Civil Twilight - Is defined to begin in the morning, and to end in the evening when the center of the Sun is geometrically 6 degrees below the horizon. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished. During civil twilight artificial lighting is no longer required as long as clear skis are present. Only the brightest stars and planets can be seen by the naked eye during civil twilight.

Cold Front - A narrow zone of transition between relatively cold, dense air that is advancing and replacing warmer air out ahead of it.

Rime - A white, granular, and opaque deposit of ice formed by the rapid freezing of supercooled water droplets onto a surface. Rime can accumulate to a few inches on trees and other objects when subfreezing air and fog lingers over a region for an extended period of time.

Super-Typhoon - A tropical cyclone in the western Pacific basin that has one minute sustained wind speeds of a last 150 mph. This corresponds to what would be a category 4 or greater hurricane if the tropical cyclone were in the Atlantic or eastern Pacific.

Synoptic Scale - In meteorology this refers to the study of large scale systems that develop in the atmosphere. Major cyclones and their associated fronts are a commonly studied feature in synoptic meteorology. In order to be on the synoptic scale, a system must stretch across a distance of at least 600 miles.

Rawinsonde - An instrument attached to a weather balloon that measures atmospheric pressure, temperature, humidity, and wind speed/direction at different layers of the atmosphere. As the instrument rises through the atmosphere, the data is sent via radio waves to a receiver on the ground. Rawinsondes are launched all over the world at specified times. The data from these launches is used in initializing the numerous forecast models.

isodrosotherm - A line of equal dew point temperature. Isodrosotherms are typically drawn for surface dew points. They can give meteorologists a good read on where surface fronts are located since tightly packed isodrosotherms indicate a dew point gradient.