Tornado Watch / Tornado Warning / Tornado Emergency

IT'S TIME TO INTRODUCE PRECAUTION MEASURES AND WARNINGS AGAINST ENVIRONMENTAL DISRUPTIONS IN PORTUGAL

A tornado watch (SAME code: TOA, sometimes referred to as a red box by meteorologists and storm chasers) is issued when conditions are right for a tornado to form. Since any thunderstorm capable of producing a tornado is defined as severe, a tornado watch is also automatically a severe thunderstorm watch. In most cases, the potential exists for large hail and/or damaging winds in addition to the tornadoes.
A tornado watch means that the conditions have created a significant risk of a tornado occurring.

A tornado warning (SAME code: TOR) is an alert issued by weather services to warn that severe thunderstorms with tornadoes may be imminent. It can be issued after a tornado or funnel cloud has been spotted by eye, or more commonly if there are radar indications of tornado formation. When this happens, the tornado sirens may sound in that area, letting people know that a tornado was seen or is forming nearby. Issuance of a tornado warning indicates that residents should take immediate safety precautions.

A Tornado Emergency is enhanced wording of tornado warnings used by the National Weather Service (NWS) in the United States during significant tornado occurrences in highly populated areas. Although not a new warning type from the NWS, instead issued in a Severe Weather Statement (or in rare cases, in the initial Tornado Warning), a Tornado Emergency generally means that significant, widespread damage is expected to continue and a high likelihood of numerous fatalities is expected with a large, strong to violent tornado.

^{in Wikipedia}