Rain, storms break through dry August spell

Mark Hicks
The Detroit News

This month, there have been five days where more than one-tenth of an inch of rain has been recorded at Detroit Metro Airport.

Rain was reported at the airport in Romulus over the past week on Thursday, Saturday and Sunday, as well as traces on Aug. 12 and 13, National Weather Service data said. However, over the 48 hours comprising Aug. 12-13, strong storms dumped as much as 3-6 inches of rain elsewhere in the region, sparking flooding and road closures.

The numbers reveal a prevailing trend as the dog days of summer 2019 envelop southeast Michigan forecasters say: drier air plus fewer chances for severe weather sparking hit-or-miss downpours.

Storm clouds pass over the Detroit River near Bishop Park in Wyandotte on Aug. 12.

“It’s the nature of the beast with convection,” said Steven Freitag, a meteorologist with the National Weather Service station in White Lake Township. “This is just normal variability.”

Normal, maybe, but for those getting hit by recurring rains and flooding, it can be draining. Storms on Sunday didn't produce flash flood or flood warnings, but the threat of bad weather continued into the night, with the weather service sending out a severe weather warning of lightning, hail and winds up to 60 mph. for parts of the region.

At least an inch of rain fell in Flat Rock, which reported downed trees and power lines. Earlier storms Sunday left about 39,000 people without power: 30,000 at DTE Energy and 5,500. By Monday morning, some 13,000 customers with DTE Energy remained without power. 

Between June 1 and Friday — before Sunday rain total was tallied — only 6.25 inches of rain had been recorded at Detroit Metro Airport, while the average amount for the same time frame is 8.53, the weather service reported. Sunday's rains brought 0.13 inches of rain in a first round of storms. 

Agency data show this month has so far mirrored conditions in July, which was marked by less precipitation as well as slightly warmer temperatures.

Temperatures during August, which is typically the region’s second-hottest month, have been about 2 degrees warmer than normal, the weather said. Highs each day have hovered in the 80s, while lows did not dip below 59, weather service data shows.

Meanwhile, through Friday, Detroit Metro Airport had recorded 0.76 inches of rain. That was nearly an inch below normal for the first half of August, the weather service said.

The average total for the month is 3 inches, the data shows. The top 20 driest Augusts all notched 1.2 inches or less, according to the weather service.

What’s behind the dry spell?

“We haven’t had too many days where the humidity is high,” Freitag said. “We have been getting more dry Canadian air sweeping into the Midwest. We haven’t generated the massive thunderstorm complexes that spread east. That is how we get some of our biggest storm producers in the summertime.”

The fewer storms that have descended on the area can also drop widely varying rainfall amounts, depending on factors such as front boundaries and the strength of isolated cells, Freitag said. "It’s just typical summer patterns."

The August 2019 rainfall totals are nowhere near the lowest the weather service has registered for the month in more than a century of record-keeping. That distinction went to August 1894, when only 0.16 inches fell. The highest was 8.33 in 1926.

Still, the scant rain has had some impact.

The U.S. Drought Monitor report released last week showed parts of southeast Michigan and the Thumb, including Macomb, Oakland, St. Clair, Lapeer and Genesee counties, were “abnormally dry.”

There's a chance of thunderstorms Monday and Tuesday as the mercury rises near 90.

“I’m pretty confident we’ll see another inch between now and the end of the month,” Freitag said Friday.