‘Omega block’ behind European heat wave – could it happen in Canada? – Nationally
The deadly heat that is slowly boiling over western Europe this month is being driven by a weather pattern known as the Omega block, which scientists say could become more common around the world – including in Canada.
The heat wave dropped temperatures up to 18 C above their seasonal average, according to the Reuters Climate Monitor. Hundreds of people have died, including at least 40 in France who drowned while swimming to escape the heat, according to officials.
“In the study region, this heat wave is the worst on record,” the World Weather Attribution group of climate scientists said in an analysis on Friday.
Here’s what you need to know about Omega block, and whether climate change is to blame.
The Omega block gets its name from the way the pressure systems appear on the weather map, resembling the Greek letter “Ω.”
In the case of Europe, a warm high pressure wave has settled in the affected countries, with low pressures on both sides of it – the Atlantic coast to the west, and parts of eastern Europe on the other side.
The warm air is trapped or “blocked” within that structure, as opposed to normal conditions where the jet stream carries weather systems from west to east.
“Because you have this high pressure system sitting there in the center, you have very stable and warm air because the heat is being transported northward in that area,” Gordon McBean, a professor of climate and environmental studies at Western University, said in an interview.
“Then it builds up over time.”
Omega blocks usually last between three and 10 days, but can sometimes persist for weeks.
Map showing the forecast maximum temperature from June 25-27 in Europe.
The Associated Press
What happens during Omega Block?
Countries including Spain, France and Germany have been seeing hot and dry conditions. Because high pressure also suppresses cloud formation, there is little relief from the sun.
France recorded its hottest temperature of 43.8 C in the small southwestern town of Pissos on Wednesday.
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That day was the hottest day across the country in history, according to the weather agency Meteo France, which said the average temperature measured at 30 French weather stations during the day and night reached 30 C for the first time.
Saarbruecken, a German city near the French border, broke the national temperature record on Friday at 41.3 C.
Low-pressure regions on the side of the heat wave, on the other hand, are more likely to see cool and wet conditions.
Britain is caught between high and low pressure systems, with extreme heat in the south and east and cooler temperatures in the north and west, according to the UK Met Office.
However, forecasters added a red heat alert for Friday after the temperature in Suffolk, England, reached 37.3 C, marking the hottest June day the country has ever seen.
Can Omega block happen in Canada?
Yes – and it has happened this year.
Meteorologists at the Weather Network say the Omega block is responsible for the late May heat wave in parts of Alberta, Saskatchewan and Manitoba. Most of the region saw highs of up to 35 C.
Another Omega block was also behind the record-breaking 21 C reported by Saskatchewan in January 2024, the network said.
McBean said Omega blocks can be predicted with high confidence before they occur, noting that one of the patterns of severe weather has become more common in recent years.
What role does climate change play?
The World Weather Attribution analysis said the European heat wave “would not have happened” without human-caused climate change.
The same heat wave in the same month 50 years ago was about 3.5 C cooler than this one, scientists say.
The analysis added that last week’s temperatures were 100 times higher than in the previous two decades.
That is due to the increase in global warming caused by greenhouse gas emissions.
The European heat wave also happened on the fifth anniversary of the dangerous heat that scorched British Columbia and the Pacific Northwest of the US in 2021, which killed more than 600 people in the province alone.
McBean said it is important for people and officials to be aware of the increasing frequency of such heat events and prepare accordingly.
“These are conditions that unfortunately lead to death (and) significant economic costs, and they will increase in the future,” he said.
“We need to adapt our ways of dealing with it,” he added, from improved warning systems to ensuring that homes and buildings are designed with brain cooling in mind.
-via files from the Associated Press and Reuters
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