Not a Typical La Nina Winter

Mar 01, 2021

By Pam Knox

Today is the last day of meteorological winter, and in spite of being in a La Nina this year, it has not felt nearly as warm and dry as we usually expect from a LN winter due to the impacts of the Sudden Stratospheric Warming (SSW) which pushed the storm track south into our region, bringing clouds, rain, and cooler temperatures than expected. Don’t blame the climatologists, since forecasts are done on a statistical basis and in the majority of years an LN winter should look a lot more typical than it did this year. We are trying to improve these forecasts over time, but SSW events are generally not predictable and can only be reacted to once they start. And even then, the impacts of each SSW are not the same so we can’t say with certainty how any of these events will affect us once they start.

Here are the preliminary maps for February 2021 and December 2020 through February 2021 temperature and precipitation departures. Note that areas that were not right along the storm track were generally warmer and drier than usual, but within the storm track, cloudy temperatures kept daytime temperatures cooler than normal, although nights were warmer than usual almost everywhere. The excessive rainfall has been a problem for farmers trying to get into their fields, but the next few weeks look drier and warmer, which will improve things, I hope.

All these maps are from https://hprcc.unl.edu/maps.php?map=ACISClimateMaps.

Source : uga.edu

Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.