Answer to Question 1
ANSWER: Sometimes a large, well-organized frontal system will spawn multiple supercells, each producing its own family of tornadoes. When a large number of tornadoes develop in association with a particular weather system (typically six tornadoes or more, although there is no strict definition), it is referred to as a tornado outbreak. An outbreak may extend over multiple days, as long as no more than a few hours (typically six) elapse without at least one tornado being observed in the outbreak region.
Answer to Question 2
ANSWER: The Fujita scale classifies tornadoes according to their rotational wind speed. The tornado winds are estimated based on the damage caused by the storm. The Enhanced Fujita Scale, or simply the EF Scale, attempts to provide a wide range of criteria in estimating a tornados winds by using a set of 28 damage indicators, including small barns, mobile homes, schools, and trees. The quality of building construction is also taken into account. Each structure or object is examined for the degree of damage it sustained. The combination of the damage indicators along with the degree of damage provides a range of probable wind speeds and an EF rating for the tornado.