SOME THOUGHTS ON WINTER....

July 29, 2020

Getting into the "dog days" of summer like we are now, our weather tends to grow sluggish and slow down. The jet is at its seasonal weakest as the cold air that powers it much of late fall through spring vacations in Canada. Without the strong thermal contrast to intensify cyclones, late summer storms are fewer and often far between. Severe weather (which was minimal this year) has long since peaked and precipitation episodes now become scattered and hit and miss in nature.

 

For me this is the doldrums, my slow time of year, and while there's always weather, sometimes I have to look elsewhere to find anything exciting. It's now that I start digging around looking for clues to what lies ahead this fall and winter. 

 

For those of you who follow this page, you know that I put great emphasis in sea surface temperatures when it comes to developing long range forecasts. 70 percent of the earth is comprised of water and its well known that the inequity in ocean temperatures drives weather patterns. By looking at similarities in sea surface temperature from previous years you can often get a feel for the cards winter will have to play with. These are known as analogs.

 

One thing that seems likely by the winter is a La Nina. Most of you have heard of El Nino, when the waters of the tropical Pacific are warm, especially off the coast of South America in Chili and Peru. More often than not that brings the Midwest a mild winter with a split flow keeping the worst of the cold in Canada.

 

This year, most of the dynamical models are pointing to a least a weak La Nina. That means tropical ocean waters near Chili and Peru will be cooler than normal. Based on evidence from previous weak La Nina's, climatology indicates right out of the gate that chances for a typical Midwest winter are good and that's a premise worth building around.

More in depth speculation can be attained by looking at global analogs of years with similar sea surface temperatures. I haven't had a chance to research too far back in my comparisons yet but I did reach far enough back to uncover the sea surface temperatures of July 27th, 2013 to those of this year on the same date. There are some striking similarities. Here's 2013

Compare the three areas I have highlighted with where we are at the same period in 2020. 

You can see warm departures in the the North Pacific, off the west coast of Mexico, and much of the Middle and north Atlantic. There's also the cool departures over northwest South America (that's the La Nina look) and some coolness in the Gulf of Mexico. In a general sense, it's very tough to get everything to line up with so much planetary water involved, but dang this is like seeing twins. Without a doubt, at this point in the game 2013-14 has to be considered as an analog for the coming winter..

 

So what do you do with an analog, you throw it in a bag with other similar years and generate a mean look for both temperatures, precipitation, and snowfall. Factors such as the MJO (Madden Jullien Oscillation), EPO (eastern Pacific Oscillation) PNA (Pacific North America Oscillation) will also come into play. Since I don't have all the research completed previous to 2007, all I can show you today is what the winter of 2013-14 looked like in relation to sea surface temperature departures and point to that as a "potential" indicator.

 

One thing's for sure, the 2013-14 winter was a mean one. In Chicago the average temperature from December through March was the coldest on record.

Many cities in the Midwest and Great Lakes had top 5 cold and at least top 10 snow. Detroit had 94 inches of snow and Chicago topped the 80 inch mark. In the Quad Cities, snowfall set a winter record (December-February) with 53.8 inches eclipsing the legendary winter of 1978-79. 

So what have we revealed here? Nothing concrete I can assure you, especially in late July and without other considerations in loading patterns and sea surface temperatures. However, this is an eye opener for starters and it does give me hope that this winter will have a little kick. The coming La Nina and a strong SST analog is certainly a good foundation to build on. I very much doubt it ends up like 2013-14 but even if it's 2/3rds as good it would be a keeper! Roll weather...TS

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© 2019 Terry Swails