In Tampa Bay, summer heat has officially burrowed its scorching nose into the sand, and it is showing no signs of abating.
Persistent days of heat are common as summer comes into full swing. But what has not been so consistent are the area’s afternoon thunderstorms.
Over the past week, thunderstorms have rolled through at odd times, often overnight, lighting up the midnight sky. The timing of these thunderstorms comes down to small, subtle changes in the atmosphere.
Over the next week, more hot days are expected, along with scattered showers likely influenced by drier air originating from a massive heat dome affecting much of the country.
But whether the late-night storms that may have been waking you up will continue isn’t as clear.
Here’s a breakdown of the mechanics behind our summer heat and thunderstorms so far.
Thunderstorm timing
It’s not summer in Tampa Bay without its cooling afternoon rains. And while thunderstorms have been popping up, they have rumbled through at unexpected hours.
Typically, thunderstorms are driven by a couple factors, like the location of high pressure and the collision of heat and the sea breeze.
“The land heats faster than the water, so that causes sea breezes to form, and along those sea breezes is where the thunderstorms start,” said Austen Flannery, a meteorologist for the National Weather Service’s Tampa Bay.
Thunderstorms have occurred at odd hours of the day, including Friday morning when showers doused much of Tampa Bay.
When thunderstorms occur comes down to which way, and how strongly, the wind blows.
If winds come from the east, which is what has occurred lately, storms typically form later.
But small changes in the atmosphere have led the thunderstorms to occur even later than normal, Flannery said.
Westerly winds have been weaker, causing them to get stuck near the coast. In addition, there’s been drier air, which meant thunderstorms were having a difficult time forming.
After the sun went down, the sea breeze could move inland, colliding with the sea breeze from the opposite coast at the later hour, usually after most of us had gone to bed.
“So while it was drier, it wasn’t too dry to keep thunderstorms from forming,” Flannery said.
A heat dome settles in
A sizeable area of high pressure over the United States is trapping heat and humidity, leading to extreme temperatures in the Midwest Friday and into the weekend, and in the Northeast next week.
The muggy weather is arriving from moisture blown north from the Gulf of Mexico, Jacob Asherman, a Weather Prediction Center meteorologist, told the Associated Press.
In Florida, where humid and hot are synonymous with summer, heat indices (a combination of heat and humidity) are expected to reach over or around a 100 degrees for several days early next week.
The National Weather Service’s HeatRisk map shows several days next week of “moderate” heat risk in Tampa Bay, with pockets of the region seeing a “major” risk.
Typical afternoon thunderstorms act as a natural air-conditioner in Tampa Bay, cooling off the area during the hottest parts of the day.
As the heat dome settles in, it’ll bring drier air to Florida and Tampa Bay, which will likely result in fewer storms that are more scattered.
Flannery said he expects, based on wind directions, that the area will continue to see later thunderstorms. But just how late is difficult to pin down.
“Will they be quite as late as what we saw this past week? It’s going to depend on subtle nuances day-to-day,” Flannery said.
Cooling thunderstorms?
The hottest days of summer are those when no rain falls.
While overnight storms are better than nothing, they don’t offer quite the same cooling effect as afternoon storms, Flannery said.
While rain helps to tamp down temperatures, it also adds lots of moisture, which can hold heat. Later storms also mean there’s less time to cool down.
“When it rains overnight, it does help to cool things down, but it’s kind of a double-edge sword,” Flannery said.
“You’ve already missed the window to start that cooling trend earlier, and now you’ve got all this moisture at the surface that can retain more heat.”
Over the next five days, rain chances in Tampa remain at least 50% each day while highs will be in the mid-90s, slightly above normal for this time of year.
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