NOAA Climate Prediction Center forecasters say El Niño will impact winter for the first time in four years, but what does that mean for the Chicago area and winter weather?
Winter El Niños typically cause big changes in forecasts in the Chicago area, but forecasters warn that “no two El Niños are the same.”
“Strong El Niños do not necessarily have strong local impacts, and the probability of associated climate anomalies is often lower than the probability of El Niño itself,” the NWS reports.
Here’s what you can expect.
What is El Niño?
According to Dr. Jim Angell, Illinois state climatologist, El Niño is a period of unusually high sea surface temperatures in the Pacific Ocean, especially near the equator. It’s the opposite of La Niña.
“These (increased water temperatures) change weather patterns in the Pacific Ocean, which in turn changes weather patterns in many other parts of the world,” Angell said.
“Under normal conditions in the Pacific, trade winds blow westward along the equator, transporting warm water from South America toward Asia,” according to the NWS. But thanks to a process called ‘upwelling’, cold water rises from the ocean floor to replace the warm water. But when El Niño occurs, the trade winds weaken, pushing warm water back east.
How does El Niño affect weather conditions?
Typically, when El Niño occurs, parts of the northern U.S. and Canada are drier and warmer than normal, but the Gulf Coast and Southeast can experience wetter than normal conditions, increasing the risk of flooding.
What about the Chicago area?
Last winter brought an astonishing amount of rain and above-average temperatures to the Chicago area, and the latest forecast suggests the same could happen.
The effects of El Niño events in Illinois typically vary depending on their size, strength and duration, Angell said.
“As a result, impacts may vary from event to event. Additionally, there may be other factors that influence Illinois weather during these events,” Angell said.
In general, impacts may include:
- Summers tend to be slightly cooler and humid than average
- Waterfalls tend to be wetter and cooler than average
- Winters tend to be warm and dry
- Spring tends to be drier than average
- Snowfall tends to be below normal
- Heating degree days tend to be below average, resulting in lower heating costs.
What are the latest predictions?
According to NOAA’s seasonal temperature outlook released Thursday, forecasters say most of Illinois and Indiana are “leaning toward” a warmer-than-normal winter. Confidence has increased in areas near Lake Michigan, where forecasters say there is a “high probability” of higher-than-normal temperatures throughout the winter.
Most of the Midwest and northern United States will experience above normal temperatures, and the Pacific Northwest and New England will most certainly see warm temperatures.
In terms of precipitation, much of Illinois is expected to see near-normal snowfall this winter, but most of Indiana and far eastern Illinois are expected to see below-normal winter precipitation. It has been.
The southern United States is expected to experience wetter than normal conditions, similar to previous El Niño events.