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

Same as precipitation- effectiveness index.

Precipitation falling from a cloud, usually in wisps or streaks, but evaporating before it reaches the ground.

A reflecting type telescope with a 45

Same as ombrometer.

A small balloon whose ascent is followed by a theodolite in order to obtain data for the computation of winds aloft.

A faintly-colored circular arc similar to a rainbow but formed on fog layers containing drops whose diameters are 100 microns or less. Also called mistbow, white rainbow.

That stage, on a fixed river gauge, at which overflow of the natural banks of the stream begins to cause damage in any portion of the reach for which the gauge is used as an index.

The upward force produced by the gas in a balloon. It is equal to the free lift plus the weight of the balloon and the attached equipment.

Any quantity, such as force velocity, or acceleration, which has both magnitude and direction at each point in space, as opposed to scalar which has magnitude only. Such a quantity may be represented geometrically by an arrow of length proportional to its ...

Wind with a speed between 11 and 16 knots (13 and 18 mph); Beaufort scale number 4.

A sounding balloon which, when operationally inflated, resembles an inverted teardrop.

An instrument that shows changes in humidity.

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 ...

In radiometry, a measure of the intrinsic radiant intensity emitted by a radiator in a given direction.

A hydrometeor consisting of an aggregate of microscopic and more-or-less hygroscopic water droplets suspended in the atmosphere. It reduces visibility to a lesser extent than fog. The relative humidity of mist is often less than 95 percent.

NEXt Generation RADar. A NWS network of about 140 Doppler radars operating nationwide.

A captive balloon used to maintain meteorological equipment aloft at approximately a constant height. The kytoon is streamlined and combines the aerodynamic properties of a balloon and a kite.

An instrument for photographing the corona and prominences of the sun at times other than at solar eclipse.

Frozen or partly frozen rain.