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Glossary and Acronyms: N
NAO:
North Atlantic Oscillation.
NASA :
National Aeronautics and Space Administration (USA).
NCAR:
National Center for Atmospheric Research (USA).
NCDC:
National Climate Data Center (USA).
NCEP:
National Centers for Environmental Prediction (USA), responsible for the numerical forecasting model GFS (Global Forecast System) and MRF/AVN.
Near equatorial trough:
a broad and elongated low level cyclonic wind circulation near Equator.
Near gale:
wind with a speed between 28 and 33 knots (Beaufort scale wind force 7).
A near gale warning is a message intended to warn those concerned of the occurence or expected occurence of a wind of Beaufort force 7 over a specific area.
Near-polar orbiting satellite:
a meteorological satellite with a nearly circular, nearly polar orbit. The combination of satellite motion and the Earth's rotation beneath the orbit provides overlapping strips of satellite data covering swaths (up to 3000 km) from pole to pole. The satellite's altitude can be chosen within a wide range (600 to 1500 km) in order to provide data over the entire globe twice a day.
NESDIS:
National and Environmental Satellite Data and Information Service.
Nested grids:
grid of different spacings used in some numerical forecasting models. A fine mesh is used to give detailed information about a limited area whereas a coarse mesh is used over a larger area (often a hemisphere) to provide boundary conditions for the fine mesh calculations.
NHC:
National Hurricane Center (Miami, Floride, USA).
NMHS:
National Meteorological and Hydrological Service.
NOAA:
National Oceanic and Atmospheric Administration
(USA). Also the name of an American near-polar orbiting satellites serie of which images are useful for the tropical systems observation.
NOGAPS:
Navy Operational Global Atmospheric Prediction System (USA).
Normals :
Averages calculated over a uniform and relatively long period covering at least three consecutive ten-year periods.
North Atlantic oscillation (NAO):
The North Atlantic oscillation (NAO) is a climatic phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea-level between the Icelandic Low and the Azores high. Through east-west oscillation motions of the Icelandic Low and the Azores high, it controls the strength and direction of westerly winds and storm tracks across the North Atlantic.
The NAO was discovered in the 1920s by Sir Gilbert Walker. Unlike the El Niño phenomenon in the Pacific Ocean, the NAO is a largely atmospheric mode. It is one of the most important manifestations of climate fluctuations in the North Atlantic and surrounding humid climates.
NPOESS :
National Polar-orbiting Operational Environmental Satellite System (USA).
NRL :
Navy Research Laboratory (USA).
Numerical forecasting
(Also called mathematical forecasting, dynamical forecasting, physical forecasting, numerical weather prediction.) The integration of the governing equations of hydrodynamics by numerical methods subject to specified initial conditions.
Numerical approximations are fundamental to almost all dynamical weather prediction schemes since the complexity and nonlinearity of the hydrodynamic equations do not allow exact solutions of the continuous equations.
Numerical forecasting model :
Method of producing forecasts of meteorological fields on a computer by solving the equations of motion and other physical equations by repeated application of arithmetical operations.
NWP :
Numerical Weather Prediction.See "Numerical forecasting".
NWS :
National Weather Service (USA).