The El Niño swing to La Niña is now fully in effect, with the official end of El Niño declared by NOAA today. But what does this mean for weather impacts in Tornado Alley and beyond?

In our seasonal forecast, we noted that swinging El Niños (those rapidly weakening to La Niña) had a high correlation with very active Spring tornado seasons. We saw that play out once again this year. Looking ahead, there are a few trends that stick out amongst top analog years:

  • Tornadoes are concentrated in an axis from the Central High Plains to Minnesota, including the Dakotas and Nebraska throughout the summer months. Numbers are at or slightly above average for this time of year.
  • The jet tends to remain active, which fits with the above.
  • Summers can be rather hot/dry in the Southern Plains. 
  • Monsoon seasons are on the dry side in the Southwest.

Another thing the NOAA forecast did point out is that the La Niña pattern may not emerge as quickly as once thought. There has been a lot of expectation for this hurricane season to be incredibly active — but this is the type of thing that could cause a lot of forecasts to bust. Or it could just mean the season takes a bit longer to get going as the upper air pattern unfavorable for hurricanes takes slightly longer to clear. We won’t know that fully until we know (ha).

Moving forward, if La Niña does establish there are two things that are pretty typical:

  • The axis of tornado seasons tend to be quite east AND active (Southeast/Mid-South) with a secondary axis on the High Plains late.
  • Drought will set in over large portions of the middle/SW parts of the country.

But it’s early, so let’s not get ahead of ourselves on speculation. We’ll be keeping an eye on it, but don’t expect the severe weather events to slow too much during the summer, expect them to remain north where they’ve been for a couple of weeks already.