Measure of the water vapor content of the air.
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.
Air that flows into a thunderstorm.
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 [...]
(LFC) the level at which a parcel of saturated air becomes warmer than the surrounding air and begins to rise freely. This occurs most readily in a conditionally unstable atmosphere.
See Level of Free Convection
Air parcels rising up from the ground or some other surface
Or Lifting Condensation Level (LCL). The level at which a parcel of moist air becomes saturated when it is lifted dry adiabatically.
(LI) A common measure of atmospheric instability. Its value is obtained by computing the temperature that air near the ground would have if it were lifted to some higher level (around 18,000 feet, usually) and comparing that temperature to the actual temperature at that level. Negative values indicate instability - the more negative, the more [...]
A region of relatively strong winds in the lower part of the atmosphere. Specifically, it often refers to a southerly wind maximum in the boundary layer, common over the Plains states at night during spring and summer.
Rounded, smooth, sack-like protrusions hanging from the underside of a cloud (usually a thunderstorm anvil). Mammatus clouds often accompany severe thunderstorms, but do not produce severe weather; they may accompany non-severe storms as well.
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 [...]
Referring to weather systems smaller than synoptic-scale systems but larger than storm-scale systems. Horizontal dimensions generally range from around 50 miles to several hundred miles. Squall lines and Mesoscale Convective Systems (MCS) are examples of mesoscale weather systems
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.
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.
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
See Multicell Thunderstorm
The National Weather Service (NWS) is an agency of the United States government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the purposes of protection, safety, and general information. http://www.weather.gov/ is the National Weather Service home page.