La Niña Winter Ends: What usually follows in the spring?
SAGINAW, Mich. (WNEM) - The winter season has come and gone, at least from the climatological perspective, and meteorological spring began on March 1st. We already crunched the numbers on the winter season in our Winter 2023 Winter Recap, so be sure to check that out if you haven’t already.
But now it’s time to look forward! Transition seasons are tough to forecast in Michigan while they’re happening, let alone trying to forecast the entire season. However, looking back historically following previous La Niña winters and seeing what followed in the spring may provide some clues.
Since 1950, we’ve had 25 La Niña winters on record. These La Niña events are classified into Strong, Moderate, and Weak La Niñas. The complete classification can be found in the image from NOAA below.
For the winter of 2022-2023, we were under a Moderate La Niña, which was our third Moderate La Niña in a row for the winter season.
Mid-Michigan History With All La Niñas (All Strengths)
To get a general idea of how the season leaned with temperature and precipitation, all La Niña years were included initially regardless of strength.
- Author Note: Although La Niña and El Niño are two important tools when it comes to seasonal forecasting, they’re not the only determing factor. We have had both above and below average years when it comes to precipitation and temperature with both climate signals.
When it comes to temperature, La Niña springs tend to lean cooler than average in the TV5 viewing area. 16 out of the 25 years featured cooler or near normal temperatures, with only 9 La Niña springs ending up on the warmer side of average.
For preciptiation, the connection was a little bit more mixed, with 15 years near normal, 5 year above, and 5 years below average. With results like that, there’s not much of a lean either way, with generally average conditions most years historically.
Mid-Michigan History With Moderate La Niñas (6 Events)
Although we have a general idea of the way things lean when looking at all La Niña years, it seems to be more productive to see if there are any connections we can take away, statistically speaking, from Moderate La Niñas.
Moderate La Niña winters, like all La Niñas grouped together, leaned more toward the cooler side of average. There were two instances out of six, that ended up above average, with the other 4 (66%) being cooler than normal or near normal. This is a small sample size of course.
Precipitation also followed the same trend as all La Niña events, with no clear lean toward above or below average precipitation. As a whole, Moderate La Niñas had mixed results, with three above average seasons, two below average seasons, and one near normal season.
Snowfall & Freeze Statistics (Based on Saginaw)
We couldn’t write this article without giving any historical perspective on snowfall or cold temperatures. However, for simplicity, we used Saginaw as a centralized location in the TV5 viewing area.
When it comes to the last measurable snow of the season (0.10″ or more), we found that in the spring following all La Niña winters, the last measurable snow occurred after March 31st 60% of the time. When it comes to Moderate La Niñas, that percentage of the last snowfall occurring after March 31st jumps to 83% of the time.
For those curious, a strong La Niña has the last measurable snow after March 31st 71% of the time, with weak La Niñas coming in at a 66% of the time.
The average last occurrance for measurable snow is roughly April 6th.
For the last 32 degree temperature of the season, the result may actually surprise you considering the spring season tends to lean cooler than average.
When looking at all La Niñas, the last freezing temperature of the season occurs before May 1st around 66% of the time, For Moderate La Niña events, 83% of the time it occurs before May 1st.
With the cooler than average ocean waters of La Niñas having more of a temperature connection on the spring season more than precipitation, it doesn’t seem surprising that a Strong La Niña has the last 32 degree temperature occur after May 1st around 57% of the time.
Interesting 2000-Present Trend
It was discovered in the research that all spring seasons that followed La Niña winters from 2000 onward, leaned near or above average when it comes to temperature. This was most pronounced in Weak La Niña years, with the least influence in Strong La Niña years, where those seasons leaned near normal with temperature.
With precipitation, it still wasn’t a strong lean, but from 2000 onward, spring seasons that followed all La Niña winters leaned more near and above average, rather than a mix. Out of ten events, only one season checked in with below-average precipitation.
When looking at this information as a whole, there seems to be a trend historically speaking. Temperatures in the spring season, following a La Niña winter seem to be near or cooler than average most of the time, with precipitation having no clear signal, leaning close to the middle with near normal precipitation.
Snowfall that’s measurable occurring after March 31st seems to be the most likely scenario, and some of our long term models seem to support that idea. However, we always want to clarify that models are just tools, and aren’t always right, especially that far out in time.
The final freeze of the season tends to lean before May 1st in the Saginaw area, despite the spring season as a whole leaning near or cooler than average more often that not.
Although one could theorize climate change could be playing a factor from 2000 onward in our springs that follow La Niña winters, it’s tough to come to a conclusion with only ten instances. But it’s definitely a noteworthy observation worth monitoring.
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