We’ve been expecting a La Niña to form and influence our winter weather in Michigan and across the U.S. There are some significant changes to the development of La Niña compared to forecasts over the past few months.
Remember- La Niña is an ocean condition where the Pacific Ocean water surface temperatures along the Equator turn cooler than normal. It is an ocean condition that is the opposite of El Niño, when equatorial Pacific waters turn warmer than normal.
Graphs show the surface water temperature anomalies at various sectors of the La Niña region. Note the trend toward slowly cooling waters.NOAA
Also I want to point out that ocean water temperature forecasts are not always spot-on like a daily weather forecast. We’ve had models to forecast ocean temperatures for several decades. When the temperature forecast of an ocean is off, it’s not by a day or two. It’s off by a month or two. It takes a long time for ocean temperatures to change.
That is the current situation. La Niña was forecasted to develop this summer, but has yet to develop. The latest discussion from NOAA’s El Niño/La Niña forecasters now says a La Niña should still develop. They give La Niña a 70 percent chance of now developing between October and December. NOAA still expects La Niña to be occurring during our winter.
What’s important however are a few new expectations. The La Niña is now expected to only be a weak La Niña. The previous forecast called for a moderate strength La Niña. The second update is also important. The La Niña is expected to be short-lived and maybe last only until around March.
All of the model forecasts of surface water temperature anomalies in the La Niña region. Dark purple line is the average forecast of all the models.NOAA
The change in strength is important because stronger La Niñas and El Niños have more influence on Michigan’s winter weather and the entire U.S. winter weather. A weak La Niña won’t have much influence on our winter weather here in Michigan. The current winter temperature forecast made mid-September started to incorporate the idea of a weak, short-lived La Niña. As a result the temperature forecast was tweaked from around normal temperatures to slightly warmer than normal temperatures.
While even a strong La Niña doesn’t even have a big influence on winter temperatures here in Michigan, a strong La Niña does seem to create a strong signal toward wetter than normal conditions across the Ohio Valley and into southern Lower Michigan. So again- the weaker La Niña would have a slight reduction in the current wetter than normal winter forecast.
The short duration of the La Niña is also important. Much of the weather effects here in Michigan due to a La Niña are evident in the last part of winter and early spring. Without La Niña after March we should say there will be no influence of La Niña in our early spring.
I want to caution you on your idea of a winter forecast. La Niña and El Niño are just one piece of the long-range forecast puzzle. If either of these conditions are strong they give us a good chance at an accurate long-range winter forecast. But there are a lot of other pieces to the winter weather puzzle. Just because the weaker La Niña has caused a slight warming to the winter forecast, other unknown factors can still produce plenty of winter weather.
The main important fact here is the winter may have just trended slightly warmer and slightly drier than the current winter forecast.
We will still have winter here in Michigan, with snow and wind and cold.
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Publish date : 2024-09-25 05:28:00
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