Winds from the four cardinal points of the compass; that is, north, east, south, and west winds.

A graphical representation of a frequency distribution. The range of the variable is divided into class intervals for which the frequency of occurrence is represented by a rectangular column. The height of the column is proportional to the frequency of ob ...

Radio Direction Finder.

Cathode Ray Tube. A display element, consisting of a vacuum tube and screen, used with computers.

An aneroid barograph designed to record atmospheric pressure variations of very small magnitude.

National Centers for Environmental Prediction. Central computer and communications facility of the National Weather Service; located in Washington, DC.

Integrated Flood Observing and Warning System. National Weather Service flood warning program.

A graphical aid used in fire weather forecasting to calculate the degree of forest-fire danger (or burning index). Commonly in the form of a circular slide rule, the firedanger meter relates numerical indices of (a) the seasonal stage of foliage, (b) the ...

Facing away from the wind.

Wind with a speed between 4 and 6 knots (4 and 7 mph), Beaufort scale number 2.

Precipitation composed of balls or irregular lumps of ice with diameters between 5 and 50 mm.

The lowest value of a measured quality at which a sensor responds. Compare to tracking.

An anemometer which derives wind speed from measurements of dynamic wind pressures. Wind blowing into a tube develops a pressure greater than the static pressure, while wind blowing across a tube develops a pressure less than the static. This pressure dif ...

Situated on the side from which the wind blows.

A hygrometer which includes an arrangement for the time recording of atmospheric humidity.

A wooden enclosure about sixteen feet square and eight feet high with a precipitation gauge at its center. The function of the fence is to minimize eddies around the gauge and thus insure a catch that is representative of the actual rainfall or snowfall.

An instrument developed by K. Angstrom for measuring the effective terrestrial radiation. It consists of four manganin strips, of which two are blackened and two are polished. The blackened strips are allowed to radiate to the atmosphere while the polishe ...

See constant-level balloon.

In physics, any process in which the flux density (or power, amplitude, intensity, illuminance, etc.) of a "parallel beam" of energy decreases with increasing distance from the source. Attenuation is always due to the action of the transmitting medium its ...

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