The tornado, which was on the ground for 1 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. High-end EF4 damage was also discovered Thursday afternoon near Bassfield, evidence of winds up to 190 mph. The majority of damage elsewhere was found to be in the EF2 to EF3 range, commensurate with winds between 111 and 165 mph.
Sunday’s twister was so destructive, 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 Feb. 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 felt may have been realistic.
Mississippi’s widest tornado was a monster
On Thursday, meteorologists from the National Weather Service in Jackson, Miss. dispatched to the scene found evidence of winds up to 190 mph near the town of Bassfield.
“I can tell you generally that the area where that came from was east of Bassfield, kind of from the Graves Keys Road area up towards the Jefferson Davis County line," said Daniele Lamb, a meteorologist at the Jackson office.
"We haven’t really finished organizing all the details and everything. We’ve been having calls with outside experts. We’ve also been going over satellite data and other things coming in.”
Lamb said the survey has been unusually arduous given the extreme nature of the event.
“We’re used to dealing with a lot of tornadoes,” said Lamb. “But these were so rare because not only are they really wide, but these are wide along such a long swath.”
Previously, a preliminary EF4 rating had been awarded to Sunday’s tornado based on estimated 178 mph winds that wiped a neighborhood virtually bare in the town of Moss.
“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 their initial survey notes.
The nearby First Baptist Church was also destroyed, pointing to winds as high as 175 mph.
Even more remarkable than the violent EF4 winds was the wedge tornado’s enormous width of 2.25 miles as reported by the National Weather Service. That puts the twister into an elite group of extreme wedge tornadoes.
In fact, it’s the nation’s third-widest tornado on record — behind only the 2013 El Reno, Oklahoma tornado (2.6 miles wide), and the 2004 Hallam, Nebraska tornado (2.5 miles wide).
It also claims the top spot as Mississippi’s widest tornado on record, the Weather Service office in Jackson confirmed, beating out a 1.75-mile-wide tornado that tracked 149 miles across Mississippi and Louisiana in 2010. Yazoo City, Miss., suffered major damage. That tornado, which killed 10, was also an EF4.
Sunday’s tornado was accompanied by a mile-wide EF3 monster that paralleled its predecessor to the north, tracking 82.5 miles along a path beginning in Lawrence County. That tornado was found to be up to 1.16 miles wide.
An elite tier of tornadoes
The enormous twister raises the question for some as to how large tornadoes can get. Mile-wide tornadoes are rare, with two-mile-wide tornadoes only occurring perhaps every few years.
The May 31, 2013, tornado in El Reno, Okla. — which was rated an EF3 despite radar-estimated winds nearing 300 mph — is listed in the books as the nation’s largest tornado. It swelled to 2.6 miles in diameter as it crossed Oklahoma Highway 81, killing nine — including four storm chasers.
The El Reno tornado’s rating was probably a severe underestimation of 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 have come into play in Mississippi, where relatively few structures were impacted considering the tornado’s ultralong path. Meteorologists can only use tree damage to estimate winds up to 167 mph in the most extreme cases — shy of the 200 mph winds that would necessitate an EF5 rating.
Meteorologists did note at least half a dozen instances of EF4 tree damage, rating each case as high as possible on the tree damage indicator scale.
For the EF5 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 that struck Hallam, Neb., on May 22, 2004. At the time, it was considered the largest tornado on record.
There is speculation about a tornado that occurred near Edmonson, Tex., on May 31, 1968. Tornado historian Thomas Grazulis states that “the huge rotating mass of cloud was up to three miles in width,” but 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 inflow winds rushing into the strongest tornado can exceed 90 or even 100 mph. That often makes finding the “edge” of a tornado a not-so-easy task.
A sneaky width winner in 1999?
There’s also an often-overlooked tornado that struck Mulhall, Okla., 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 decimated much of Moore, which was struck by another EF5 in 2013.
One supercell thunderstorm, labeled “storm B,” produced 20 tornadoes in five hours, including the Mulhall tornado. That tornado was rated an F4, and destroyed about two-thirds of the roughly 130 homes in town. A water tower and elementary school also succumbed to the tornado.
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.”
Regardless of which tornado holds the record, what happened in Mississippi on Sunday is remarkably impressive. As communities continue to pick up the pieces, it must be remembered that tornado season is still in full force — with more potential severe weather next week.