Generally a high based thunderstorm where lightning is observed, but little, if any, precipitation reaches the ground. Most of the rain produced by the thunderstorm evaporates In the relatively dry air beneath the storm. Eye level wind. This is the wind at the top of the atmospheric boundary layer which is about 3000 feet above the surface. The boundary area between two different air masses, usually where temperature, humidity, wind, and pressure are changing most rapidly with time and distance.
Colder air replaces existing warmer air in a cold front situation.
An index combining the stability and moisture content of the lower atmosphere into a number that correlates very well with large fire growth. The Haines Index is not a fire danger rating system. Thus, it should be limited to existing fires or new fire starts. One note of caution, wind is not factored into the Haines Index. Fires, especially sagebrush and grass, may become large due to strong winds even when the Index is rated low.