NOAA updates its seasonal forecast once a month. The latest update for summer was released yesterday. It’s a slight twist to Michigan’s summer forecast.
Just below is a comparison of the previous month’s forecast for June, July, and August (right) with the June, July, and August forecast given on May 18 (left).
NOAA’s long-range forecasters have downplayed the likelihood of a warmer-than-normal summer in Michigan. In the April forecast, all of Michigan has a 40% chance of warmer-than-normal temperatures in June, July, and August. In the latest forecast from yesterday, a warmer summer is likely. normal has dropped to 33%.
It’s not a huge change, but it does show a trend toward reducing thinking about a really warm summer.
Remember that forecasting is done using all computer models capable of predicting that time period in advance. There is also an underlying climate trend that is included in the forecast. Of course, the current baseline temperature trend is warmer-than-normal temperatures.
So what has changed in a month to ease the confidence of a warm summer? The rapidly developing El Niño is the main reason for the slightly colder forecast. El Niño is likely to develop over the next two months. With El Niño’s warmer waters emerging, El Niño could turn strong this summer.
Looking back at past El Niño summers, which tended to be cooler than normal summer conditions in the Great Lakes region. Of course, this cooler seasonal effect from El Niño is somewhat balanced by global warming trends.
Another study by Bill Marino, a retired meteorologist with the National Weather Service, favors a slightly cooler idea for the summer. He noticed a slight decrease in the number of days with 90 degrees in western Michigan during the El Nino summer. He found that the average temperature did not get much cooler, but the hottest days did decrease.
Johnna Infanti at NOAA’s Climate Prediction Center released this latest summer forecast. Johnna told me another reason summers aren’t as warm anymore is the water temperature in the Great Lakes today. Water temperature is slightly cooler than normal to about normal. The theory here is that heat coming from the west and southwest will be cooled somewhat by the waters of the Great Lakes, at least in early summer.
It could be stacked up to be a “normal summer” in Michigan, if there was such a thing.