Summertime weather: Why there are storms forecast for every afternoon this week

Summertime weather: Why there are storms forecast for every afternoon this week

By Brad Klein

July 13, 2021

With scattered showers and thunderstorms developing most afternoons lately, WLVR’s Brad Klein speaks with Dean Iovino, a meteorologist at the National Weather Service in Mt. Holly, N.J., about the typical pattern of summer weather affecting the Lehigh Valley and why the hottest days of the year in the Valley tend to follow the longest day of sunlight by as much as a month.

Brad Klein

“I’m joined now by Dean Iovino, a meteorologist at the National Weather Service Center in Mt. Holly, N.J. Are you with me, Dean?”

Dean Iovino

“Yes, I am Brad. Good morning. 

Klein

“Good morning. So the forecast has become pretty familiar to our listeners. Why is that sort of the typical summer pattern here?” 

Iovino

“What often happens in our area is that we get cold fronts, not really cold, but just a little bit cooler air pushing down from the north during the summertime. But it doesn’t have a very strong push behind it so the cold front tends to get hung up across the northeastern states this time of year rather than pushing all the way through as they often do during the autumn, winter and spring. 

“So the fronts get hung up and they tend to trigger these hit or miss showers and thunderstorms that are generally focused in the afternoon and evening hours during this time of year. So yes, as you mentioned, we’re kind of stuck in this pattern for the next several days with Thursday being the only day where we might get through the entire day in our region without any precipitation.” 

Klein

“Now, we’ve had flash flood warnings. Well, the Lehigh Valley was part of the flash flood warning yesterday and I guess that’s related to that pattern of sudden thunderstorms.” 

Iovino

“Right. The main problem was yesterday as we were anticipating that the scattered showers and thunderstorms would develop but there wasn’t much wind to push them around. So if they did develop, they would park over the same area and it would rain heavily for several hours which, unfortunately, was the case for lower Bucks County, which received anywhere from 6 to 10 inches of rain yesterday with some fairly significant flooding occurring at that time.” 

Klein

“That did result in the need for some moving water rescues and things, as I saw on social media.” 

Iovino

“Right. It’s highly unusual but it does happen from time to time, so it was a lot of rain in a very short amount of time.”

Klein

“It’s a good lesson to take these weather forecasts seriously, even if they do sound a little repetitive sometimes in the summer months.

“While I’ve got you on the line, I was also sort of intrigued to see that the hottest days of the year here in the Lehigh Valley are potentially ahead of us, or at least on average there sometime in mid- to late July, given that the longest day of the year was about three weeks ago with the summer solstice. So as long as I’ve got a meteorologist on the line, what’s up with that?” 

Iovino

“Well, the reason for that lag is, as we know, when we go through the spring months in the northern hemisphere, with each passing day the number of minutes of daylight increases a bit and the sun angle increases as well. So that results in a gradual heating of the northern hemisphere. But once we get to June 21, that heating process doesn’t turn on a dime. In other words, even though once we get past June 21, the days get slightly shorter daylight-wise and the sun angle lowers just a bit each day. It really doesn’t have an impact on turning things around for another 3 to 4 weeks or so.” 

Klein

“And in fact, those long days continue to sort of warm us up right on average. And that’s why that lag to the hottest day of the year on average.” 

Iovino

“Right . You don’t get enough of a loss of sun angle or daylight initially to really have an impact on slowing that heating process dance. And you’ll see the same thing on the other side of the year even though the winter solstice is around Dec. 22. The coldest time really isn’t until closer to Jan. 20.” 

Klein

“I’m happy to put in a plug for the Mount Holly New Jersey National Weather Service twitter feed which I find always interesting and adds depth and even sometimes some levity to the forecasts. I think you guys do a great job with that.” 

Iovino

“Thank you. We appreciate the kind words.” 

Klein

“That’s Dean Iovino, a meteorologist at the National Weather Service in Mt. Holly, N.J. Thanks again for being with us.” 

Iovino

“My pleasure. Have a good day.”

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