Kinks in the Jet Stream Meant Two Very Different Junes for Eastern and Western US

Throughout June, two very different stories played out throughout the contiguous United States: while the drought-stricken West succumbed to an intense heat wave, those on the East Coast were bombarded by a series of summer thunderstorms.

The reason for this, according to a NOAA report, lies in a series of kinks that developed in the jet stream. Called troughs and ridges, the former refers to a low-pressure area that allows the jet stream to dip southward. A ridge, on the other hand, is characterized by a large portion of above-normal atmospheric pressure that pushes the jet stream northward of its usual position.

Since early June, the eastern half of the United States has sat sandwiched between two ridges - one over the West and the other over the western Atlantic.

"Meanwhile, a persistent upper level trough pulled the jet stream south of its normal position over the East," explained David Unger, a meteorologist from the NOAA Climate Prediction Center. "In early June, we saw the jet stream steer Tropical Storm Andrea northward, drenching the eastern seaboard. "

This same trough persisted throughout much of June, Unger said, ultimately bringing wetter-than-normal conditions for most areas east of the Mississippi River.

The West, in contrast, spent much of June under an upper-level ridge, resulting in unusually wet weather for Montana and southern Alberta and causing severe flooding in the Canadian city of Calgary.

With all the moisture funneled north and east, the Southwest sat gasping for water.

All told, the majority of Southern California, Arizona, Nevada and Utah received less than 10 percent of normal rainfall and in some places far less throughout the month. Furthermore, an extreme heat wave worsened drought conditions for the region, even in the desert where little precipitation is typical during this time of the year.

Such dry weather invariably has a human toll, though in this case it seemed especially high. The intensity of the heat and lack of moisture were two driving factors in what turned out to be Colorado's most destructive fire in state history as well as the fire in Arizona that killed 19 firefighters. In all, as of July 9, the National Interagency Fire Center reported 22 total active fires occuring throughout the United States.