1821 Sullivan–Merrimack County tornado

On the evening of September 9, 1821, a tornado hit the towns of Cornish and Croydon, New Hampshire, in the United States. This tornado is known as the 1821 Sullivan–Merrimack County tornado, the more deadly and longer track tornado out of the two F4 tornadoes during the September 1821 New England tornado outbreak.

Meteorological synopsis

The afternoon of September 9, 1821, brought intense heat and humidity to New England. Heavy southwestern winds fed this warm air mass, generating massive convective instability across the region.

The atmospheric balance broke around 5:00 PM when a fast cold front slammed in from the northwest. This boundary triggered a rapid line of severe thunderstorms. A sharp wind shift toward the north suddenly accelerated local wind shear, causing the storm cells to rotate into organized supercells.

Local diaries and records note the primary funnel came down late that afternoon. While modern digital climate databases code the touchdown time as a baseline 12:45 AM (0045) value, local tracking verifies the late afternoon arrival. Based on the physical scars left in the terrain, modern meteorologists rate the track as an F4 or EF4 equivalent tornado, with core winds peaking around .

People who watched the storm described a complex multi-vortex structure, seeing distinct smaller sub-vortices spinning rapidly inside the main parent column. The intense pressure drop inside the core generated massive suction; it briefly dropped a local pond's water level in Warner by three feet and pulled sheets of water straight up out of Lake Sunapee into the sky.

Tornado summary

The violent F4 tornado carved a highly destructive path across New Hampshire. Its damage track extended greater than up to an estimated across Sullivan County and Merrimack County. At its peak intensity, the funnel expanded to a maximum width of . The storm remains recorded as the deadliest tornado in New Hampshire history, causing six confirmed deaths and wounding hundreds of residents.

The localized sequence of impact progressed sequentially through the following communities. Cornish and Croydon (Sullivan County): The tornado initiated heavy damage here, leveling entire forests and scouring several farm buildings directly down to the ground. Sunapee: Moving southeast, the storm tore apart residential structures, carrying heavy household furniture a distance of entirely across Lake Sunapee. New London (Merrimack County): The funnel grew to its maximum width, devastating multiple homes, destroying 80 agricultural orchards, and obliterating a major millyard. The updraft hurled 30,000 board feet of structural timber up to away into the town of Canterbury. Sutton and Warner: The tornado maintained violent intensity as it moved past Mount Kearsarge. It struck the small settlement of Kearsarge Gore near Warner, completely fracturing and dismantling all seven homes in the village into splinters. The tornado eventually entered Boscawen, where the funnel finally lifted and dissipated.

See also

• September 1821 New England tornado outbreak
• List of North American tornadoes and tornado outbreaks