Why the red sky? Tri State's dangerous haze, explained

 It's been the talk of the town this week. Thick smoke from wildfires in Canada created the stunning headlines on Wednesday, proclaiming (correctly) that, for a time, New York City had the worst air quality in the world. 

Unaltered images of an orange sky above the Queensbridge Houses on Wednesday.
Photos courtesy of Joseph Kurtek

The bad air quality didn't just impact New York. In addition to the Yankees game, the Phillies also postponed their matchup at Citizens Bank Park due to the hazardous air quality, and in my hometown of Bethlehem, PA, the Air Quality Index briefly topped out at 340. For context, "Good" air quality has an AQI of 50 or lower. 

Hazardous air over Bethlehem, PA on Wednesday.

Thanks for the photo, Mom!

Over 8 million acres have burned so far in Canada, and over a half-million acres have burned in Quebec, the province directly to our north. Most of the active fires are at least 500 miles away from the Tri-State area. So, why is so much of the smoke ending up here? Not surprisingly, it's our current weather pattern that's to blame. The satellite image below shows yesterday's smoky plume curved alongside a deck of cloud cover in New England: 

Image from GOES-East of the smoke enveloping much of upstate NY and eastern PA on Wednesday.
Image credit: NASA

Those clouds are from an area of low pressure sitting over the Canadian Maritimes. Meteorologists call setups like these "quasi-stationary" because little to no movement of these systems is happening in the short term. At the same time, an area of high pressure to the north of the Great Lakes was exacerbating the scenario, concentrating the smoke due south and southeast, causing it to beeline to the Tri-State. You can see the setup on the surface map below: 

Notice the location of the isobars, or lines of constant pressure, in eastern Canada.  They are close together and oriented north to south. When isobars are close together, it indicates a stronger wind than when they're spaced farther apart. And, with high pressure to the west and low pressure to the east, it's like a superhighway for Quebec's wildfire smoke to cruise into our area. 

The smoke doesn't even have time to loft high into the atmosphere; instead, those winds carry the hazy plume near the surface for hundreds of miles. This persistent pattern is finally expected to break by Saturday, as the storm over the Canadian Maritimes moves eastward and the smoky superhighway from Quebec comes to an end. 

If you want to monitor the wildfires in Canada, including hundreds more active fires burning in the western half of the country, go to the Canadian Interagency Forest Fire site. And there are many resources for monitoring air quality; AirNow is a comprehensive resource from the EPA.