Turbulence - Any irregular or disturbed flow in the atmosphere caused by eddies and vertical air currents. Regions of the atmosphere that are characterized by turbulence will often be found in the vicinity of frontal boundaries. Thunderstorms produce the most severe turbulence due to the intense upward and downward vertical air currents that occur in the vicinity of them.

Rain Gauge - An instrument used to measure the amount of rainfall that occurs over a specific site. A standard rain gauge can measure up to 8 inches. The first known device that was used for measuring rainfall was invented in Korea in 1441.

Hadley cell - A thermally driven air circulation in tropical and subtropical latitudes of both hemispheres. The Hadley cell resembles a huge convective cell with rising air near the equator and sinking air in the subtropical latitudes. This concept was first introduced by George Hadley in 1735.

Parhelion (Sun dog) - The scientific name for sun dogs. This phenomenon is seen as two colored luminous spots that appear at roughly 22 degrees on both sides of the sun at the same elevation. They are caused by the refraction of sunlight passing through ice crystals. They are most commonly seen during winter in the middle latitudes and are exclusively associated with cirriform clouds. They are also known as mock suns.

METAR - METAR is an acronym for Meteorological Terminal Aviation Routine Weather Report. It's an international code used for reporting, recording, and transmitting weather observations. This protocol organizes the data in a specific format and ordering for each official weather observation that is taken around the world.

Flood - A condition that occurs when water overflows the natural or artificial confines of a stream, river, or drainage ditch. Any ponding of water on what is normally dry land is also considered a flood. Floods can occur within minutes or hours of an excessive rainfall.

Scintillation - The apparent twinkling of a star due to its light passing through regions of differing air densities in the atmosphere. This results in the light being refracted and scattered before it reaches the viewer.