Chicago’s winter weather is impacted by a range factors–the presence of a La Nina can be among them. A La Nina is BY NO MEANS the only factor which contributes to character of a particular winter’s weather—but history has shown it can have an impact.

A La Nina is declared when ocean temps cool along a vast stretch of the equatorial Pacific west of South America. La Ninas typically involves an increase in the prevailing easterly surface winds which blow along and either side of the equator. This typically happens every 3 to 5 years.

When equatorial winds strengthen, warm surface water is pushed westward and away from South America which, in turn, leads to the upwelling of colder, deeper water along the South American coast.

The easterly winds then blow this cool water westward toward the International Date Line in the western Pacific producing a vast swath of cooler than normal ocean water. This, in turn, cools the air above it impacting steering winds across the region.

And since the atmosphere surrounding our planet is one vast, interconnected system, the impacts lead to global changes far from the cool ocean waters which produced them.

We have an exceptionally persistent La Nina underway in the equatorial Pacific. It’s being referred to as a “TRIPLE DIP LA NINA”.

Dr. Brian Brettschneider, National Weather Service climatologist based in Alaska posted the following interesting and timely analysis today (Wednesday 10/12):

“This winter’s La Nina is forecasted to be on the edge of moderate strength (ONI ≥ -1.0C). How does precipitation do in moderate and strong La Nina winters? Of the 16 events since 1925, most were drier than average along the southern half of the CONUS. Mixed signals in the north.”
Also, check out the posted National Weather Service depiction of frequently observed La Nina winter weather trends.

By the way, check snow has come to southern Alaska. And our 49th state’s first sub-zero temps occurred in its northern reaches Wed morning. Check out the pictures of the fresh accumulation of snow in south central Alaska posted by Dr. Brettschneider.

COMING IN THE WEEKS AHEAD: I interviewed Dr. Brettschneider during our trip to Alaska the week before last for our upcoming CLIMATE CHANGE SERIES and PROGRAM. You’ll see that interview and our interview with other climate scientists, including Dr. Don Wuebbles, nobel prize winning climate researcher out of the Univ of Illinois as part of our upcoming programs.
Alaska and our planet’s arctic regions are experiencing climate change at a pace four times that of other regions of the planet. The state’s glaciers are in dramatic retreat. Changes which once took tens of thousands of years to occur are occurring in a single generation. We’ll show you–plus look at the alarming drop in Lake Mead’s water level, the country’s largest reservoir in Nevada created with the construction of Hoover Dam across the Colorado River outside Las Vegas–concerning because it’s the primary water source for that region and the source of hydroelectric power and we’ll share conversations we had with a range of scientists at NASA’s Goddard Space Flight Center in Greenbelt, MD (outside Washington D.C.) where satellite are designed and build to monitor the planet’s ice loss and sea level rise—plus look at work being done by United Airlines to move to slash carbon emissions through the development of cleaner fuels and the introduction of electric aircraft for the company’s shorter regional runs.

Here’s the schedule for our upcoming climate change reports and our special program which airs in several weeks–and there will be more to come in the weeks ahead:

  • Monday, October 31, 9P
    • Climate Pkg 1 – Intro in Alaska; NASA Goddard
  • Tuesday, November 1, 9P
    • Climate Pkg 2 — Lake Mead/Vegas Water Crisis
  • Wednesday, November 2, 9P
    • Climate Pkg 3 – Alaska Glacier Melt
  • Friday, November 4, 7-7:30P
    • Forecast: A Fragile Climate½ hour WGN Films Special Presentation