An approximation to the dynamical equations of motion whereby density is assumed to be constant except in the buoyancy term of the vertical velocity equation.
A set of different forecasts all valid at the same forecast time(s).
An imaginary volume of fluid to which may be assigned various thermodynamic and kinematic quantities.
A simulation approach to studying the chemical evolution of a (natural) system.
A forecast of weather conditions for a period extending beyond three or more days from the day of issuance.