What enhanced warning phrase was first used during the May 3, 1999 Oklahoma tornado outbreak?

The enhanced warning phrase first used during the May 3, 1999, Oklahoma tornado outbreak was “tornado emergency.”

The phrase was introduced as a special National Weather Service statement when an exceptionally large and destructive tornado approached the Oklahoma City metropolitan area. Forecasters in Norman, Oklahoma, were tracking the storm as it moved from Bridge Creek and Moore toward Oklahoma City, Del City, and Midwest City.

The first tornado emergency was issued at 6:57 p.m. Central Daylight Time. Unlike an ordinary tornado warning, the statement emphasized that a large tornado was confirmed or strongly indicated and that people in the threatened area faced an extreme, immediate danger. It was initially issued as a standalone severe-weather statement rather than simply replacing the original warning.

The phrase is often confused with “particularly dangerous situation,” or PDS, which is used for some severe-weather watches and warnings. A tornado emergency is not a separate tornado intensity rating; it is an urgent warning phrase used when forecasters believe a violent tornado is threatening a populated area. The 1999 Bridge Creek–Moore tornado ultimately killed 36 people directly.