Knowra Severe weather warning Severe weather warning An official alert that hazardous weather is occurring or expected in a defined area. It communicates an immediate threat so people can take protective action.
Weather radar : A remote-sensing system that detects precipitation and estimates its movement and intensity. Radar can reveal storms capable of producing hazards before they reach communities.
Severe thunderstorm : A thunderstorm meeting defined criteria for hazards such as damaging winds, large hail, or tornadoes. Severe thunderstorms are a common subject of dedicated warnings.
Protective action : A measure taken to reduce harm from an imminent or ongoing hazard. Warnings are issued to prompt actions such as sheltering or evacuation.
Tornado outbreak of 1974 : A major United States tornado outbreak on April 3–4, 1974, that produced 148 tornadoes across several states. The outbreak exposed challenges in forecasting and communicating simultaneous tornado threats.
Doppler effect : The change in a wave’s observed frequency when its source and observer move relative to each other. Doppler radar uses frequency shifts to estimate winds inside storms.
Tornado warning : An official alert that a tornado has been sighted or indicated by radar in a specified area. It is a specific warning for a rapidly dangerous severe-weather hazard.
Severe weather shelter : A place designed or selected to protect people from hazards such as tornadoes, wind, or flying debris. A warning can trigger movement to the safest available shelter.
Tri-State Tornado : A violent tornado on March 18, 1925, that devastated parts of Missouri, Illinois, and Indiana. Its catastrophic impact helped spur stronger organized storm observation and warning efforts.
Numerical weather prediction : Computer simulation of the atmosphere using physical equations, observations, and initial conditions. Forecast models help identify developing hazards and estimate where they may travel.
Flash flood warning : An alert that rapid flooding is occurring or imminent in a specified area. Flash flooding shows that warnings cover hazards beyond storms and wind.
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