DURHAM, N.H. - Mary Stampone, assistant professor of geography at the University of New Hampshire and the New Hampshire State Climatologist, is available to discuss tornado activity in the state, including the annual frequency of tornadoes and periods of previous high tornado activity.

The National Weather Service is investigating whether a tornado touched down in Gorham, Sunday, June 6, 2010.

According to Stampone, New Hampshire can expect an average of one to two tornadoes a season. "They are more common in the southern counties and tend to peak in July. They are typically between EF0-EF3 in intensity on the Enhanced Fujita Scale," she says. 

The Enhanced Fujita Scale measures tornadoes on a scale of EF0 to EF5.

The state experienced a period of high tornado activity from the early 1960s to early 1970s, Stampone says. In 1963, nine tornadoes were reported in the state, and seven in 1972. In many of the years during that period, the state recorded three to four tornadoes a year. However, the state has not experienced anything like that since.

According to the New Hampshire Department of Safety, the worst tornado in New Hampshire history occurred July 24, 2008, when a large thunderstorm system spawned a tornado that touched down in Epsom and Northwood just before noon. This EF2 tornado, with winds up to 157 mph, tore through the middle of the state, and headed northeast to Ossipee. It killed one person, destroyed or damaged 60 structures and damaged thousands of acres of forest. It resulted in a Presidential Disaster Declaration for the affected counties.

Most tornadoes occur between 3 and 9 p.m. and have an average forward speed of about 30 mph, according to the National Weather Service. For the 40-year period between 1950 and 1990, 74 tornadoes occurred in Maine while 68 tornadoes occurred in New Hampshire. During this period, the average path length of the tornadoes was 1.08 miles for Maine and 1.64 miles for New Hampshire. 

The New Hampshire State Climate Office resides within the Department of Geography at the University of New Hampshire. The University of New Hampshire, founded in 1866, is a world-class public research university with the feel of a New England liberal arts college. A land, sea, and space-grant university, UNH is the state's flagship public institution, enrolling more than 12,200 undergraduate and 2,200 graduate students.

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