Storm Team 8 summer outlook: Temperatures, storms and Lake Michigan

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GRAND RAPIDS, Mich. (WOOD) — The coming summer should be warm and perhaps a touch on the dry side in West Michigan, bringing a lot of mostly sunny and pleasant days.

Temperatures are expected to end up 1 to 2 degrees warmer than average and I’ll guess (and it is a guess) that Grand Rapids will have 14 days that reach 90-degrees, with a maximum of 96 degrees.

WHAT HAPPENED LAST SUMMER?

A good place to start the summer forecast is to look back at the weather we had last summer. In West Michigan, all three summer months in 2020 had warmer-than-average temperatures, with the summer ending 1.8 degrees warmer than average.

However, it wasn’t extremely hot, like early July 2012. We had 17 days that reached 90 degrees last summer, but the warmest day was 94 degrees. Compare that to 2012, when we had 32 days that reached 90 degrees, nine of those days reached 95 degrees and two days topped 100 degrees. That was a hot summer.

A graph showing the number of 90-degree days in Grand Rapids since 2012.

The number of 90-degree days varies quite a bit from year-to-year. The most 90-degree days in Grand Rapids since 1964 has been 37 in 1988. The least was zero in 2014 and, before that, 1951.

TEMPERATURE FACTORS

Another key factor in the summer forecast is ocean water temperatures. The below map shows sea surface temperature differences from the average. Where the map is blue, the water is cooler than average and where the map is yellow, orange and red, the water temperature is warmer than average.

Sea surface water temperature anomaly map.

Meteorologists look at the water temperatures in the central and eastern Pacific along the equator. You can see the water there is now cooler than average. We call this pattern La Nina. This La Nina pattern started early last summer and has stuck around.

I suspect this La Nina is going to trend back to neutral (called La Nada) during the early summer. So I looked back through the years to find when we had a second-year La Nina trending toward neutral. These are sometimes called analog years. If you look at these years (I chose six years that fit the pattern we have now), it’s more common that you will have a warmer-than-average summer than a cooler-than-average summer.

One other thing to add: With La Nina continuing, this should be another very active Atlantic hurricane season. Last year, we had 30 named storms in the Atlantic, Caribbean and Gulf of Mexico, 13 hurricanes and six major hurricanes. Five storms came onshore just in Louisiana. On the other side, we had a record fewest tropical storms in the western Pacific.

Five named storms in the Atlantic at the same time in 2020.

If you really want to do some meteorological exploring, check out the AMO — the Atlantic Multidecadal Oscillation. This oscillation moved into the warm phase in the mid-1990s and I think this is also an important factor in our general weather.

When the AMO is positive, there are more warm winters in West Michigan and when it is negative (as it was in the 1960s and 1970s), there are more colder-than-average winters. When the AMO was negative, we had the three successive very cold and snowy winters from 1976 to 1979.

Right now, the AMO remains positive, which is a warm signal.

RAINFALL

Rainfall last summer totaled 10.19 inches in Grand Rapids, .95 inches below average. We had 91% of average rainfall, or pretty close to average. We had a little above-average rainfall in July and a little below-average rainfall in June and August. Keep in mind that summer convective rainfall can be quite spotty. You can have a deluge in Rockford while Cedar Springs gets a sprinkle.

Above is the drought monitor. It has not factored in the rain we got this past weekend, which measured 0.51 inches in Battle Creek to 1.75 inches in Kent City; the Florida peninsula also had a good soaking.

Note that soil moisture is good at this time across most of the Corn Belt.

There is significant drought across much of the West, which is not uncommon. Much of agriculture in the West is irrigated and less dependent on regular summer rainfall.

Often, heat ridges set up where there is dry soil. In those areas, a higher percentage of the sun’s energy can be used to heat the air rather than evaporate water. I expect the usual Bermuda High in the Atlantic and another ridge that sets up from time to time this summer over the Rockies and western Plains. I think it will be a hot, dry summer there in the Plains states.

North American Snow and Ice Cover

There is relatively little snow in the U.S. and Southern Canada right now, but there is still a solid snow cover across northern and central Canada. Hudson Bay is frozen solid, as it nearly always is in mid-April. That can be a source of cool air into early summer. June 1, 2012, was the Friday start of Festival of the Arts in Grand Rapids and there was a cold rain most of the day and a chilly wind coming down from Hudson Bay. The high temperature that day was 54 degrees. It turned out to be just a speed bump in what was otherwise a very warm spring and summer.

