Understanding Tornado Watches
A tornado watch is issued when meteorologists determine that weather conditions are right for tornadoes to develop. This means the atmosphere has the necessary ingredients: warm, moist air near the ground, dry air aloft, and strong wind shear. Watches are preventive measures that tell people to stay alert and prepared. During a watch, people should monitor weather reports and know where they will take shelter if a warning is issued.
Understanding Tornado Warnings
A tornado warning is issued when a tornado has been spotted by trained spotters or indicated by weather radar, meaning danger is immediate. Warnings are more urgent than watches and require people to take action immediately by moving to a safe shelter. Meteorologists use Doppler radar to detect the rotation of storm clouds that indicates a tornado is forming or already exists.
Geographic and Time Differences
Tornado watches cover a wide area, sometimes spanning multiple counties across one or more states, and usually last between 4 to 8 hours. Tornado warnings cover a much smaller, specific area where danger is immediate and typically last from a few minutes to about an hour. The smaller warning area allows meteorologists to focus on the exact location where a tornado threatens.
Who Issues Watches and Warnings
The National Oceanic and Atmospheric Administration's Storm Prediction Center issues tornado watches for large regions based on weather models and atmospheric data. Local National Weather Service offices issue tornado warnings for their specific areas using radar data, trained spotter reports, and local weather information. This two-level system ensures people receive both advance preparation information and immediate danger alerts.
How to Respond
When a tornado watch is issued, people should stay informed through weather alerts, review their shelter plan, and keep emergency supplies accessible. When a tornado warning is issued, people must take immediate action by moving to an interior room on the lowest floor of a sturdy building, away from windows. The key difference is that watches call for awareness and preparation, while warnings call for immediate protective action. 
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