“Temperatures across the Northeast have been unusually cool, and they have been unusually hot across the northwest.  A strange jet stream is behind the flip-flop between summer conditions in the two northern corners of the country. The polar jet stream is the prevailing band of wind that blows west to east across the upper half of the U.S. in summer. (There is a subtropical jet, also, that typically crosses northern Mexico).  We often see the jet stream depicted on TV weather reports—that big, wavy line across the U.S. and Canada that bends south then north then south again. Low-pressure weather systems, sometimes called cold fronts, ride along the jet stream, bringing us much of our daily weather. But this summer the polar  jet steam seems to be somewhat flattened out, and it’s been in that position more than usual.”

Tags: physical, weather and climate, seasonal.

Source: blogs.scientificamerican.com