Alberta's Canada Day tornado given EF4 rating

A team of experts has classified a tornado that tore a path of destruction near Carstairs, Alta., on Canada Day an EF4.

A team of experts has classified a tornado that tore a path of destruction near Carstairs, Alta., on Canada Day an EF4.

The Northern Tornadoes Project (NTP), in collaboration with Environment and Climate Change Canada's (ECCC) Prairie and Arctic Storm Prediction Centre, made the determination Tuesday following an analysis of the damage left behind.

"The survey teams found that there was enough evidence to rate the tornado damage at EF4, with a maximum wind speed of 275 km/h," NTP said in a statement.

"The preliminary path length is 15.3 kilometres and maximum path width 620 metres."

Officials say 12 homes were impacted by the storm: three were destroyed, four were left uninhabitable and five others were damaged.

According to ECC, the EF (Enhanced Fujita) Scale is a six-point scale that ranges from zero (weakest) to five (strongest). It was adopted in April 2013 as "a more modern and improved version of the original Fujita Scale or F Scale.

"Environment Canada used the F-Scale to rate wind damage, in particular tornado damage, for several decades. However, the F-Scale, developed by Prof. T. Fujita in the 1960s, was found to have significant shortcomings. There was a limited number of damage indicators with which to rate damage, and engineering studies had shown that the F-Scale wind speeds were not well correlated with actual damage," ECCC said.