© 2019 Terry Swails

FROSTY AND FRISKY, A PREVIEW OF THE WINTER AHEAD?

November 10, 2018

The last winter that was tough by my standards here in the central Midwest was 2013-14. That year was dominated by prolonged cold and included a couple stratospheric warming events that forced the polar vortex into the Great Lakes. It put the eastern U.S. into a deep freeze. It was so cold that 88% of the Great Lakes froze up. So too did Niagara Falls.

An Icy Lake Michigan surrounding Chicago in 2014.

Milky cold air on the hi-res satellite pressing southward to the Gulf of Mexico.

The frigid early season air we are currently experiencing made me look back at what drove the cold in 2013-14. Interestingly enough, the severe winter (December–March) in the Midwest was dominated by a persistent atmospheric circulation pattern anchored to a North Pacific Ocean that was much warmer than average. Strong teleconnections associated with the eastern Pacific oscillation (−EPO), tropical Northern Hemisphere pattern (+TNH), and the second-lowest Hudson Bay 500mb height field, are the primary indicators that led to severe winter weather across the eastern United States according to Alan Marinaro of Northern Illinois University. The abstract is entitled The North Pacific–Driven Severe Midwest Winter of 2013/14.

 

He went on to write, "Unlike in previous cold and snowy Midwestern winters, Atlantic Ocean blocking played little to no role in the winter of 2013/14. The primary atmospheric feature of the 2013/14 winter was the 500mb high pressure anchored over the North Pacific in response to the extremely warm sea surface temperature anomalies of +3.7 standard deviations. Only one other severe Midwestern winter (1983/84) since 1950 featured a similar Pacific blocking. The accumulated winter season severity index, which is a metric that combines daily snowfall, snow depth, and temperature data for the winter season, was used to compare the 2013/14 winter with past winters since 1950. Detroit, Michigan, and Duluth, Minnesota, experienced their worst winter of the 55-yr period. Seven climate divisions in northern Illinois, eastern Iowa, and parts of Wisconsin experienced record-cold mean temperatures".

 

Needless to say I had to dig up the sea surface temperatures of 2013 and compare them to this winter. Look what I came up with. Strong similarities in the North Atlantic, the Gulf of Mexico, and the Western Atlantic.

This makes 2013-14 an analog for the winter of 2018.  That year the teleconnections of the PNA (Pacific North America) and the TNH (Tropical Northern Hemispheric) were positive. The EPO (Eastern Pacific Oscillation) was negative. Those are the predominate phases I expect to see those teleconnections in this winter.

Why does this matter. Well, lets look at what happened in the 2013-14 winter. The graphics courtesy of Alan Marinaro's abstract.

 

Temperatures: As you can see in my area temperatures were the coldest of record.

Here are the specific departures.

Snowfall: Most of the Midwest had above normal snowfall, in some areas 2-3 times above normal in the Great Lakes.

 

This is the 500mb jet stream pattern that prevailed most of the winter. You can see the high pressure associated with the warm water in the north Pacific. That drove the trough which delivered the prolonged cold. That to me is key to 2018-19.

In closing, it's important to say that no matter how close in SST's, no two winters are the same. There are many other factors that come into play including the low solar period we are in and the weak Modiki El Nino. It just seems to me this is more evidence that supports my contention this winter will end up frosty and frisky. Roll weather...TS

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