May 31, 1985 outbreak: How a 'lost' 14th tornado was found

Tuesday, May 31, 2016, 12:06 PM - On the final day of May 1985, a destructive and deadly swarm of tornadoes swept through southern Ontario, however for years, one of these twisters was lost from the public record. Here's how it was found.

Tuesday, May 31, 2016 marks the 31st anniversary of Southern Ontario's Black Friday, when a devastating tornado outbreak damaged thousands of buildings, caused hundreds of injuries, and claimed the lives of a dozen people before it was over.

In the aftermath of the outbreak, a total of 13 confirmed tornadoes went into the official record of the day:

• an F1 that touched down near Essa, west of Barrie, at 4:57 p.m.
• eight different F2 tornadoes, in Hopeness, Hopeville, Lisle, Wagner Lake, Reaboro, Ida, Rice Lake and Minto, scattered between 3 p.m. and 6:35 p.m.
• two F3 tornadoes, in Alma at 4:15 p.m. and Corbetton at 4:17 p.m.
• two F4 tornadoes, one starting in Grand Valley at 4:15 p.m., and tracking over 115 km to Tottenham (the longest tornado track in Canadian weather history), and one that touched down in Barrie at 5 p.m., cutting a swath through the city that damaged or destroyed up to 300 homes, and resulted in 155 injuries and 8 dead.

According to Geoff Coulson, Environment Canada's Warning Preparedness Meteorologist, there were other strong storms that swept through the area on that day. At the time, however, no other tornado reports made it into the official record.

Credit: Animation by S. Sutherland, from slides provided by Environment Canada

As revealed in the animation above, though, there was actually one more - a "lost" F1 tornado, which had touched down far to the east of the other twisters from that day, at around 8:10 p.m., near Grippen Lake, about 35 kilometres northeast of Kingston.

Lost and found

Severe weather experts work quickly to investigate tornado reports. In most cases, if not all, this involves travelling to the location to assess the damage first-hand.

From this close investigation, the experts can learn two important pieces of information: 1) the pattern of the damage, which will reveal if it was actually caused by a tornado (as opposed to some other weather phenomenon, such as a downburst) and 2) an estimate of how strong the winds were, which allows them to classify the strength if a tornado is confirmed (on the Fujita scale in the past, and now the enhanced Fujita scale).

In addition to this case-by-case forensic work, scientists with Environment Canada - such as Severe Weather Scientist David Sills - are also working to maintain the most complete database of tornado activity in Canada.

It was the effort by Sills and his colleagues, as they combed through the collected reports in both the Ontario Tornado Database (which stretches back to 1792) and the Canada Tornado Database (currently covering 1980 to 2009), that uncovered this "lost" tornado from May 31, 1985.

"The Kingston Weather Office (closed in the 1990’s) investigated a report of damage on 31 May 1985 at Grippen Lake," Sills wrote in an email to The Weather Network. "A short, but very narrow path of damage was found, mainly large trees snapped and uprooted, but a small boat was thrown and cottages were damaged by the falling trees."

According to Sills, the report from the Kingston office did indicate that the damage was caused by an F1 tornado, however there was no indication as to why the report was not included in the official record for the day.

Damage was also reported in the Ottawa Valley later that night, however, it was not attributed to a tornado. Instead, this damage was most likely due to a downburst.

Tornado? Downburst? What's the difference?

Like tornadoes, downbursts can cause significant damage, but they are caused by a very different process than a tornado, and the type of damage they cause is different as well.

When a storm moves into an area with dry air, rain and hail falling from the base of the cloud evaporates before it hits the ground. This process draws a large amount of heat out of the air. The drier the air, the more evaporation, and thus the colder the air will become. Since colder air is heavier than warmer air, this chilled air plummets towards the ground. In extreme cases the winds generated by this plummeting air can reach speeds of over 100 kilometres per hour - the equivalent strength of an F1 tornado, or EF0 tornado under the newer enhanced Fujita scale.

One way to tell a downburst from a tornado is to check Doppler radar signatures, as they show up looking very different from one another. In the absence of Doppler radar, though, the damage pattern will look different as well. Downbursts tend to blow things over all in the same direction, while tornadoes whip debris around it, producing a very distinct pattern.

Why Does This Matter?

Tornadoes are significant and dangerous events, so studying them is of great importance to the scientific community.

However, what difference does it make that one small tornado was added to this record? Why spend time and resources to catalogue and refine databases of Canadian tornadoes, even going so far as to revise events years and even decades after the fact?

For example, according to Sills:

"The 1970 Sudbury tornado used to have an extremely long track in the Ontario tornado database - much longer than any other track in Canada. We went back to the source data and were able to break the one tornado into three much shorter pieces and remove a long section of track where the data were very sparse. That now leaves the Grand Valley–Tottenham tornado from 31 May 1985 as the longest tornado track in Canada at 115 km."

Part of this is to expand our understanding of tornadoes, the conditions that spawn them, how often these conditions occur in Canada, and where they are most likely to form. This helps in forecasting these events, to keep the public safer from harm.

It goes far beyond that, though, as the information being collected is also used for student projects and university-level research, as well as by the insurance and risk assessment industries, the nuclear industry and by provincial and municipal organizations.

The data collected can also be used in climate studies, to reveal how tornado activity may change in a warming world.

Source: Environment Canada