NCEP - National Center for Environmental Prediction. Branch of the National Weather Service responsible for developing, running, and maintaining the main American computer models.

Stationary Front - A nearly stationary narrow zone of transition between contrasting air masses; winds blow parallel to the front but in opposite directions on either side of the front.

Ground clutter - Radar returns that are received from stationary ground-based targets. Most ground clutter is located 30 miles or less from the radar site, unless a temperature inversion is present. When a temperature inversion is present, the radar beam bends downward towards the earth's surface, creating ground clutter much farther away from the radar site. Common sources of ground clutter are hills, buildings, wind mills, and even wave crests at sea.

Fujita Scale or F-Rating - A scale that uses visual damage to determine the strength of a tornado. The Fujita scale was developed by Dr. Fujita in 1971 while he was conducting research at the University of Chicago. The scale goes from 0 to 5, with 0 being weak and 5 being violent. The Fujita scale was decommissioned in the US in 2007 because it didn't fully account for different structural types. The enhanced Fujita scale is now being used to rate tornadoes.

Cloud - Any visible mass of water droplets, ice crystals, or a mix of both that become suspended in the atmosphere. Fog is a cloud that forms at the ground, while cirrus clouds oftentimes form at around 40,000 feet.

Scud clouds - Low, detached clouds caught in the outflow beneath the thunderstorm. These are often mistaken for funnel clouds or tornadoes.

Zonal Flow - Large scale atmospheric flow in which air flow is almost directly from west to east.