Seventy-Two Hours Under the Heat Dome
The high winds that make up the polar jet stream encircle the Northern Hemisphere like a loosely draped rope. There are typically four or six curves in the rope, the result of the temperature differences between the equator and the North Pole. The pattern of these curves is usually predictable, the weather associated with them—warm or cold spells, rain or snow—sticking around for a week or two, unless a significant event disrupts it. On June 20th, a tropical depression that appeared in the western Pacific, near Micronesia, may have been the beginning of such a disruption. The next day, as the tropical depression moved northwest, past Guam, it gathered enough force—sustained winds of forty miles per hour—to qualify as a tropical storm. It turned north on June 22nd, and as the storm, called Champi, neared Japan it became a typhoon, with winds as strong as ninety-two miles per hour. As the typhoon moved farther north, though, it weakened and then disappeared altogether on its way toward Alaska.
Typhoon Champi caused no serious damage and no loss of human life. But a number of atmospheric scientists believe that it may be what gave the jet stream a snap. After the storm diminished, its force continued on, crimping the jet stream into a sharply curved band, or what meteorologists refer to as an omega block, because it resembles the Greek letter. This led to what’s called, colloquially, a heat dome, a high-pressure system in which hot air is trapped over a single geographic area. It stalled over British Columbia, Washington, and Oregon, sealing in the heat.
