Atmospheric instabilityAtmospheric instability is a condition where the Earth's atmosphere is considered to be unstable and as a result local weather is highly variable through distance and time. Atmospheric stability is a measure of the atmosphere's tendency to discourage vertical motion, and vertical motion is directly correlated to different types of weather systems and their severity. In unstable conditions, a lifted thing, such as a parcel of air will be warmer than the surrounding air. Because it is warmer, it is less dense and is prone to further ascent.
Weather balloonA weather balloon, also known as sounding balloon, is a balloon (specifically a type of high-altitude balloon) that carries instruments aloft to send back information on atmospheric pressure, temperature, humidity and wind speed by means of a small, expendable measuring device called a radiosonde. To obtain wind data, they can be tracked by radar, radio direction finding, or navigation systems (such as the satellite-based Global Positioning System, GPS). Balloons meant to stay at a constant altitude for long periods of time are known as transosondes.
RainbandA rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as banded structure. Rainbands within tropical cyclones are curved in orientation. Rainbands of tropical cyclones contain showers and thunderstorms that, together with the eyewall and the eye, constitute a hurricane or tropical storm.
Storm chasingStorm chasing is broadly defined as the deliberate pursuit of any severe weather phenomenon, regardless of motive, but most commonly for curiosity, adventure, scientific investigation, or for news or media coverage. A person who chases storms is known as a storm chaser or simply a chaser. While witnessing a tornado is the single biggest objective for most chasers, many chase thunderstorms and delight in viewing cumulonimbus and related cloud structures, watching a barrage of hail and lightning, and seeing what skyscapes unfold.
Fire whirlA fire whirl or fire devil (sometimes referred to as a fire tornado) is a whirlwind induced by a fire and often (at least partially) composed of flame or ash. These start with a whirl of wind, often made visible by smoke, and may occur when intense rising heat and turbulent wind conditions combine to form whirling eddies of air. These eddies can contract a tornado-like vortex that sucks in debris and combustible gases.
Convergence zoneA convergence zone in meteorology is a region in the atmosphere where two prevailing flows meet and interact, usually resulting in distinctive weather conditions. This causes a mass accumulation that eventually leads to a vertical movement and to the formation of clouds and precipitation. Large-scale convergence, called synoptic-scale convergence, is associated with weather systems such as baroclinic troughs, low-pressure areas, and cyclones.
Tornado AlleyTornado Alley is a loosely defined location of the central United States and Canada where tornadoes are most frequent. The term was first used in 1952 as the title of a research project to study severe weather in areas of Texas, Louisiana, Oklahoma, Kansas, South Dakota, Iowa and Nebraska. Tornado climatologists distinguish peaks in activity in certain areas and storm chasers have long recognized the Great Plains tornado belt.
Convective storm detectionConvective storm detection is the meteorological observation, and short-term prediction, of deep moist convection (DMC). DMC describes atmospheric conditions producing single or clusters of large vertical extension clouds ranging from cumulus congestus to cumulonimbus, the latter producing thunderstorms associated with lightning and thunder. Those two types of clouds can produce severe weather at the surface and aloft.
CyclogenesisCyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere (a low-pressure area). Cyclogenesis is an umbrella term for at least three different processes, all of which result in the development of some sort of cyclone, and at any size from the microscale to the synoptic scale. Tropical cyclones form due to latent heat driven by significant thunderstorm activity, developing a warm core. Extratropical cyclones form as waves along weather fronts before occluding later in their life cycle as cold core cyclones.
VisibilityThe visibility is the measure of the distance at which an object or light can be clearly discerned. In meteorology it depends on the transparency of the surrounding air and as such, it is unchanging no matter the ambient light level or time of day. It is reported within surface weather observations and METAR code either in meters or statute miles, depending upon the country. Visibility affects all forms of traffic: roads, railways, sailing and aviation.
