring or are expected within 24 hours.
Tropical Storm Watch - Tropical storm force winds between 37 and 74 mph are possible in the next 36 hours.