In “summery,” I’m forecasting this summer will be a little warmer and a little drier than average with a little above-average sunshine.

—Storm Team 8 chief meteorologist Bill Steffen

SEVERE WEATHER OUTLOOK

Severe weather — defined in terms of tornadoes, 1-inch diameter hail or larger and wind gusts of 58 mph or greater — has seen a general downward trend this past decade.

Since 2000, an average year in Michigan would bring 483 reports of severe weather. This past decade, we’ve received an average of 365 reports which is down 24%. The last above average year was in 2011 with 582.

2011 represented a year with a strong La Nina. I mention this because La Nina years tend to have more severe weather across the Central U.S.

We are currently in a weak La Nina, with cooler waters persisting across the eastern Pacific equatorial region:

La Nina weather patterns during the spring have been shown to increase severe weather in the Central U.S.

The question is whether that will translate north into the Great Lakes.

Though the next couple of weeks appear free of severe weather, the April through June outlook from the Climate Prediction Center indicates a wetter pattern.

The core of upper-level winds we call the jet stream migrates north during the summer and weakens. It still can be the focus for the development for summer thunderstorms.

During a La Nina summer pattern, a large ridge typically develops along the West Coast. This normally forces the jet stream to dip south across the Northern Plains and Great Lakes. As it does, it has a better chance of intersecting warm and humid Gulf moisture air, resulting in the development of thunderstorms. The stronger jet stream winds can add additional energy to the thunderstorms increasing the chance of them becoming severe.

What it boils down to is how many thunderstorms there will be and how intense they will get. Since the current state of the La Nina is forecast to remain weak, I don’t think its influence will be exceptionally strong.

Keep in mind, though, that the past several years have shown below-average numbers, with last year coming in with a total of 389 storms. I do expect an uptick closer to average this summer, which would be around 480 reports statewide.

I would also expect a better chance of straight-line wind events we call derechos. We came very close to getting one Aug. 10, 2020, after a storm pummeled Iowa and northern Illinois. Fortunately, it weakened just as it crossed Lake Michigan.

I would expect close to possibly slightly above-average tornado count.

Thunderstorms and severe weather are inevitable across Michigan. With an average of 35 to 40 thunderstorms per year, we always have to be on the lookout.

You can always count on Storm Team 8 to help guide you and your family when severe weather threatens.

—Storm Team 8 meteorologist Matt Kirkwood

LAKE MICHIGAN WATER LEVELS

The high water levels on Lake Michigan have led to major concerns over the past few years. Record low water levels were recorded in 2013, then several years with above-average precipitation across the Great Lakes basin led to record high water levels in 2020.

Oval Beach in Saugatuck on July 27, 2021. (Luke Stier/WOOD TV8)

Though water levels are no longer in record-breaking territory, they will remain high this summer.

According to Deanna Apps, a physical scientist with the Detroit District of the U.S Army Corps of Engineers, the water levels on Lake Michigan are about 11 inches lower than last year.

There has been lower-than-average precipitation across the basin in recent months, which reduced the runoff. Consequently, the seasonal decline in water levels has been greater than average this year.

The water levels usually begin to rise in the late spring and the rise continues into the summer. Late summer or early fall is when water levels typically begin to decline. This means that the current water levels on Lake Michigan are likely at their lowest for this year, and the seasonal rise will begin soon.

2019 set the stage for the record high water levels in 2020. Apps explained that 2019 was a wet year with a large spring rise and an extremely small seasonal decline, so we entered 2020 with very high water levels. Monthly water level records were broken eight months in a row in 2020, from January through August.

Thankfully, water levels are not forecast to break any records this summer.

The U.S. Army Corps of Engineers Detroit District issues a 6-month water level forecast each month. The current outlook goes through September. It suggests water levels will stay below the levels last year by about a foot, but they will still be high. Apps expects the water levels to stay around 1.5 to 2 feet above average.

(Courtesy the U.S. Army Corps of Engineers Detroit District)

It’s hard to say if a rapid swing in water levels like the one between 2013 and 2020 will happen again. According to Apps, water levels are hugely dependent on meteorological conditions. In the same way we can’t forecast the weather years in advance, it’s hard to know where water levels will be years in advance.

Even though water levels will be lower this year, they will still be significantly higher than average. We’ll continue to monitor the levels and their impact on the lakeshore.

Tunnel Park on Lake Michigan in April 2021. (Nick Ponton/WOOD TV8)

—Storm Team 8 meteorologist Emily Schuitema

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