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 composite reflectivity is the maximum dBZ reflectivity from any of the reflectivity angles of the NEXRAD weather radar
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.
A powerful downdraft often associated with an intense thunderstorm that strikes the ground and deflects in all directions. A downburst may produce damaging surface winds.
The height above ground of the center of the radar beam using the tilt, or scan, that contains the highest elevation where reflectivities greater than 18 dBZ can be detected.
A rapid and extreme flow of high water into a normally dry area, or a rapid water level rise in a stream or creek above a predetermined flood level, beginning within six hours of the causative event
Issued to inform the public, emergency management, and other cooperating agencies that flash flooding is in progress, imminent, or highly likely.
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.
Any high flow, overflow, or inundation by water which causes or threatens damage.
The main region of downdraft in the forward, or leading, part of a supercell, where most of the heavy precipitation is.
The altitude at which the air temperature first drops below freezing.
Precipitation falling from a cumulonimbus cloud in the form of pellets or balls of ice greater than 5mm in diameter. Hailstones are usually composed of concentric layers of clear ice and compact snow.
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.
Air parcels rising up from the ground or some other surface
A rotating air mass within a thunderstorm which may produce a tornado, usually 2-6 miles in diameter and often found on the right rear flank of a supercell thunderstorm. On high-precipitation (HP) supercell, the mesocyclone may be found on the front flank. Although strictly speaking a radar term, a supercell may exhibit visual cues indicating [...]
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 [...]
A convective downdraft with an affected outflow area of less than 2 ½ miles wide and peak winds lasting less than 5 minutes. Microbursts may induce dangerous horizontal/vertical wind shears, which can cause property damage.