( CNN ) -- Storms tore a deadly path through at least three counties in Arkansas on Sunday evening and ripped houses , cars and forests to shreds , strewing rubble for miles . Though it 's not yet official , weather forecasters strongly suspect tornadoes are to blame for at least 14 deaths and devastating damage in the state . Two more people died in storms on Iowa and Oklahoma . A tornado 's shearing , twisting winds can exceed 300 mph , and though they usually last only seconds , some cyclones endure much longer , razing swaths up to a mile wide that scar landscapes for months to come and inflict tragic human losses . The United States has the highest number of tornado occurrences in the world , with an average of 1,200 tornadoes reported each year , according to the National Weather Service . Arkansas winds 'severe ' Meteorologists rank a tornado based on the strength of its winds and the area over which it spreads destruction . The Enhanced Fujita Scale assigns tornadoes corresponding numbers from EF0 , with gusts from 65 to 85 mph , to the mightiest EF5 , with gusts over 200 mph . The EF0 's winds are described as `` gale '' winds ; those of the EF5 are called `` incredible . '' The figures for tornadoes ' wind speeds are based on assessments of the damage they leave behind on the ground . Only 59 EF5 storms have hit the United States since 1950 , according to weather service records . The latest one devastated Moore , Oklahoma , in May of last year . Though meteorologists have not finished analyzing the most recent Arkansas storm , so far the state has been spared an EF5 , the NWS says . CNN meteorologist Chad Myers estimates that the winds that ravaged the town of Mayflower , Arkansas , on Sunday had speeds of 130 to 150 mph , which would correspond to an EF3 tornado , which the Fujita Scale describes as `` severe . '' Let 's take a look at the nature of the strongest tornadoes , the EF5s , the strongest storms on Earth . Where do storms of this strength most commonly hit ? While EF5 storms are rare , the area in the Great Plains known as `` Tornado Alley '' gets more than its share . The alley runs through Texas , Oklahoma , Kansas and Iowa . 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 . 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 , the thunderstorms that produce tornadoes . 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 the case of the monster twister in Moore last year , the Norman , Oklahoma , office sent numerous teams into the field to evaluate damage . Since this storm path was 17 miles long and the damage path was so wide , it took time to see all of 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 . Officials estimated winds at the surface were at 250 mph . Read more about tornadoes .
It 's not yet official , but forecasters suspect tornadoes caused 16 deaths Sunday . The United States has the highest number of tornadoes in the world -- 1,200 per year . Comment: