( CNN ) -- The tornado that tore through the Oklahoma City suburbs this week ranks among the strongest storms ever to strike the United States , packing powerful winds that topped 200 mph . Officials from the National Weather Service gave the tornado that hit Moore on Monday a preliminary EF5 rating -- the highest score on the scale that measures tornado intensities . The Enhanced Fujita scale uses the physical damage caused by the storm to estimate how fast the wind was blowing . Opinion : How can we be safe from tornadoes ? Teams are still evaluating the destruction , and the rating released Tuesday is preliminary . So far , they 've found that the tornado spanned 1.3 miles -- the length of more than 22 football fields lined up end-to-end -- carving a 17-mile path of destruction . Damage assessments show that the tornado was an EF5 for at least some of the time it was ravaging the area near Oklahoma City . Oklahoma City Mayor Mick Cornett did n't mince words Tuesday when he described what he saw . `` We 're talking levels of debris that 's 4 feet high , as far as you can see . And we 're talking about cars that are upside-down and school books and children 's toys and trees without bark , '' he said . `` This was the storm of storms . '' Tornado prediction is improving , scientists say . As officials continue to assess the damage , here are CNN senior meteorologist Dave Hennen 's responses to some key questions about the storm : . What are EF5 storms ? Storms now used the Enhanced Fujita scale , or EF scale , which is based on damage , which than translates to estimated winds . EF5 storms are the strongest storms on Earth , with winds of over 200 mph . How frequent are EF5 storms ? You can go years without an EF5 tornado . In fact , since 1950 this is only the 59th tornado on record that has reached that threshold . How frequent are storms of this strength in this area ? While EF5 storms are rare , the area in the Plains known as `` Tornado Alley '' is a focus for when this happens . There also seems to be a focus for strong tornadoes in an area known as `` Dixie Alley , '' which covers parts of the Southeast and includes Mississippi , Tennessee , Alabama and Georgia . Opinion : The making of a nightmare tornado . What factors give rise to a storm of this strength ? A number of factors have to come together at the right time and place to produce a strong tornado . The clash of warm and cold air at the surface combined with lift in the atmosphere and strong winds both at the ground and high above help contribute . The greater the temperature differences and the winds , the greater the chance for supercells , or the thunderstorms that produce tornadoes . Deadliest tornadoes on record . How long does it take to assess the strength of a storm ? Why does it take so long ? After a tornado , the local National Weather Service office sends a team to take a look at the damage . In this case , the Norman , Oklahoma , office sent numerous teams in the field to evaluate damage . Since this storm path was 17 miles long and the damage path was so wide , it takes time to see all of the damage . Some people are calling this the strongest storm ever . Is that accurate ? Crews are still surveying the damage . The strongest tornado on record to date struck Moore in 1999 . It had winds recorded at 318 mph at 300 feet above the earth 's surface . At the surface , officials estimated winds were at 250 mph . The estimated winds of this week 's storm are 200-210 mph , but survey teams are still evaluating . It 's safe to say this is one of the strongest tornadoes . Moore in bull's-eye twice , science may know why . CNN 's Emanuella Grinberg contributed to this report .
Officials give the Oklahoma tornado a preliminary EF5 rating . Storm 's winds topped 200 mph as it carved a 17-mile path of destruction . Tornado spanned 1.3 miles . CNN senior meteorologist : `` It 's safe to say this is one of the strongest tornadoes ''