GRAND RAPIDS, Mich. (WOOD) — Global signals are indicating West Michigan will be most likely to see a wetter than average winter this season.
But with only a moderate La Nina at play and a third year in a row of La Nina conditions, certainty on some of the secondary variables in this winter’s forecast are a touch lower than usual.
No two winters are exactly the same, but there are signs and tools forecasters use to get an idea of how a season will play out. Just as with a short-term forecast, some can be quite certain while others will be inherently trickier. Below, see a breakdown of those signs and tools:
TRIPLE-DIP LA NINA
Oceans cover 70% of the planet’s surface and play a significant role in Earth’s climate and weather system. For years, meteorologists have intensely researched the impact water temperature departures from normal in the equatorial pacific have on the upcoming winter.
When water along the equator to the west of South America is colder than average due to stronger than usual trade winds, we often see an impact in the northern hemisphere jet stream. This means the water off the coast of South America can help determine what we see here.
For the third year in a row, colder than average conditions have set up in this area of the Pacific Ocean. Researchers call this a La Nina phase. While La Nina conditions aren’t rare, there are a lot of different kinds of them and rarely do La Nina conditions return for three years in a row. This is the first time this century a La Nina is forecast to return.
Because a third-year La Nina is so rare, there are very few historical matches to pull winter data from. That being said, a moderate La Nina forecast to weaken in the spring typically still leads to a wetter than average winter season for us in West Michigan.
Early-season Siberian snow cover is another global indicator that has a pretty decent correlation to the winters here in West Michigan. While no forecast indicator controls the winter season completely, it is another ingredient in the mix. Typically when we see early-season Siberian snow cover and more than usual in October, there is a higher likelihood of a colder than average overall winter.
This season, we are getting muddled signals from Siberia, which is one of the reasons forecast certainty for this upcoming year are not exceptionally high. There are far fewer years with a similar early season Siberian snowpack signal to compare this to, but it is still helpful data for the seasonal computer models to ingest and process.
JET STREAM LOCATION
One of the biggest players in the winter forecast in West Michigan is our jet stream. The jet stream is a ribbon of fast-moving air that exists around 5 to 7 miles above Earth’s surface. The jet stream location changes almost constantly and the differences affect our weather greatly. The jet stream, in simplest terms, traps cold air on its northern side. So if the jet stream dips south of Michigan, it will allow cold to seep in here.
The jet stream is also responsible for steering storm systems our way. In the winters of 2019-2020 and 2020-2021, the jet stream only delivered one cold month for each winter season. This led to very low lake-effect snow totals and near-average system snow totals. The end result was two winters with very low snow accumulations for our area.
In addition to a La Nina and Siberian snow cover, things like the water temperature departure from normal in the Gulf of Alaska, polar vortex strength and global patterns like the Madden-Julian Oscillation can all also change the jet stream constantly in Michigan during the winter. Unlike a La Nina or Siberian snow cover, things like the water temperatures in the Gulf of Alaska and the polar vortex can only be forecast effectively about three weeks out at maximum. So while these factors can have a big impact, they can only be roughly accounted for in a winter outlook.
OVERALL WEST MICHIGAN WINTER OUTLOOK
This winter in West Michigan is forecast to be wetter than average with near-normal snowfall totals due to a moderate La Nina. We will likely see conditions flip-flopping from month to month as some of the secondary factors listed in our discussion steal the show at times. At least one icing event is expected this season. Wintery weather is not expected to linger long into spring.
Since this will be a year with a lot of variability, Storm Team 8 will be active daily to keep you updated on the big impacts (or lack thereof).
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