Narrowband Data - the collection of data products transmitted from the a WSR-88D RPG to a PUP or to a NIDS vendor for external distribution

NCAR - acronym for National Center for Atmospheric Research in Boulder, CO

NCEP - acronym for National Centers for Environmental Prediction; the modernized version of NMC

NDVI (Normalized Difference Vegetation Index)- an index produced using AVHRR data from NOAA polar orbiting satellites. The index is used for monitoring vegetation changes over large areas with a resolution up to 1 km.

Near-Infrared Radiation - a type of electromagnetic radiation having a slightly higher wavelength than visible radiation

Negative-Tilt Trough - an upper level system which is tilted to the west with increasing latitude (i.e., with an axis from southeast to northwest); often it is a sign of a developing or intensifying system

Net Solar Radiation - the difference between the downward and upward fluxes of solar radiation

Net Terrestrial Radiation - the difference between the downward and upward fluxes of the terrestrial radiation fluxes

NEXRAD (NEXt-Generation Weather RADar) - network of high-resolution Doppler radars operated by the NWS; NEXRAD units are known as WSR-88D

NGM (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

NIDS - an acronym for NEXRAD Information Dissemination Service, which is a system whereby four commercial vendors have the exclusive right to distribute a certain subset of NEXRAD products to agencies outside the DoD, NWS, and FAA

Nimbostratus - a gray colored and often dark cloud, accompanied by more or less continuously falling rain, snow, sleet, etc. and not by lightning, thunder, or hail

Nitrogen - a colorless, tasteless, odorless gas that constitutes 78% of the atmosphere by volume and occurs as a constituent of all living tissues in combined form

NMC - acronym for the National Meteorological Center near Washington, D.C.; now known as NCEP

NOAA - acronym for the National Oceanographic and Atmospheric Administration

Nocturnal Radiation - see effective terrestrial radiation

Non-Coherent Radar - a conventional radar in which the phase of the transmitted radiation is not known

Northern Lights - see Aurora Borealis

Nowcasting - short-term weather forecasting for the near future, generally from minutes up to a few hours in the future

NSSFC - acronym for the old National Severe Storms Forecast Center in Kansas City, MO; now the Storm Prediction Center in Norman, OK

NSSL - acronym for National Severe Storms Laboratory in Norman, OK

Numerical Weather Prediction (NWP) - the forecasting of the evolution of atmospheric disturbances by computational methods on a computer

NWP - acronym for Numerical Weather Prediction; see Numerical Weather Prediction

NWS - acronym for National Weather Service

Nyquist Velocity - see maximum unambiguous velocity