Clouds which cover between 6/10 and 9/10 of the sky. See Sky Terminology.

The height ascribed to the lowest layer of clouds or obscuring phenomena when it is reported as broken, overcast, or obscuration and not classified as "thin" or "partial." The ceiling is termed unlimited when these conditions are not satisfied. ...

A unit of luminance (or brightness) equal to 1/6 candles per square centimeter.

A set of rules or conventions used to standardize data transfer between devices.

Same as mirror nephoscope.

Reduction of visibility by strong winds blowing across dry ground with little or no vegetation. Visibilities of 1/8 mile or less over a widespread area are criteria for a Blowing Dust Advisory.

The direction from which the wind is blowing, measured in points of the compass or in azimuth degrees.

The direction, with respect to true north, from which the wind is blowing. Distinguish from magnetic wind direction. In all standard upper-air and surface weather observations, it is true wind direction that is reported.

A thermograph in which ventilation is provided by a suction fan.

A small balloon used to determine the height of the cloud base. The height can be computed from the ascent velocity of the balloon and the time required for its disappearance into the cloud.

A photometric unit of illuminance or illumination equal to one lumen per square meter

A precipitation amount of less than 0.005 inches. Also, the record made by any self-registering instrument.

A medium-sized instrument shelter. It is a white louvered box with a flat double to of and is mounted four feet above the ground on a four-legged stand.

Fine dust or salt particles dispersed through a portion of the atmosphere; a type of lithometer. The particles are so small they cannot be felt or seen with the naked eye. Many haze formations are caused by the presence of an abundance of condensation nuc ...

The water portion of the earth as distinguished from the solid part, called the lithosphere, and from the gaseous outer envelope, called the atmosphere.

See gust and peak gust.

Graduated fixed stake used in regions of abundant snowfall to facilitate the measurement of snow depth.

See stage.

A type of atmometer. It is a pan used in the measurement of the evaporation of water into the atmosphere. The NWS Class A pan is a cylindrical container 48 inches in diameter and 10 inches deep.

Precipitation of white, opaque, spherical or conical ice particles that are crisp and easily crushed and that have diameters of 2 to 5 mm.