Rising Summer Heat, Rainfall Half Again Avg. Totals Paved The Way For Ida To Wreck Philadelphia
Broadsided by floods and powerful tornadoes, the Philadelphia region was stunned by Ida’s deadly intensity. But to scientists, clues were abundant Ida might prove formidable when it made landfall near Port Fourchon, La., as a Category 4 hurricane on Aug. 29. The scene was set 1,100 miles away for it to make history here three days later. The Philadelphia region was already pumped full of water and primed by heat to make whatever remnant tracked its way even worse — a signature of climate change.
Consider that as Ida was forming in the tropics in late August, Philly’s weather had been much hotter and wetter than normal all month. The average temperature was 79.2 degrees -- 2.3 degrees above normal. And 6.18 inches of rain had fallen, 144% over the average for the last 20 years.
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Scientists say the connection between warming and climate change is well understood. A warmer, moister atmosphere generates more energy for storms to feed on. Based on an Inquirer analysis of moisture in the air, as measured by the dew points, 2021 was likely the muggiest summer since 1995. Looking at data from the last 50 years, Augusts in Philadelphia are getting hotter, leading to a 1.8-degree increase in average temperatures. And more days are cresting 90 degrees. So, a rainstorm that might have dumped 5 inches without a changed climate might dump 6 inches. While that might not seem like much, it translates to millions of gallons of additional water flowing into regional waterways.
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As big as Ida may seem, consider it was only little more than a year ago that remnants of Hurricane Isaias dumped 9 inches of rain in some local areas, caused the Schuylkill to overflow, flooded Boathouse Row, ruined homes in the city’s Eastwick neighborhood, and even trapped a dredge barge at the I-676 ramp to I-76 in Center City, forcing the road to close. During Ida, the Schuylkill at 30th Street Station in Philadelphia rose to 16.28 feet. Flood stage is nine feet, and 14 feet is considered a major flood. The average flow at the location is 1,460 cubic feet per second. It reached a flow of 125,000 cubic feet per second on Thursday.
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https://www.inquirer.com/science/climate/ida-climate-change-philadelphia-flooding-tornado-20210904.html