Climate change may fuel extreme weather in Pennsylvania

The number of tornadoes in Pennsylvania, New Jersey and Delaware increased by 600% in the past five years – a dramatic rise in a region once relatively safe from twisters.

The average tornado wind speed has risen, too. It’s not uncommon for tornadoes to reach wind speeds of 100 miles per hour. 

These extreme weather events are particularly jarring in the Delaware Valley near Philadelphia, where Hurricane Ida’s remnants produced seven tornadoes that ripped through the valley in 2021.

Scientists are studying the extent to which these weather systems are linked to climate change.

Climate scientists predict warmer and wetter days on the horizon for Pennsylvanians, alongside more historically rare weather events.

One 2018 study found that over the past four decades, tornado frequency has increased in a large swath of the Midwest and Southeast United States.

The study conducted by meteorology professor Victor Gensini of Northern Illinois University and Harold Brooks of NOAA’s National Severe Storms Laboratory, noted an eastward uptick in tornado frequency.

Researchers examined tornado frequency trends in fine-scale resolution via two approaches. 

First, they tracked tornado reports over decades. Then, they looked at regional trends in daily frequency of tornado-environment formation over that same period, using an index called the Significant Tornado Parameter, or STP.

The number of reported tornadoes and the STP analysis both revealed an eastward trend.

Gensini said understanding these trends can help government leaders prepare for associated costs and protect residents.

“This could be taken into consideration when adopting building codes, identifying potentially impacted community assets, creating awareness and making emergency preparations,” he said.

Although there’s an increase in the number of documented and reported tornadoes in the region, researchers are still exploring how these patterns are related to climate change.

Penn State Climatologist Kyle Imhoff in 2019 told StateImpact Pennsylvania that a rise in reported tornadoes may linked, in part, to higher populations and more smartphones filming these storms.

“We certainly have evidence flash flooding and heavy rainfall will be impacted by climate change,” he said. “Whether you get tornadoes or not, there are still a lot of questions about that.”

Extreme weather conditions could affect all corners of Pennsylvania.

Climate-related challenges are expected to affect infrastructure, public health, population and water resources. Pittsburgh may see a population boom of “climate migrants” – those fleeing areas hit hardest by climate change.

To mitigate climate impacts, city leaders have incorporated climate projections into stormwater-control regulations to brace for more frequent rainstorms and worsening flooding.

Located at the confluence of three rivers tucked into populated hillsides, Pittsburgh is particularly vulnerable to flooding. Much of the city’s infrastructure is a century old; improving roads, bridges and stormwater systems will be vital in the coming decades.