There is a weather pattern that re-occurs every 7 to 10 years or so, where a massive ridge lodges itself over the western U.S. and the jet stream dives down over the east, bringing cooler and/or wetter than normal summer weather to the Atlantic. It seems to persist for weeks at a time. We've been in that pattern big time for the past several years. We had a pattern similar to this in the summers of 2000 - 2004. Does anyone know what causes this pattern? Is it an El Nino or La Nina pattern? Is there some other phenomenon (water temperature in the Atlantic) that causes this to happen? Attached is a typical map of what I'm talking about.
