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Mauna Kea Weather Center Meteorology Glossary/Dictionary

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  • N weather - (Obsolete.) Abbreviation for instrument weather.

  • NAT - See nitric acid trihydrate.

  • NEC - Abbreviation for North Equatorial Current.

  • needle - See ice needle.

  • network - System of small and mottled areas of enhanced brightness in the solar chromosphere. Their size varies from 5 to 20 arc-seconds. These features evolve from the plage areas and, like the plage, their number and intensity varies with the solar cycle. Also referred to as enhanced network, active network, and bright network.

  • night wind - Dry squalls that occur at night in southwest Africa and the Congo. It is likely that this term is loosely applied to other diurnal local winds such as mountain wind, land breeze, midnight wind, etc.

  • NOAA - An operational series of meteorological satellites, named for the National Oceanic and Atmospheric Administration. See POES.

  • normal - 1. Referring to a normal distribution. 2. Regular or typical in the sense of lying within the limits of common occurrence, but sometimes denoting a unique value, as a measure of central tendency. Either sense presupposes a stable probability distribution. 3. As usually used in meteorology, the average value of a meteorological element over any fixed period of years that is recognized as a standard for the country and element concerned. Often erroneously interpreted by the general public as meaning the weather patterns that one should expect. In the broadest sense, "normals" should consist of a suite of descriptive statistics, including measures of central tendency (e.g., mean, median), range (e.g., standard deviation, interquartile range, extremes), variation, and frequency of occurrence. At the International Meteorological Conference at Warsaw in 1935, the years 1901-30 were selected as the international standard period for normals. Recommended international usage is to recalculate the normals at the end of every decade using the preceding 30 years. This practice is used to take account of the slow changes in climate and to add more recently established stations to the network with observed normals. Normals should be based on actual observations if available; otherwise a recognized method should be used to "reduce" shorter series to the normal period by comparison with neighboring stations. Recognized methods of adjusting for inhomogeneities should be used to account for breaks or gradual changes introduced into the data record by changes in the hours of observation, in the observational practices, in the site or instruments used, or by a gradual change in the character of the surrounding country, such as the growth of a city. The years covered by a normal should always be clearly stated, since averages for different periods of the same length are rarely the same. See climatological standard normals.

  • northeaster - (Commonly contracted nor'easter.) A northeast wind, particularly a strong wind or gale. Two well-known examples are the black northeaster of Australia and New Zealand and the northeast storm of the east coast of North America.

  • norther - A northerly wind; in general, a cold windstorm from the north. The term has several specific applications: 1) In the southern United States, especially in Texas (Texas norther), in the Gulf of Mexico, in the Gulf of Panama away from the coast, and in Central America (norte), the norther is a strong cold wind from between northeast and northwest. It occurs between November and April, freshening during the afternoon and decreasing at night. It is a cold air outbreak associated with the southward movement of a cold anticyclone. It is usually preceded by a warm and cloudy or rainy spell with southerly winds. The norther comes as a rushing blast and brings a sudden drop of temperature of as much as 25°F in one hour or 50°F in three hours in winter. 2) The California norther is a strong, very dry, dusty, northerly wind that blows in late spring, summer, and early fall in the valley of California or on the West Coast when pressure is high over the mountains to the north. It lasts from one to four days. The dryness is due to adiabatic warming during descent. In summer it is very hot. 3) The Portuguese norther is the beginning of the trade wind west of Portugal. 4) Norther is used for a strong north wind on the coast of Chile that blows occasionally in summer. 5) In southeast Australia, a hot dry wind from the desert is called a norther. See also chocolatero, tehuantepecer; compare burster, pampero.

  • northwester - (Often contracted nor'wester.) A northwesterly wind (as Canterbury northwester). See also kal Baisakhi.

  • NOy - See total reactive nitrogen.

  • nT - The nanotesler (nT); a measure of geomagnetic field strength. There are 109 nanoteslers in a tesler, which is the unit of measure of magnetic field strength in the SI system of units. An nT is equal to a gamma. There are 105 gammas in an oersted, which is the unit of measure of magnetic field strength in the cgs system.