F FAA—Federal   Aviation   Administration. FNMOC—Fleet Numerical Meteorology and Oceanography  Center.  Located  in  Monterey, California. FULL DISK—A satellite image covering an entire hemisphere produced from a series of smaller area images. G GEOSTATIONARY—A   satellite   in   an   equatorial orbit moving in the same direction as the earth. The speed and altitude of the satellite is such that it is always located in a stable orbit over the same position  on  the  equator. GEOSYNCHRONOUS—See   geostationary. GHz—Gigahertz. Equal to one billion hertz (10⁹). GOES—GeostationaryOperational    Environmental Satellite. GROUND  CLUTTER—The pattern of radar echoes from  fixed  ground  targets. GROUND WAVE—That  portion  of  a  transmitted electromagnetic  wave  that  travels  in  the atmosphere immediately above the surface of the earth. GVAR—GOES Variable data format. H HECTOPASCAL  (hPa)—A unit of 100 pascals used to  measure  pressure,  exactly  equivalent  to  1 millibar. HERTZ—A  frequency  defined  as  one  cycle  per second. HF—High frequency. (1-3 MHz to 30 MHz.) HOOK  ECHO—A pendant or hook on the right rear of an echo that often identifies mesocyclones and tornadic activity on the radar display. HRPT—High   Resolution   Picture   Transmission, automatically  transmitted  from  polar-orbiting satellites. I INCLINATION— The angle of the orbital plane of a satellite  relative  to  the  earth’s  equatorial  plane. INFRARED (IR)—The   portion   of   the   electro- magnetic  spectrum  with  wavelengths  just  slightly longer  than  visible  light  (thermal  energy). INVERSION—With   respect   to   temperature,   an increase in temperature with height. Normally, temperature  decreases  with  height  in  the atmosphere. K kHz—Kilohertz. Equal to one thousand hertz (10³). kn—Alternate abbreviation for knot. In meteorology, the more frequently used abbreviation is "kt," but this should not be confused with the uppercase "KT"  meaning  kiloton. L LINE ECHO WAVE PATTERN (LEWP)—A radar echo pattern formed when a segment of a line of thunderstorms surges forward at an accelerated rate. LINE-OF-SIGHT— An     imaginary     straight     line between a radar and the target position. LLWS—Low-level wind shear. LMT—Local Mean Time. M MACROBURST—A large downburst with 4 km (2 nmi) or larger outflow size with damaging wind lasting 5 to 20 minutes. MESOCYCLONE—A region in a supercell thunderstorm  that  rotates  (usually  cyclonically) and is correlated with severe weather. METEOROLOGY— The  study  of  phenomenon  of the  atmosphere. METVANS—USMC  mobile  meteorological  vans. Highly  transportable,  completely  equipped meteorological facilities constructed as complete modules  in  cargo  containers. MF—Medium frequency. (300 kHz to 3 MHz.) MHz—Megahertz. Equal to one million hertz (10⁶). MICROBURST—A small downburst, 1 to 5 km (0.5 to 2.5 nmi) in outflow size, with peak winds lasting 2 to 15 minutes. MICROMETER— A  unit  of  length  equal  to  one millionth (10^-6) of a meter. Also called a micron. AI-3