[bthompson1234]

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.

 

 TypicalPattern.jpg   146.42KB   0 downloads

 

[Andie]

I can't answer your question. Perhaps Phil will weigh in.
But I agree that there is a pattern. We experience it here in Texas every 8-10 yrs. I recall our last one with moisture and snow in the winter.

This morning we have rain agin and 42*. A 33* wind chill. Crazy for Mid October.

[Phil]

It’s probably a combination of solar cycle/IPWP vacillations and other low frequency system resonances modulating the state (and seasonality) of the extratropical circulation cells/annular mode(s). Complicated stuff..as there is no efficient way to determine exactly why these “cycles” exist. But they do exist, for whatever reason.

[Dan the Weatherman]

It seems that this Western ridge / Eastern trough pattern has become even more persistent than usual over the last 5-6 years during the winter months, causing worsening drought conditions over an increasingly larger area of the west. I am really getting tired of this pattern because Socal has been overall very dry over this 5-6 year time period and am ready for a switch to wetter winters for a change.