Science / Weather Glossary

Blowing Dust: Dust that is raised by the wind to heights of six feet or greater. It is reported as 'BLDU' in an observation and on the METAR.

Blowing Sand: Sand that is raised by the wind to heights of six feet or greater. It is reported as 'BLSA' in an observation and on the METAR.

Blowing Snow: Snow that is raised by the wind to heights of six feet or greater. It is reported as 'BLSN' in an observation and on the METAR.

Blowing Spray: Salt spray that is raised by the wind to heights of six feet or greater. It is reported as 'BLPY' in an observation and on the METAR.

Blue Norther: Refers to a swift-moving cold frontal passage in the southern Great Plains, marked by a dark, blue-black sky with strong wintery winds from the northwest or north and temperatures that may d . . . View Full Definition

Boiling Point: The temperature at which a liquid changes to a vaporous state. The temperature at which the equilibrium vapor pressure between a liquid and its vapor is equal to the external pressure on the . . . View Full Definition

Boulder Wind: A local name referring to an extremely strong downslope wind in the Front Range of the Rocky Mountains near Boulder, Colorado.

Boundary Layer: The lowest layer of the earth's atmosphere, usually up to 3,300 feet, or one kilometer, from the earth's surface, where the wind is influenced by the friction of the earth's surface and the . . . View Full Definition

Bow Echo: A radar echo signature often associated with severe thunderstorms, especially those that produce wind damage. It is bent outward in a 'bow' shape.

Boyles Law: States that when the temperature is held constant, the volume of a gas is inversely proportional to its pressure. Therefore, if the pressure increases, the volume decreases and visa versa. F . . . View Full Definition

Bright Band: A narrow, intense radar echo due to water-covered ice particles at the melting level where reflectivity is at its greatest.

Broken: The amount of sky cover for a cloud layer between 5/8ths and 7/8ths, based on the summation layer amount for that layer.

Bubble High: A small high that may be created by precipitation and vertical instability associated with thunderstorm activity. A product of downdrafts, it is relatively cold and often has the characteris . . . View Full Definition

Buys Ballots Law: Describes the relationship of the horizontal wind direction to the pressure distribution. In the Northern Hemisphere, if one stands with one's back to the wind, the pressure on one's left is . . . View Full Definition

Bwer: Acronym for Bounded Weak Echo Region. Refers to radar echo signatures with low reflectivity in the center, surrounded by higher reflectivity. It is associated with strong updrafts and is fou . . . View Full Definition

Calm: Atmospheric conditions devoid of wind or any other air motion. In oceanic terms, it is the apparent absence of motion of the water surface when there is no wind or swell.

Calorie: In meteorology, it is the amount of heat required to raise the temperature of one (1) gram of water one (1) degree Celsius. It is a unit of heat energy.

Cap: Composed of a layer of warmer, dryer air aloft which may suppress or delay the development of thunderstorms. As an air parcel rises, it becomes cooler relative to the ambient, or surrounding . . . View Full Definition

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