New model could provide tornado forecasts months in advance

A new model for predicting tornado activity could allow experts to prepare forecasts months or even seasons in advance, scientists say.
"The aim is to predict ahead to the following year or subsequent years about whether we'll get above or below average tornado activity in a given area," said Vincent Cheng, a postdoctoral fellow in University of Toronto Scarborough (UTSC) Ecological Modelling Lab.
The model, developed by Cheng, George Arhonditsis and Bill Gough in UTSC's Climate Lab along with colleagues at Environment Canada, uses large-scale atmospheric variables like those used by weather forecasters.
But instead of looking to predict a tornado on any specific day, it looks at variations in monthly and seasonal tornado activity relative to changes in atmospheric conditions over the same period.

Cheng said the model predicts how different conditions in the atmosphere during a thunderstorm will affect the risk of there being a tornado.
The key variables the model relies on includes the instability of the atmosphere and the change in wind speed and wind direction at different heights.

Cheng's model also takes into account the lack of accurate records in tracking tornadoes.
Tornado reports rely solely on eyewitness observations, which means they are better monitored in more populated areas.
The model bypasses that by showing the strong relationship between atmospheric variables and actual tornado occurrences.
"From observations there are only about 60 reported tornadoes in Canada per year, but that number is more like 150," said Cheng.

"When we apply the model to areas where the monitoring network is lacking we find the greatest difference is in the Northern Great Plains and the Canadian Prairies," Cheng said.
While much remains unknown about how tornadoes actually form, when one does it produces a narrow, violently rotating channel of air that runs from the base of a thunderstorm to the ground.
They are one of nature's most hazardous weather events, capable of causing significant destruction and devastation including severe injuries or death.
The goal is to be able to predict whether there will be above or below average tornado activity in a given area over a given time, said Cheng.

This information can play an important role in disaster planning or determining how tornado-resistant buildings need to be in a given area.
The study was published in the journal Nature Communications.