Doppler Radar Helped to Warn Town of Tornado

Doppler Radar Helped to Warn Town of Tornado - An F3 tornado. Winds roaring at 280 km/h. And just 12 minutes for Goderich residents to find shelter.

The weather pattern that turned Ontario's prettiest town into a field of debris developed in a flash over Lake Huron with a pattern meteorologists quickly recognized as tornado trouble.

But if the same storm had hit 10 years ago, before Doppler radar was installed at the Exeter weather station, Goderich might not have received any warning at all, says an Environment Canada meteorologist.

"It's definitely a possibility," said John Paul Cragg. "You wouldn't have the same level of certainty we have today."

Doppler radar allows meteorologists to see two classic indicators of a possible tornado: The c-hook echo that picks up the movement of moisture (rain and hail, or even debris) within a storm cell; and a circular pattern to the air movement, also caused by moisture.

Sunday, both signatures showed up on radar, Cragg said, adding the system worked as it should, although the further from the shoreline and the radar station in Exeter, the less specific or reliable the detail becomes.

"Sometimes, when these storms come, it's a lot more obvious than other times," said Cragg.

"The storm passed across Lake Huron, so we were able to rely only on (Doppler) radar and there would be no one on the ground to observe and report conditions, other than boaters."

Meteorologists from Env i ronment Canada issued a severe weather alert shortly after 2 p.m., indicating the storm could deliver heavy rain, hail and damaging winds, including the possibility of a tornado.

Then, when a twister signed its predictive signature on Doppler radar, Environment Canada issued a tornado warning at 3:48 p.m. The tornado hit at 4 p.m.

The tornado -- categorized Tuesday as F3 and packing winds strong enough to topple brick buildings -- devastated the town's historic core.

Randy Mawson, a storm investigator for Environment Canada, confirmed the tornado was an F3 with a "significant" funnel 500 metres wide that cut a swath through the town along West St. to the town square, blowing off roofs, knocking down brick walls, tossing cars and pulling down large trees.

It's the first F3 to hit the province since April 20, 1995, when two F3 tornados touched down in Grey, Wellington and Dufferin counties and injured nine people.

The federal government spent $35 million in the late 1990s and early 2000s to rebuild the radar network in the country and installed Doppler radar systems across Canada, specifically to provide early storm warnings.

The Exeter radar station, located northwest of London 25 km east of Lake Huron, with a range of 250 km, was upgraded in April 2000.

Mawson said Sunday's tornado weakened as it moved inland for about 20 km to Benmiller, skipping a bit along the way.