How the Fort McMurray Blaze Grew Into a Monster Firestorm

Flames engulf trees along a highway near Fort McMurray, Alberta, Canada, on May 6, 2016. Image credit: Cole Burston/AFP/Getty Images

Fort McMurray is burning. A wildfire began just south of the Canadian city on May 1, quickly growing into an inferno that crews couldn’t contain. Local officials ordered the entire city of 80,000 evacuated as the fire grew.

While most drivers attempted to evacuate Fort McMurray—many were stranded for days on the area's only highway—others waited for clearance to take firefighting supplies into the town on May 05, 2016. Image credit: Scott Olson/Getty Images 

This was no small task, given that Fort McMurray is in far northeastern Alberta, hundreds of miles away from Edmonton, the nearest large city. Officials aren’t yet sure what caused the fire, but weather certainly played a large role in letting it become a firestorm that by today, May 6, has burned an estimated 245,000 acres—10 times as much as just two days ago. 

The climate of this part of interior Canada exposes residents to huge variations in weather conditions throughout the year. The region typically sees a brutally cold and snowy winter followed by a quick spring and a warm summer. Fires are a natural and healthy part of life in forested areas, but sometimes abnormal weather can exacerbate (or even cause) these burns and turn them into raging infernos.

Home foundations are all that remain in a residential neighborhood destroyed by a wildfire on May 6, 2016 in Fort McMurray. Image credit: Scott Olson/Getty Images

A confluence of two different weather patterns allowed the Fort McMurray fire to grow into a monster. The first is the long-term weather patterns influenced by El Niño, an unusual uptick in sea surface temperatures in the eastern Pacific Ocean near the equator. The abnormally warm water during an El Niño alters global weather patterns, and we would expect western Canada to be abnormally warm and dry during what is typically a cold and snowy winter. Temperatures in Fort McMurray have been warmer than normal in recent months, and the relative lack of rain and snow in this region of Canada this winter has left the ground and vegetation dry. Officials declared the start of wildfire season in Alberta one month early due to the growing drought.

A weather model image showing surface temperature anomalies (°F) across North America on Wednesday, May 4, 2016. Image credit: Pivotal Weather

In addition to the long-term conditions, the weather over the past week allowed the fire to grow from a nuisance to a disaster of extreme proportions. A large ridge of high pressure in the upper levels of the atmosphere has covered most of central North America in recent days, allowing very warm weather to stretch deep into Canada. Temperatures climbed into the 80s and 90s well into Alberta at the height of the early-season heat wave. Moist air did not accompany the heat wave, so not only did it get very warm but it was also very dry. The lack of humidity helped dry out any vegetation that was already parched, and it set up a situation where even a small fire could quickly intensify. Gusty winds helped the flames spread at an unmanageable pace.

Charred trees are seen along a highway near Fort McMurray on May 6, 2016. Image credit: Cole Burston/AFP/Getty Images

Once the fire grew large enough, it began to generate its own favorable conditions sort of like a microclimate in the immediate area around the blaze. The heat of the fire caused local temperatures to soar, making the air drier and causing air to rise rapidly. This dried out the surroundings even more and created gusty winds that fed and spread the flames. This vicious cycle, usually present in all large wildfires, continues until weather conditions improve or the fire encounters unfavorable terrain to burn, then it starts to die down with the help of nearby fire crews.

On Wednesday, local officials said that the blaze had destroyed at least 1600 homes and businesses, and the toll has likely risen since then.