2-mile wide Mississippi tornado, state’s largest on record, carved a 67-mile path

One of the two tornadoes that terrorized southeastern Mississippi on Sunday has been confirmed as the state’s widest tornado on record. The EF4 vortex with winds topping 170 mph was as wide as two miles as it carved a 67-mile path.

The tornado, which was on the ground for an hour and 17 minutes as it plowed down vegetation and demolished structures between Mississippi's Jefferson Davis and Clarke counties, caused EF4 damage in the community of Moss. The majority of damage elsewhere was found to be in the EF2 to EF3 range, commensurate with winds between 111 and 165 mph.

The violent tornado occurred during a two-day outbreak in which at least 78 tornadoes touched down in 10 states, resulting in at least 34 fatalities.

Sunday's was so destructive that its scar on the land surface was visible from space.

Tornadoes are rated on the 0 to 5 Enhanced Fujita (EF) scale based on the degree of damage they cause and their estimated peak winds. Before February 1, 2007, tornadoes were rated on the 0 to 5 Fujita (F) scale, which assigned higher wind speeds to some damage indicators than meteorologists and engineers say may have been realistic.

A monster

The preliminary EF4 rating given to Sunday's tornado was assigned based on estimated 178 mph winds that swiped a neighborhood virtually bare.

"Several homes on the road [in Moss] were reduced to rubble and hard to distinguish. One home had a closet left standing," wrote the National Weather Service in Jackson in its survey notes. The nearby First Baptist Church was also destroyed.

The wedge tornado's rare width of "at least 2 miles" according to the National Weather Service in Jackson, Mississippi.

It was Mississippi's widest tornado on record, the NWS office in Jackson confirmed, replacing a 1.75-mile-wide tornado that tracked 149 miles across Mississippi and Louisiana in 2012. That tornado, which killed 10, was also an EF4.

Sunday's EF4 tornado was accompanied by a mile-wide EF3 tornado that paralleled its predecessor to the north, tracking 82.5 miles along a path beginning in Lawrence County.

An elite tier of tornadoes

Mile-wide tornadoes are rare, with two-mile-wide tornadoes only occurring perhaps every few years.

The May 31, 2013, tornado in El Reno, Oklahoma - which was rated an EF3 despite radar-estimated winds nearing 300 mph - is listed as the nation's largest tornado. It swelled to 2.6 miles in diameter as it crossed Oklahoma Highway 81, killing nine people - including four storm chasers.

That El Reno tornado's rating was likely a severe underestimate of the its true force, but tornado ratings can only be assigned based on observed damage. In rural areas, it can be challenging to find evidence of the highest-end winds, precluding an EF5 rating.

That may come into play in Mississippi, where relatively few structures were impacted considering the tornado's ultra-long path. Meteorologists can only use tree damage to estimates winds up to 167 mph in the most extreme cases - shy of the 200 mph winds that would necessitate an EF5 rating.

For that category, well-constructed structures would generally need to be hit by the tornado's narrow strips of extreme winds.

Notable giant tornadoes

Other tornadoes have approached or exceeded two miles in width before, including a 2.5-mile-wide F4 tornado that struck Hallam, Nebraska, on May 22, 2004. At the time, it was considered the largest tornado on record.

There is some speculation about a tornado that occurred near Edmonson, Texas, on May 31, 1968. Tornado historian Thomas Grazulis said "the huge rotating mass of cloud was up to three miles in width," but he lists the core of tornadic winds as being closer to 1.7 miles wide.

In particularly humid environments, the rotating part of the thunderstorm - known as the mesocyclone - can condense into a cloud that scrapes the ground surrounding the twister. Meanwhile, powerful winds rushing into the strongest tornado can exceed 100 mph. That often makes finding the "edge" of a tornado difficult.

A sneaky width winner in 1999?

There's also an often-overlooked tornado that struck Mulhall, Oklahoma, on May 3, 1999. It occurred during Oklahoma's most prolific tornado outbreak on record, when 63 tornadoes - many large and destructive - swirled across the Sooner State. The date is most often remembered for the F5 tornado that devastated much of Moore, which was struck by another EF5 in 2013.

One supercell thunderstorm, labeled "storm B," produced 20 tornadoes in 5 hours, including the Mulhall tornado. That tornado was rated an F4, and destroyed about two thirds of the roughly 130 homes in town as well as a water tower and an elementary school.

Doppler radar estimates of the Mulhall tornado suggest that the tornado-force winds associated with it may have spanned more than four miles wide. A team of tornado research scientists concluded that "wind speeds capable of causing significant damage, [greater than 96 mph], extended across a swath over [4.3 miles wide]."

They wrote that the contour of extreme winds associated with the Mulhall tornado was "substantially wider than the damage swath of the Hallam, Nebraska, tornado of 22 May 2004."

The region could be in for more severe weather next week.