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Weather Glossary - N


Nacreous cloud

Clouds that have a soft, pearly lustre and form at altitudes of around 25-30 km. Also called mother-of-pearl clouds.

Nautical mile

The distance of 1 minute of latitude. 1 nautical mile equals 1.85km.


National Centres for Environmental Prediction; the modernized version of NMC.

Negative tilt trough

An upper level system which is tilted to the east with increasing latitude (i.e., with an axis from southeast to northwest). A negative-tilt trough often is a sign of a developing or intensifying system.


NEXt-Generation Weather RADar. Technologically-advanced weather radar being deployed to replace WSR-57 and WSR-74 units in the US. NEXRAD is a high-resolution Doppler radar with increased emphasis on automation, including use of algorithms and automated volume scan. NEXRAD units are known as WSR-88D.


Nested Grid Model; one of the operational forecast models run at NCEP. The NGM is run twice daily, with forecast output out to 48 hours.


(NOGAPS) Operational forecast model run by the Fleet Numerical Meteorology and Oceanography Centre. Forecast output to 144 hours. The NOGAPS model is run primarily for operational use by the US Navy.


(Ns) Latin "nimbus" - violent rain, "stratus" - layer
A dark grey-looking cloud that often covers the entire sky. Some definitions of Nimbostratus include a required rainfall rate. Steady rain or snow generally falls from nimbostratus.


The most abundant gas in air, comprising 78% by volume. It is colourless and odourless.


National Meteorological Centre (U.S.).


National Meteorological Operations Centre (Aus). Responsible for the operation of the Australian weather service, issuing real-time analysis and prediction products, maintaining a nation-wide weather watch and support the operational communications and computing infrastructure.


National Oceanographic and Atmospheric Administration (U.S.).

Noctilucent clouds

Wavy, thin clouds that are seen at twilight in polar regions. They form at altitudes of 80-90 km and are made visible by sunlight reflecting off the underside of the cloud.


Related to night-time, or occurring at night.




A short-term weather forecast, generally out to six hours or less.


National Severe Storms Laboratory, in Norman OK, USA. (Sometimes pronounced NES-sel.)


Numerical Weather Prediction. NWP uses simplified mathematical equations of motion to simulate various processes in the atmosphere.


National Weather Service (U.S.).

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Weather News

Victorian desalination plant could be used for first time to cope with hot summer

19:22 EDT

Victoria's multi-billion-dollar desalination plant could be used for the first time, as the Andrews Government confronts a looming water crisis in drought-hit country towns.

Windy conditions to follow the warmth in QLD

17:58 EDT

Early spring warmth will come to an end as the Queensland coast is in for a breezy few days.

Tasmanian farmers say the lack of good rainfall is serious

15:50 EDT

The dry season through Tasmania's midlands, east coast and south-east is becoming a serious situation according to Coal Valley farmer, Justin Nichols.