article_snippet.sent: A recent set of studies published in Geophysical Research Letters by Bond's group points to a high-pressure ridge over the West Coast that has calmed ocean waters for two winters.
article_snippet.sent: That same persistent jet stream pattern has allowed cold air to spill into much of the Midwest and East.
article_snippet.sent: That same persistent jet stream pattern has led to the record cold and snow in the Midwest and Northeast over the last two seasons with record snows we have seen in Boston and Detroit, and the most snow we have seen in decades for cities such as Chicago.
article_snippet.sent: That same persistent jet stream pattern is confusing the experts.
article_snippet.sent: There are some that think it might be a Pacific Decadal Oscillation, a long-lasting El Nino-like pattern in the Pacific.
article_snippet.sent: Dennis Hartmann, a professor of atmospheric science at the University of Washington, doesn't believe the answer is clear.