National Weather Service: Rare tornado strikes in New Hampshire, knocks over 1,000 trees

A rare EF1 tornado with maximum wind speeds of 90 mph traveled between two New Hampshire towns bordering Vermont on Monday, National Weather Service meteorologists said.

Reaching 330 yards at its largest size, the weak tornado traveled 4.8 miles during the approximately six minutes it was on the ground, according to NWS Warning Coordination Meteorologist Donald Dumont.

He said it moved from the 4,800-population town of North Charlestown to the neighboring city of Claremont between 6:22 p.m. and 6:28 p.m.

The NWS verified that a dash camera video taken by a man driving a vehicle in Claremont accurately depicted the tornado that passed through the area, Dumont told USA TODAY. 

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The tornado left behind no significant structural damage, though the NWS reported a few homes suffered minor damage from the approximately 1,000 trees its winds knocked over, according to Dumont.

The NWS office in Gray, Maine, monitored a line of thunderstorms Monday night and issued a thunderstorm watch – and then a severe thunderstorm warning – for the area, Dumont said. 

“There was a pretty decent line of storms coming through,” he said, adding that all of New Hampshire experienced heightened thunderstorm activity that evening. “It was unseasonably warm and humid for early May," he said.

New Hampshire doesn’t see many tornado strikes, said AccuWeather senior meteorologist Paul Walker.

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Between 1951 to 2020, Walker’s period of record showed only 107 tornadoes that have touched down in the New England state, with some years of no confirmed tornadic activity. Twisters are rare enough that there are no tornado sirens in the Granite State, Dumont said. 

Tornadoes are usually observed during June and July, Walker said. The few that do occur are normally not as powerful and destructive as the tornadoes synonymous with Tornado Alley in the Midwest, Walker said. 

“There have been some reports of EF3 tornadoes in New Hampshire, but they're often the reports of EF2 and lower,” he said.

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Typically, a strong cold front traveling through the northern end of a squall line could create a recipe for tornadic activity in New Hampshire, with most tornado reports coming from the central and southern parts of the state, Walker said.

“You also have the tropical features that move up into the area, and you can get these tornadoes whenever a tropical feature moves up into New England from those storms,” he said. 

Tornadoes across New England as a whole are rare, and they normally spend less time on the ground than tornadoes formed from supercells that most people may be used to hearing about, Dumont said.

Tornadoes like the one observed Monday in New Hampshire are called quasi-linear convective system, or QLCS, tornadoes, he said. 

“How they form is a little bit different, that's why they're weaker, and they don't last as long, they’re usually on the ground for five minutes,” Dumont said.

They occur quickly, making them much tricker to predict compared to supercell tornadoes. They're more difficult to issue a tornado warning for and are harder to recognize on a radar in a timely manner, he added. 

“(With) supercells, you can typically see the rotation in the storm for lot longer periods of time,” he explained.