It’s not every summer that the remnants of three tropical storms pass over the Poconos, dumping more than a foot of rain on Stroudsburg in just over two weeks.
It’s also not every summer that wildfires thousands of miles away contribute to poor air quality and markedly hazy skies in the eastern United States.
But as Earth’s air and water warms up, can we expect to see these events and other weather phenomena starting in the summer of 2021 more often?
Here’s a look at how climate change is impacting the weather conditions the Poconos have experienced this summer.
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Tropical storms and rain
A series of three tropical storms – Fred, Henri and Ida – meant Stroudsburg had its third wettest August on record, and September also saw a wet start.
Tropical cyclones are, on average, increasingly intense due to higher air and water temperatures.
Not all of the ingredients of a tropical storm are affected by climate change – a slight wind shear is needed, for example – “but there is more fuel,” said Ben Gelber, an Ohio meteorologist who grew up in the Poconos. “In other words, water temperatures are on average 1 to 2 degrees warmer, and that’s a lot of extra moisture or water vapor getting into the atmosphere.”
Large storms move more slowly, so the combined effect is that tropical storms have more water to release and areas can receive rain for a longer period of time. This means that “more areas are sensitive to flash floods, both in terms of rainfall intensity and duration,” Gelber said.
“Flooding is currently the most risky danger Pennsylvania faces, and the risk of flooding is expected to increase,” according to a 2021 Pennsylvania Department of Environmental Protection report on the impacts of climate change.
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The Stroudsburg / East Stroudsburg region has already seen an increase in average annual precipitation since the mid-20th century, Gelber said. The average over the 30-year period from 1931 to 1960 was about 48 inches per year, and that figure rose to 53.5 inches from 1991 to 2020.
Average temperatures in June and August were about 3 degrees above average, while July was “about average,” Gelber said.
The Poconos have not broken any records for high temperatures this summer; closest to the area was a tie or near-tie with Stroudsburg’s maximum mark of 96 degrees on June 30. (The official maximum for that date this year fell to 95.3 degrees in National Weather Service data; two other unofficial but reliable weather stations reached 96, Gelber said.)
There weren’t an unusual number of days above 90 degrees either – so what kept those averages going in June and August?
“We tend to think of hot summers as a set of 90 degree days, which can be the case, but in this case the average temperatures are supported by the higher humidity and persistent cloud cover, which keeps the temperatures down. warmer nighttime temperatures. said Gelber.
Three times in the past few years, “a new record minimum temperature” has been set, Gelber said. In other words, the average summer nights don’t get colder as much as they used to.
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Stroudsburg’s record monthly average was 63.9 degrees, set in July 1949 and tied in July 2012. This average hit new highs in August 2018, July 2019 and most recently in July 2020, when it hit 64 , 8 degrees.
Breaking that record three times in three years “is subtle but very important information,” said Gelber. “When you talk about climate change, we’re looking for a cluster of unusual events, not just one event. “
Rather than having a hot summer, Stroudsburg has repeatedly seen its low temperatures rise. Warmer nights are “consistent with the physics” of climate change, he explained.
“Warmer air has a greater capacity to store water vapor,” Gelber said. More humidity means more clouds, and “the clouds act as a blanket to retain heat.”
The DEP report, after noting the expected increase in daytime temperatures of 90 degrees and above, added that “the Commonwealth could also see more days when nighttime temperatures do not drop below 68 ° F, a key threshold for the relief of infrastructure and human health. “
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The most devastating effects of forest fires – deaths, destroyed homes and buildings, burnt area – occur where the fires occur. But the Poconos saw the far-reaching effects of a bad wildfire season this summer, when smoke moved far enough to turn the sky a hazy yellowish gray.
The problem with climate change isn’t that the haze has reached Pennsylvania; it just requires the right jet stream model. It’s that wildfire seasons are getting longer and more active, Gelber said.
While fires are “a natural part of many ecosystems in the Southwest,” according to the most recent national climate assessment prepared by the National Oceanic and Atmospheric Administration and other agencies, the number of acres burned in recent years has increased due to climate change.
“Climate change has led to an increase in forest fires, in particular drying out forests and making them more likely to burn,” according to the report. “Specifically, rising temperatures have intensified drought in California, contributed to drought in the Colorado River Basin, reduced the snowpack and caused spring temperatures earlier in the year.”
Smoke from forest fires includes particles that create air quality problems and exacerbate existing pollution.
The DEP published Code Orange action days on air quality on July 20 and 21. The alerts did not extend north to the Poconos, but did include neighboring counties of Lehigh and Northampton.
Orange days on the United States Environmental Protection Agency’s Air Quality Index means “unhealthy pollution levels for sensitive groups of people” such as children, the elderly and people with respiratory problems.
It is rare for these alerts to be issued by DEP for smoke from distant fires, the most recent orange days or greater for this reason having occurred 19 years ago.
“The DEP has already launched days of action on air quality for (fine particles) in July 2002 due to the smoke from forest fires in Quebec,” said DEP spokesperson Jamar Thrasher. “The levels are believed to have reached code red.”
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The Poconos were fortunate enough to avoid tornado damage this summer, but outbreaks in southeastern Pennsylvania and New Jersey may have reminded locals of the Cherry Valley tornado in 2009, and wondered whether it was increasingly likely that destructive tornadoes would strike.
Tornadoes need the wind shear and “a tremendous amount of instability, that is, heat and humidity,” to form, Gelber said.
Wind shear is not a climate change issue, Gelber said, but warmer surface water temperatures in the Atlantic Ocean and Gulf of Mexico are, so a tropical storm that landfall today is more likely to meet the instability requirement than a storm the water bodies were cooler.
“You basically load the dice more often,” he said. “If you happen to have the required wind shear – the winds turning with height and getting stronger – you have more opportunities to spin tornadoes than in the middle of the 20th century, for example, when the air was drier and a bit cooler, on average. “
Preliminary National Weather Service counts show 13 tornadoes in Pennsylvania on July 29, Gelber said, and seven from the remnants of Hurricane Ida in Pennsylvania and New Jersey on September 1.
Gelber noted a caveat for comparing total tornadoes, especially weaker tornadoes: The National Weather Service is making a bigger storm survey effort than before and now has the radar advantage. Doppler.
“I’m sure there are a bunch of EF-0 tornadoes that weren’t counted when I was young, and before that, because no one came out to watch,” he said.
As for the chances of tornadoes hitting the Poconos, it’s not impossible, but having a mountainous topography reduces the risk. “It disrupts the rotation,” Gelber said.
This summer, however, the Poconos weren’t in the danger zone to begin with. “Tornadoes like limits. In other words, the tornadoes will concentrate along the frontal limits where the wind changes direction, ”said Gelber, and that did not correspond to the Poconos during the two summer outbreaks.
Kathryne Rubright is a journalist who covers the environment, Northeastern Pennsylvania politics, and local news. She is based at the Pocono Record. Contact her at email@example.com.