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Cross Hemisphere ridge


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I'd like to know more about this ridge that starts off the west coast of Mexico and continues through the North Pole. This only started happening in the last 5 years, and is being modeled to continue through most of January. Winter 13-14 had a long period of this, but 17-18 will be longer. 

1c.gif

I guess more specifically -- why is the NPH so strong?

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The pattern appears to be a strong +DA (dipole anomaly), e.g. the second mode of the Arctic Oscillation's EOF (see fig 2: http://onlinelibrary.wiley.com/doi/10.1029/2008GL036706/full).

This article posits that sea ice loss on the Pacific side generates a teleconnection that results in this sort of pacific ridging behavior: https://www.nature.com/articles/s41467-017-01907-4

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36 minutes ago, raindancewx said:

This pattern, if you look at conditions in the big drought in the West in 1947-1957, happened fairly frequently, had ten-below average water years in a row from July-June, for 1947-48 to 1956-57.

Perhaps a perfect storm of natural and man-made forcings conspired to bring about an early demise of arctic ice cover.

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STkzxUr.png

For reference, most of NM (non-mountains) gets <10" per year. So 3-4" below normal for a decade is crazy.

For what its worth, photographs of the Arctic in the air-force did imply that during the end of the warm AMO/warm PDO peak (1928-1945) sea ice extent may have been as low as 4.5-5.0 million km^2 based on comparisons to today - that's still above the levels of say, 2012 by quite a bit, but it would have been similar to years like 2017. Some of the winters in the 30s/40s are pretty similar to recent winters. 1931-32 v. 2016-17, 1930-31 v. 2015-16 come to mind, and then others in the mid-40s too. The intense cold in the NW in 2016-17 is similar to a lot of winters in the 40s in particular. 

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2011
Now, go back before this date and you'll never see a ridge south of the west coast connected to Russia through the Pole. 

77b.gif

Even at this start, there are significant differences to the now (+PNA way west, cold that far south into the Gulf- it wouldn't happen that way, in other words so much -anomaly). 

[If someone can help my ability to upload images on this board it may be helpful for future reference] 

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Quote

 

So far I have to rate this thread as a failure. I have seen zero incidents of any of the images you have shared that the ridge has spanned across the equator. Maybe you have a different definition of hemisphere than I do though.

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On 4/2/2018 at 11:30 AM, bowtie` said:

So far I have to rate this thread as a failure. I have seen zero incidents of any of the images you have shared that the ridge has spanned across the equator. Maybe you have a different definition of hemisphere than I do though.

It's a rare pattern that has happened since 2009

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