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Issues Of The Environment: La Nina And A Winter Weather Outlook For Washtenaw County And The Region

Jan 6, 2021

Dr. Ashley Payne, assistant professor of climate and space sciences and engineering at the University of Michigan.
Credit University of Michigan College of Climate and Space Sciences and Engineering / clasp.engin.umich.edu

One of the few certainties about weather is its uncertainty.  So far, the winter of 2021 is off to a rather mild start.  But, the weather phenomenon known as "La Nina" and other factors could bring  serious snowfall to the region.  In this week's "Issues of the Environment," WEMU's David Fair explored the possibilities with Dr. Ashley Payne, assistant professor in climate and space sciences and engineering at the University of Michigan. 


Overview

  • Winter 2021 is off to a mild (and very dry) start, with unseasonably warm temperatures and almost no snow in Southeast Michigan, but weather experts expect atmospheric conditions will favor a stormy winter.  Some meteorologists are suggesting conditions are right for a “big one,” similar to the epic storm of 1978.
  • La Nina is in full effect this year, typically bringing stormier winters.  The big question is: will that storm track be a little north or south of us?  That is a huge question because, if the storm track is north of us, that means more rain than snow.  However, if the storm track is farther south, then that would mean we get clobbered with a lot of snow.
  • WDIV meteorologist Paul Gross points out, “There’s one more factor to consider: global warming. La Nina years are generally colder years for the planet, while El Nino years are warmer years.  However, as a direct result of the warming climate, La Nina years are now warmer than El Nino years used to be.  So these La Ninas we deal with today aren’t “our grandparents’ La Ninas.”
  • Ashley Payne is an Assistant Professor in Climate and Space Sciences and Engineering at the University of Michigan.  She studies both weather and climate change, and she offers insight into how the two are playing out in our winters. 
  • Education: Ph.D. Earth System Science, University of California – Irvine (2016). 
  • Research Interests: Climate variability and change, large-scale atmospheric dynamics of landfalling atmospheric rivers and precipitation and convection representation in climate models. 
  • Science communication. (Source: *directly quoted* https://clasp.engin.umich.edu/people/ashley-payne/)

La Niña (from the climate prediction center at weather.gov)

La Nina is ongoing heading this winter with cool anomalies noted in the sea surface temperature in the central and eastern equatorial Pacific.  The typical coupled atmospheric processes have been observed as well.

As a result, La Nina will be a key driver for the wintertime atmospheric circulation pattern, with implication on the local conditions on the Great Lakes.  In the typical La Nina wintertime setup, blocking high pressure develops over Pacific Ocean which sets up a ridge over the eastern Pacific and western United States. Downstream of this, a longwave troughing pattern is typically favored over the eastern US.  This would point to a more active winter for the Great Lakes with the jet stream helping to direct numerous storm systems through the region.

Historical La Nina winters (that also account for climate trends in recent decades) show that approximately 50-60% of them had higher than normal precipitation across southeast Michigan, and about 40-50% show higher than normal snowfall. 

January

Temperatures: near normal

Snowfall: above normal precipitation; near to above normal snowfall

February

Temperatures: near normal

Snowfall: above normal precipitation; near to above normal snowfall

(Source: https://www.weather.gov/media/dtx/climate/Seasonal%20Outlooks/DTX_Winter2020-2021_Outlook.pdf)

We have the ingredients for a 1978-style blizzard this winter

While it’s not in the cards right now, we do have the weather elements it would take to have a 1978 brand of blizzard this winter.  Ultimately, the timing would have to be just right.  What would it take to have the big one in the world of Great Lakes blizzards?

Firstly, we would need a heavily moisture-laden storm system.  Those types of storm systems come from the southwest.  As the storm moves out of Texas and north of the Gulf of Mexico, the humid air from the Gulf works its way into the storm.  So a storm system that moves from Texas to Ohio would be a needed first ingredient for a big blizzard.

We do have that storm track already established in the past month, and it’s expected to continue into winter.  The La Niña pattern we have now and expected to last through winter is notorious for storm systems curving northeastward.

In big storms, it’s usually not just one storm, but rather a merger of two storms.  This would definitely be the case for a monster blizzard.  It was the case back in 1978.  Do we have the possibility of a storm system from the northwest this winter?  We sure do.  In fact, a storm moving in out of the northwest is fairly common for any winter.  These big storms are ultimately a timing thing.  We would have to see the two storms merge at the right time.

A slow moving storm system is very important for “The Biggie.”  We would need a blocking high pressure system east of the Great Lakes.  The large high pressure that won’t budge would make the two merged storms come to a halt.  That would keep the storm in the Great Lakes for more than 24 hours.

Finally, the last ingredient is kind of like which came first- the chicken or the egg?  Arctic cold would have to move from southern Canada into the Great Lakes region.  The arctic blast would crank up the winds and change the snow to a drier, blow-around snow.  The arctic air would have to be below zero to be strong enough for wicked blowing and drifting.  It’s a debate as to whether the strong storm would pull down arctic air or the arctic air would crank up the big storm.

As far as an upper-level block just northeast of the Great Lakes, it’s not there yet.  We would need that for a slow moving storm.  But the first, most important ingredient- moisture-laden storms - is definitely a reality.

(Source: *directly quoted* https://www.mlive.com/weather/2020/12/we-have-the-ingredients-for-a-1978-style-blizzard-this-winter.html)

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— David Fair is the WEMU News Director and host of Morning Edition on WEMU.  You can contact David at 734.487.3363, on twitter @DavidFairWEMU, or email him at dfair@emich.edu