Aeronautical Terms beginning with H

Hail

A form of precipitation composed of balls or irregular lumps of ice, always produced by convective clouds which are nearly always cumulonimbus.

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Halo

A prismatically colored or whitish circle or arcs of a circle with the sun or moon at its center; coloration, if not white, is from red inside to blue outside (opposite that of a corona); fixed in size with an angular diameter of 22° (common) or 46° (rare); characteristic of clouds composed of ice crystals; valuable in differentiating between cirriform and forms of lower clouds.

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Hazardous Weather Information

Summary of SIGMETs, Convective SIGMETs, urgent Pilot Weather Reports (PIREP), CWAs, AIRMETs, and any other significant weather provided to pilots that might not be routinely provided in a standard format or report.

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Haze

A type of lithometeor composed of fine dust or salt particles dispersed through a portion of the atmosphere; particles are so small they cannot be felt or individually seen with the naked eye (as compared with the larger particles of dust), but diminish the visibility; distinguished from fog by its bluish or yellowish tinge.

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High

An area of high barometric pressure, with its attendant system of winds; an anticyclone. Also high pressure system.

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Humidity

Water vapor content of the air; may be expressed as specific humidity, relative humidity, or mixing ratio.

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Hurricane

A tropical cyclone in the Western Hemisphere with winds in excess of 65 knots or 120 km/h.

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Hydrometeor

A general term for particles of liquid water or ice such as rain, fog, frost, etc., formed by modification of water vapor in the atmosphere; also water or ice particles lifted from the earth by the wind such as sea spray or blowing snow.

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Hygrograph

The record produced by a continuous-recording hygrometer.

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Hygrometer

An instrument for measuring the water vapor content of the air.

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