That horizontal wind velocity at which the Coriolis acceleration exactly balances the horizontal pressure force. It is directed along contour lines or isobars.

Same as water year.

An instrument of the aspiration condenser type which measures the concentration and mobility of small ions.

An instrument designed to measure quantities of heat. Sometimes used in meteorology to measure solar radiation.

See river basin.

Meteorological information issued by a watch office concerning the occurrence or forecast of weather phenomena which may affect the safety of aircraft operations.

United Kingdom forecast model. (Available via AccuWeather.com Professional.)

Old snow that has become granular and compacted as a result of melting and refreezing.

The ratios, to the mean wind speed, of the average magnitudes of the component fluctuations of the wind along three mutually perpendicular axes.

Growth of a cloud or precipitation particle by the collision and union of a frozen particle with a super-cooled water drop.

A radar which is used to obtain the azimuth elevation, and slant range of an airborne target.

A type of recording siphon barometer. The mechanically magnified motion of a float resting on the lower mercury surface is used to record atmospheric pressure on a rotating drum.

The programs and instructions which direct a computer.

The part of a measuring instrument which responds directly to changes in the environment.

A balloon designed to float at a constant pressure level. This may be accomplished by a pressure valve which controls the release of ballast so as to maintain flight above a selected pressure level until the supply of ballast is exhausted. See Moby Dick b ...

An addition to a rawinsonde system which allows determination of the slant range to the radiosonde.

A type of directional antenna used on some types of radar and radio equipment consisting of an array of elemental, single- wire dipole antennas and reflectors.

Hygrometer in which the dew (frost) point is determined by observing the temperature of an artificially cooled surface at the moment at which dew (frost) first appears on it.

A thermopile used in some types of radiation instruments. See solarimeter.

A forecast of the expected stage or discharge at a specified time, or of the total volume of flow within a specified Interval of time, at one or more points along a stream.