NEW YORK — Smoke from the Canadian wildfires has plagued the tri-state area for days.
The prolonged problem is the result of a weather pattern that occurred for those in the Great Lakes, the Northeast, and the Mid-Atlantic.
We are under a weather pattern known as “Omega Block” for meteorologists. Simply put, it’s a large ridge of high pressure over central North America with flanking areas of low pressure over the east and west coasts.
Another weather system that has fueled the Canadian-American smoke, a low-pressure system over Maine and Nova Scotia, “will probably be circling for at least the next few days,” said Bryan Ramsey, a meteorologist with the US National Weather Service.
“Conditions are likely to remain unhealthy, at least until the wind direction changes or the fires are out,” Ramsey said. “Since the fires are raging, they’re really big, they’re probably going to go on for weeks. But really it’s just going to be the wind change.”
The alignment of these high and low pressure systems causes the jet stream, the river of air that rushes at about 30,000 feet, to become severely deformed. The shape of the flow resembles the Greek letter omega (Ω).
The warped jet stream ends up creating the equivalent of an atmospheric traffic jam. It stops the migration of high and low pressure systems, leading to stagnant weather patterns.
In our case, the low pressure system along the East Coast is perfectly positioned to transport the smoke from the Quebec wildfires directly to the New York City area, day after day, after day.
Smoke has been a problem since Tuesday, but you may have noticed that it’s worse in the afternoon and evening compared to the early morning. It’s not your imagination, it’s something real. But why does that happen?
Much of the smoke from wildfires is carried by the wind, several thousand feet high. During the day, as temperatures rise, the atmosphere becomes unstable. Pockets of warm, buoyant air at the surface begin to rise through the atmosphere, much like a hot air balloon rises.
To fill the void, cooler air from above mixes with the surface and takes its place. A vertical circulation develops which is a very common phenomenon, but when there is smoke above it also mixes down to ground level. That’s a big reason smoke concentrations are worse in the evening and at night.
The atmosphere stabilizes and vertical mixing ceases as temperatures cool overnight, allowing smoke to partially dissipate. In the morning the haze may still be there, but it is less severe.
To end the smoky haze over the tri-state area, one of two things must happen. Either the fires go out or the wind patterns change and blow the smoke away from us.
This week, it appears that a change in the wind pattern is likely to occur first. The area of low pressure over the East Coast will move in as we go through this weekend. This comes with a change in wind direction which we think will clear out most of the smoke.
As of Thursday afternoon, it looks like the air quality this weekend will improve to moderate, which is certain.
Jennifer Peltz, Rob Gillies and Michael R. Sisak of the Associated Press contributed to this story.
