A Tornado Emergency is the highest level of Tornado Warning the National Weather Service (NWS) issues. Forecasters reserve it for very rare cases when a tornado poses a severe threat to human life and catastrophic damage is imminent or already happening, and its headline names the places at risk.
How it fits the warning tags
Tornado Warnings carry a damage threat tag with three levels. The base level, with no tag, is the default. CONSIDERABLE marks a strong, ongoing tornado and carries Particularly Dangerous Situation wording, and CATASTROPHIC is the Tornado Emergency.
The national warning directive lets a local office invoke the CATASTROPHIC level with concurrence of the on-duty shift leader or supervisor. The warning then adds the headline TORNADO EMERGENCY FOR followed by the affected locations.
What has to be true
Choosing CATASTROPHIC sets the source tag to TORNADO…OBSERVED and lists the hazard as a deadly tornado. NWS describes the situation as a violent tornado, capable of catastrophic damage and a severe threat to human life, that is already ongoing.
An observed tornado is one confirmed by reliable reports or by radar evidence such as debris. Rotation on radar alone does not meet that bar.
Where it came from
The NWS office in Norman, Oklahoma, issued the first Tornado Emergency for the Oklahoma City metro area on the evening of 05/03/99. The office wrote that the wording was meant to get attention and show the event was different from normal.
The headline is now part of the formal warning structure. It parallels the Flash Flood Emergency at the top of the flash flood warning scale.
What it does not tell you
Every Tornado Warning already triggers Wireless Emergency Alerts (WEA) on phones, so the alert alone does not show that a warning has reached emergency level. Read the headline and tags.
The headline names communities, not an exact damage path, and its absence does not mean a tornado is weak. A base or CONSIDERABLE warning can still involve a deadly tornado.