North Dakota Tornado Was Nation's Strongest in 12 Years

A deadly tornado that tore across southeastern North Dakota this summer has been upgraded to an EF5 with winds topping 200mph, the strongest classification of tornado and the first on American soil in 12 years, meteorologists said Monday. The June 20 twister in Enderlin caused significant damage and killed three people. At its largest, the tornado was 1.05 miles wide and carved a path across the prairie for just over 12 miles, the AP reports.

• Meteorologists from the National Weather Service office in Grand Forks estimated the tornado's winds reached 210mph, according to the newly released analysis. The 1999 Bridge Creek-Moore tornado in Oklahoma holds the record of the strongest winds ever recorded at 321mph.

• Since the National Weather Service began using the Enhanced Fujita scale in 2007, there have been 10 tornadoes categorized as EF5. The last one was in Oklahoma in 2013. Researchers say the EF5 "drought" is due to changes in surveying practices, not natural causes, the Bismarck Tribune reports.
• "In the last kind of 12 years, there's been several strong tornadoes that have come close, but there haven't been known damage indicators at that time to support the EF5 rating," says Melinda Beerends, meteorologist in charge at the National Weather Service in Grand Forks. "It's hard sometimes to get tornadoes to hit something."
• The twister destroyed farmsteads, tipped over fully loaded rail cars, toppled transmission towers and uprooted trees. One tanker car was hurled far from the rest. One farmstead had its foundation swept clean, with just the basement remaining and debris scattered downwind. Two men and a woman were killed at two locations near Enderlin, about 40 miles southwest of Fargo.

• Meteorologists from the Grand Forks office headed into the field the next morning to assess the damage. Determining a tornado's strength usually takes days or weeks, as meteorologists study the damage to buildings and trees. This case took much longer because of the unusual damage to rail cars. The initial estimate for the tornado in the days afterward was an EF3.
• "Further analysis of the trees surrounding the Maple River show extensive tree damage throughout the entire river valley with only stubs of large branches or large trunks remaining and debarking with a 'sandpapering' effect prevalent," the NWS said in its report. "Trees with attached root ball displacements were noted, including one where the original location could not be determined."
• The tornado, the first EF5 to hit North Dakota since 1957, was one of 80 known tornadoes in the state over the summer, breaking the record of 61 set in 1999, the Tribune reports.