NOAA released a statement on Thursday, October 14, 2021, stating “a La Nina has developed and will extend through the second winter in a row” calling it a “double-dip”.
[ >>NOAA 2021 La Niña Pattern Explained ]
La Niña is an natural ocean-atmospheric phenomenon that is caused by the upwelling of ocean waters across the central and eastern Pacific Ocean near the equator creating cooler than normal sea surface temperatures in this region. The opposite of this is an El Niño, which features warmer than normal sea surface temperatures.
During La Niña winters, the Polar Jet Stream becomes ridged across the Pacific Northwest, creating a trough through the north-central United States.
“Our scientists have been tracking the potential development of a La Nina since this summer, and it was a factor in the above-normal hurricane season forecast, which we have seen unfold,” said Mike Halpert, deputy director of NOAA’s Climate Prediction Center.
According to NOAA, this La Nina pattern is expected to last through Spring 2022.
Particularly across the Miami Valley, a wetter a than normal winter is to be expected, but whether it’s snow or rain is often decided by other global patterns like the Arctic Oscillation.
Previous La Niña occurred during the winter of 2020-2021 and 2017-2018.