Frontal Passage Freeze A freeze is when the surface air temperature is expected to be 32&#176F or below over a widespread area for a climatologically significant period of time. Use of the term is [..]

Downward Vertical Velocity (sinking air) DZ - Drizzle  E - East   ECMWF European Center for Medium-Range Weather Forecasting. Operational references in forecast discussions typically refer to the ECMW [..]

(usually pronounced ACK-kis) - AltoCumulus CAStellanus; mid-level clouds (bases generally 8 to 15 thousand feet), of which at least a fraction of their upper parts show cumulus-type development. These [..]

A cloud which is dependent on a larger cloud system for development and continuance. Roll clouds, shelf clouds, and wall clouds are examples of accessory clouds.

Advisory Advection Transport of an atmospheric property by the wind. See cold advection, or warm advection.

Afternoon Air-mass Thunderstorm Generally, a thunderstorm not associated with a front or other type of synoptic-scale forcing mechanism. Air mass thunderstorms typically are associated with warm, humi [..]

Rotation in the opposite sense as the Earth's rotation, i.e., clockwise in the Northern Hemisphere as would be seen from above. The opposite of cyclonic rotation.

The flat, spreading top of a Cb (cumulonimbus), often shaped like an anvil. Thunderstorm anvils may spread hundreds of miles downwind from the thunderstorm itself, and sometimes may spread upwind.

[Slang], a lightning discharge occurring within the anvil of a thunderstorm, characterized by one or more channels that appear to crawl along the underside of the anvil. They typically appear during t [..]

A large overshooting top or penetrating top.