What are the Positive effect on the tornado of May 3 1999 Oklahoma?

The main positive effect of the May 3, 1999 F5 tornado was a new type of unofficial weather advisory: the tornado emergency. A tornado emergency is more urgent than an ordinary tornado warning. It means that a large and potentially very destructive tornado is threatening a populated area. One case of a tornado emergency's effectiveness was on May 4, 2007 when an EF5 tornado destroyed 95% of Greensburg, Kansas. Despite this the death toll was limited to 11. Countless more lives had been saved.