El Niño Likely, NOAA Continues Watch
While warmer sea-surface temperatures in the tropical Pacific Ocean that lead to El Niño are in place, the atmospheric signals necessary to declare an El Niño have not yet materialized. NOAA’s Climate Prediction Center forecasters say the ocean and atmospheric coupling will likely happen, predicting a 70 percent chance that an El Niño will develop in the next few months. Forecasters anticipate the intensity to be weak-to-moderate.
So what does an El Niño mean for the expected weather in the Northern Plains? Historically, there has been a much stronger correlation between El Niño and the temperatures and precipitation in the U.S. during the winter months than in the warm season. The images below show the statistical correlation between El Niño (indicated by the Nino3.4 Index) and the temperatures and precipitation across the U.S. during the cold season (November through February).
From this image, we see a positive correlation across the Dakotas, Minnesota and northern Iowa between El Niño and winter temperatures. This would indicate that there is an increased likelihood of warmer than average temperatures in the Northern Plains during a winter when an El Niño is in place.
Looking at the correlations between El Niño and cold-season precipitation above, there is a much weaker and more chaotic relationship in the Northern Plains. For southeastern South Dakota and the surrounding areas of Nebraska, Iowa, and Minnesota, there is a weak positive correlation, which would indicate increased chances of above normal winter precipitation during an El Niño. Meanwhile, areas from western South Dakota into the northern Rockies show a moderate to strong negative correlation, indicating an increased likelihood for below normal winter precipitation during an El Niño.
We must remember that El Niño is just one of numerous climate and atmospheric indices that can help us try to forecast temperatures and precipitation on a seasonal or longer time-scale, and that we have historically seen any combination of cold/warm and wet/dry seasons in past El Niño events, but it does at least give us a glimmer of hope that the region may not be in for such a long and cold winter as we saw last year.