Changes in temperature caused by the expansion (cooling) or compression (warming) of a body of air as it rises or descends in the atmosphere, with no exchange of heat with the surrounding air.
The transport of an atmospheric property such as temperature or moisture by wind.
A layer of relatively warm air aloft, usually several thousand feet above the ground, which suppresses or delays the development of thunderstorms. Air parcels rising into this layer become cooler than the surrounding air, which inhibits their ability to rise further and produce thunderstorms. Sometimes called the lid.
Convective Available Potential Energy. CAPE is directly related to the maximum potential vertical speed within an updraft; higher values indicate greater potential for severe weather.
The Climate Prediction Center (CPC) is one of the National Centers for Environmental Prediction, which are a part of NOAA's National Weather Service. It is located in College Park, Maryland. CPC issues climate forecasts valid weeks and months in advance.
A zone separating two air masses, of which the cooler, denser mass is advancing and replacing the warmer.
A forecast containing the area(s) of expected thunderstorm occurrence and expected severity over the contiguous United States, issued several times daily by the SPC. The terms marginal, slight risk, enhanced risk, moderate risk, and high risk are used to describe severe thunderstorm potential. Local versions sometimes are prepared by local NWS offices.
Tending to move toward one point or to approach each other. Convergence in a horizontal wind field indicates that more air is entering a given area than is leaving at that level. Convergence at low levels may result in upward forcing; at higher levels convergence may result in downward forcing. When other factors such as [...]
A measure of atmospheric moisture, specifically the temperature to which the air must be cooled to reach saturation, assuming constant moisture and pressure. When the air reaches dewpoint, visible drops of water form.
The changing of wind direction with height.
To split and move out in different directions from a single point, usually said of horizontal winds. Divergence at upper levels of the atmosphere enhances upward motion, and hence the potential for thunderstorm development.
Issued to indicate current or developing hydrologic conditions that are favorable for flash flooding in and close to the watch area, but the occurrence is neither certain or imminent.
A narrative statement produced by the National Weather Service, frequently issued on a routine basis by a local weather forecast office (WFO), to provide information regarding the potential of significant weather expected during the next 1 to 5 days.
A tropical cyclone in the Atlantic, Caribbean Sea, Gulf of Mexico, or eastern Pacific, which the maximum 1-minute sustained surface wind is 64 knots (74 mph) or greater.
The tendency for air parcels to accelerate when they are displaced from their original position; especially, the tendency to accelerate upward after being lifted. Instability is a prerequisite for severe weather.
Along narrow meandering current of high-speed, high-altitude winds near the tropopause blowing from a generally westerly direction and often exceeding a speed of 250 miles (402 kilometers) per hour. The position and orientation of jet streams vary from day to day. General weather patterns are related closely to the position, strength and orientation of the [...]
Air parcels rising up from the ground or some other surface
When conditions actually begin to shape up for severe weather, SPC (Storm Prediction Center) often issues a Mesoscale Discussion (MCD) statement anywhere from roughly half an hour to several hours before issuing a weather watch. SPC also puts out MCDs for hazardous winter weather events on the mesoscale, such as locally heavy snow, blizzards and [...]
At its most basic, a person who studies the science of weather. Often used to refer to professional persons who have completed a formal program of study and received a degree from an accredited educational institution in meteorology.
Thunderstorms are organized in clusters of at least 2-4 short-lived cells. Convergence along the gust front(s) causes new storms to develop every 5-15 minutes