The glorious September-like weather that has enveloped Washington in mid-August is the result of an unusually strong high-pressure system that has strayed from its normal Canadian haunts to New England.
Remarkably, the below-normal temperatures and humidity probably will continue in the Washington area through next Wednesday, according to National Weather Service forecaster Gary Ellrod.
The area's weather during August is usually controlled by a less benign high-pressure system that forms over the Atlantic Ocean and is known as the Bermuda high, Ellrod said. The Bermuda high sweeps hot air, dripping with moisture, from the Gulf of Mexico to Washington, where it generates perspiration, foul moods and travel plans.
But the high-pressure system that has descended from Canada is instead bringing cool, dry air from the north. "Essentially, we're getting the weather that should be going to upstate New York and New England this time of year," Ellrod said.
The Bermuda high is still out there, he said, but is weaker and centered farther south than normal. The high-pressure bruiser from Canada has kept the enervated Bermuda high from setting up shop at its usual site. While it was at it, the Canada high deflected Tropical Storm Dennis well off the mid-Atlantic coast, where it strengthened into the season's first hurricane.
The storm claimed three lives in a sweep up the lower East Coast, but Ellrod said it should pose no further threat to land.
The Canada high's journey southward is the result of a complex chain of meteorological events, the forecaster said, that begins with an abnormal low-pressure area over Alaska and includes another unusual high over the Plains states. The Canada high should prove "pretty hard to dislodge," he said. While rain may occur during the next week south of the Washington area, none is expected here.