Texas floods showcase difficulty of predicting severe weather, experts warn

Climate change and weather pattern experts are pointing to the flooding disaster in Texas as a sign of what's to come closer to home, and warning that communities need to be better prepared for severe weather.

At least 104 people are confirmed dead after a flash flood ripped down the Guadalupe River, with the search continuing for more people who are missing. Some of the missing are children, including 10 girls at Camp Mystic, an all-girls summer camp in Kerr County, central Texas.

"With more greenhouse gases in the atmosphere, we are seeing more and more of these catastrophic events that we never expected to happen,"  Reza Najafi, a Western University professor and expert in hydroclimatic extremes said. 

As new weather patterns emerge because of the rapidly changing climate, it is difficult to rely on historical data to make predictions, he said.  

London saw its worst flooding in 40 years in 2018, Najafi pointed out, when the Thames River overflowed its banks in Harris, Thames and Gibbons parks. No one was injured but there was significant damage to the grounds and park facilities. 

Rising temperatures, in particular, can lead to higher amounts of heavy rainfall and London is experiencing that already, said Gordon McBean, a climatologist at Western University. 

"The fact is that the climate system is changing, and Canada is warming roughly twice as fast as the global average." 

A heat warning was issued over the weekend for July 5 and 6 with temperatures over 30 degrees, and days like those are going to increase significantly, Bean said. While London is used to getting about 10 of these hot days over the summer, it's expected to increase to 40 by 2050, he said, and more  moisture will evaporate into the cloud system, taking a lot of energy up there with it. 

"It shoots up into the atmosphere and that vertical motion is created," he said. "Eventually, that motion will turn around and come down as precipitation and wind events."

Detection and response methods leave room for improvement.

Awareness, preparation and warning systems are crucial when severe weather occurs, both Najafi and McBean agreed.

Safety measures must be proactive, McBean said. There needs to be more coordination between the experts sitting in forecast offices and members of the community to get information out to the public, so people can make their homes and properties more resilient to disasters. The floods in Texas revealed some of the shortcomings in how agencies currently deal with climate threats, he added. 

Many received warnings during the middle of the night, others received no warnings at all, and some areas did not have alert sirens, Najafi said, highlighting a few of the issues he saw. While some people may have noticed the water rising, he added, they might have been caught off guard by how quickly it progressed, leaving them unprepared to respond.

"Preparation requires education, it requires planning and drills." 

Early detection of severe weather is also a key part of mitigating risk. The models used by meteorologists are generally very capable, but there is still room for improvement, Najafi said.

Models can predict heavy rainfall generally in many areas, but it's still challenging to predict the magnitude, or which exact regions might be affected, he added. 

The lake effect is a good example, Najafi said. In the London area, cold air moving over Lake Huron can cause large amounts of precipitation over land, but many models, particularly climate change models, do not capture it very well, he said. 

Forecasters should also be trained to look not only at the history of weather events in their own regions, but also at how storms have happened further south, McBean said. This will allow them to make more effective forecasts as climate change disrupts longstanding weather patterns, he explained. 

"As the climate warms, the patterns of severe weather events will be moving northward," he said. "We'll see more heavy precipitation events at latitudes that we probably haven't seen before, or at least in human times."