Forecast
An estimate of future atmospheric conditions; read it with its issue date and forecast horizon.
Hours or daysWeather and earthquake glossary
A short guide to layers, units and the differences between observations, forecasts and visualizations.
Model run
A model calculation cycle initialized with a set of starting conditions.
UTC date and timeEnsemble
A set of simulations used to explore forecast scenarios and spread.
Members and probabilitiesGust
A brief increase in wind speed relative to sustained conditions.
km/h, m/s or ktFeels like temperature
An index approximating perceived temperature using the variables in its formula.
°C or °FRelative humidity
The ratio of present water vapor to saturation at the same temperature.
%Accumulated precipitation
Water that falls or is forecast to fall over a defined interval.
mmReflectivity
A measure of radar echo strength; it describes hydrometeors and does not directly equal surface rainfall.
dBZBrightness temperature
Equivalent temperature derived from radiation measured by an infrared sensor.
K or °CCloud top
The upper boundary of a cloud; its height may be estimated from thermal information.
km or mTropical cyclone
An organized low pressure system with convection and circulation in tropical regions.
Wind and pressureCold front
A boundary where a cold air mass advances into warmer air.
Position and movementITCZ
The Intertropical Convergence Zone: a shifting belt where winds meet and convection is often favored.
CoordinatesMonsoon trough
An elongated low pressure axis associated with tropical monsoon circulation.
CoordinatesTropical wave
A disturbance in tropical flow represented by an axis; it does not by itself imply hurricane formation.
Coordinates and movementENSO
Coupled ocean and atmospheric variability in the tropical Pacific, including El Niño and La Niña.
Indices and anomaliesSea temperature anomaly
The difference between sea surface temperature and its climate reference.
°CAtmospheric pressure
Force per unit area exerted by the atmosphere.
hPaEarthquake magnitude
A measure of an earthquake's size, distinct from shaking intensity at each location.
Magnitude scaleEarthquake intensity
The degree of effects or shaking at a location; an estimate is not a field observation.
Intensity scale