Appendix A: Glossary -Cont.

METEOROLOGY FLIGHT PLANNING

APPENDIX A

INTENSITY QUALIFIER Intensity qualifiers are used to describe whether a phenomenon is

light (), moderate (no symbol used), or heavy (+).

ISOBAR A line on a chart or diagram drawn through places or points having the same

barometric pressure. (Isobars are customarily drawn on weather charts to show the horizontal

distribution of atmospheric pressure reduced to sea level or the pressure at some specified

altitude.)

ISOTACH A line joining points of equal wind speed.

ISOTHERM A line on a chart or diagram drawn through places or points having equal

temperature.

LOW DRIFTING A descriptor, DR, used to describe snow, sand, or dust raised to a height of

less than six feet above the ground.

LOW DRIFTING DUST Dust raised by the wind to less than six feet above the ground;

visibility is not reduced below seven statute miles at eye level, although objects below this level

may be veiled or hidden by the particles moving nearly horizontal to the ground.

LOW DRIFTING SAND Sand raised by the wind to less than six feet above the ground;

visibility is not reduced below seven statute miles at eye level, although objects below this level

may be veiled or hidden by the particles moving nearly horizontal to the ground.

LOW DRIFTING SNOW Snow raised by the wind to less than six feet above the ground;

visibility is not reduced below seven statute miles at eye level, although objects below this level

may be veiled or hidden by the particles moving nearly horizontal to the ground.

MANUAL STATION A station, with or without an automated surface weather observing

system, where the certified observers are totally responsible for all meteorological reports that are

transmitted.

METAR/SPECI An evaluation of select weather elements from a point or points on or near the

ground according to a set of procedures. It may include type of report, station identifier, date and

time of report, a report modifier, wind, visibility, runway visual range, weather and obstructions

to vision, sky condition, temperature and dew point, altimeter setting, and Remarks.

MILLIBAR (Bar a unit of pressure equal to 1,000,000 dynes per square centimeter.) A

millibar is equal to 1/1000 of a bar.

MIST A hydrometer consisting of an aggregate of microscopic and more-or-less hygroscopic

water droplets or ice crystals suspended in the atmosphere that reduces visibility to less than six

statute miles but greater than or equal to 5/8 statute mile.

GLOSSARY A-5