A COMPREHENSIVE GLOSSARY OF WEATHERMichael Branick
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). A negative-tilt trough often is a sign of a developing or intensifying system.
NEXRAD - NEXt-Generation Weather RADar. Technologically-advanced weather radar being deployed to replace WSR-57 and WSR-74 units. NEXRAD is a high-resolution Doppler radar with increased emphasis on automation, including use of algorithms and automated volume scans. NEXRAD units are known as WSR-88D.
NOAA - National Oceanographic and Atmospheric Administration.
Nocturnal - Related to nighttime, or occurring at night.
Nowcast - A short-term weather forecast, generally out to six hours or less.
NSSL - National Severe Storms Laboratory, in Norman OK. (Sometimes pronounced NES-sel.)
NWP - Numerical Weather Prediction.
NWS - National Weather Service.