GRAND RAPIDS, Mich. — April has seen temperatures well below average in West Michigan, but according to the summer forecast released by the National Weather Service, summer could be a 180 degree shift from our recent trends.
The forecast looks at multiple global weather patterns that are in place at this time, where they are forecast to go, and how these patterns impact weather locally to us in West Michigan. The two main factors identified as important to our summer weather are the El Niño Southern Oscillation (ENSO) and the Atlantic Multi-Decadal Oscillation (AMO).
The ENSO is currently in a La Niña phase and that is forecast to continue through the summer. During a La Niña pattern trade winds in the southern Pacific intensify and upwell colder water along the South American coast.
This results in something called a teleconnection. This is a phenomena where weather conditions in one part of the world impact conditions in another more distant location. In the case of La Niña we can expect to see a somewhat cooler than usual summer and possibly wetter than usual.
The impacts of ENSO are not the only controlling factor to our summer forecast, so we must also examine the state of the AMO.
The AMO only changes once every several decades and is controlled by sea surface temperature anomalies in the northern Atlantic. When these waters are warmer than normal the AMO is in a warm phase, and it is in a cold phase when these waters are cooler than normal.
The AMO is currently in a warm phase that started in the 1990s and remains ongoing at the present time.
The impacts in West Michigan of the AMO are generally a drier than average summer and a much warmer than average summer. These impacts can help negate some of the impacts of our La Niña pattern.
So, with these two competing patterns in mind, what can we expect to see this summer here in West Michigan?
When it comes to rainfall, the ENSO and the AMO are combing to more or less cancel each other out. We are looking at equal changes of near, below, or above normal precipitation through the summer months.
In terms of temperatures the AMO appears to be slightly overpowering the impacts of La Niña. With these conditions in mind, the forecast is calling for a slight chance at above average temperatures during the summer months.
In fact, warmer than average temperatures are forecast for almost the entirety of the United States.
Of course this is only an early outlook for the summer months and things can and likely will change some as we head toward the start of meteorological summer on June first.
With warmer weather on the way, make sure you stick with the 13 On Your Side Weather Team to stay up to date on the latest weather conditions all summer long!
-- Meteorologist Michael Behrens
Email me at: MBehrens@13OnYourSide.com
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