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How did smoke from the West Coast fires make it to New England? It all has to do with the jet stream

A seagull flew past a fading sun that is viewed over Boston on Tuesday as the smoke from the West Coast fires dulled the skies.Stan Grossfeld/ Globe Staff

For more than a week we’ve seen horrific pictures from the West Coast of unbearable air quality and catastrophic damage from wildfires. On Monday the smoke began to arrive in New England, and yesterday we actually witnessed the sun noticeably dimmed by smoke.

This morning as the sun rose, it once again took on an orange glow, an indication of smoke in the atmosphere. You might wonder how this all got here, and the answer is the jet stream.

In a view of Boston's Back Bay skyline from a Coolidge Corner rooftop, the sun takes on a haze due to the smoke.Lane Turner/Globe Staff

As the fires raged last week across the West Coast, high pressure trapped the smoke in that area of the country, but eventually the high pressure system relinquished its grip and the jet stream has caught the smoke and pulled it toward the east.


A changing jet stream will eventually push the smoke out of New England late this week.Tropical Tidbits

It actually isn’t that uncommon to see smoke from forest fires hundreds, if not thousands, of miles away here in New England. After all, the atmosphere doesn’t know borders, and it’s all basically a ribbon of air circulating the planet. We often have smoke from Canadian wildfires in spring and early summer.

There’s all sorts of ways to look at the smoke, including through the satellite. The visible satellite loop below shows the smoke crossing New England this morning. If you look closely you can see the difference between smoke and clouds, because the smoke has more of a flat look to it. Smoke in some ways looks more like fog would look on a satellite photograph, with a flatter appearance.

Smoke continued to cross the area this morning. Notice the thickness isn’t consistent in all areas.COD Weather

The poor air quality out west might make you wonder whether or not we’re having the same issues here. The answer is no, our air is fine. This is because our smoke is at a much higher level of the atmosphere than what was occurring out on the West Coast.

Air quality in New England will continue to be in the good range this week.EPA

In that part of the country the smoke originated at the ground, permeated all levels of the atmosphere, and that eventually moved to the east. For us to have problems, the smoke would have to fall to the ground where we all live and breathe, but that’s not going to happen. If you look at the graphic below you can actually see the layer of smoke starting as low as 5,000 feet, but really concentrated about 18,000 feet up, far higher than where we live.


A cross section of smoke in the atmosphere over Greater Boston.NOAA

One thing the smoke is able to do at this level of the atmosphere is prevent the full amount of solar radiation from reaching the ground. This is one of the reasons why our high temperature yesterday of 61 degrees was slightly below what was forecast in the mid-60s. The computer models don’t do a good job integrating something as fleeting as smoke into their forecasts.

Eventually our winds will turn more northwesterly at higher levels of the atmosphere and the smoke will dissipate. I expect this to happen Thursday and Friday with the passage of a cold front.

The smoke forecast shows the core of the smoke being pushed south late Wednesday as Canadian air moves into the upper midwest.NOAA

Along with less smoke this weekend will come the feeling of October. We’ll have a colder-than-average few days ahead, and I bet some of you will be putting the heat on before the weekend is out.

Follow Dave Epstein @growingwisdom.