Extreme Weather Fall Outlook: Warm, Wet and Stormy

After a summer of extreme heat that has wreaked havoc on power grids and infrastructure in many places, the United States is looking ahead to a fall season full of weather that is just as tumultuous and disruptive. While some risks are in the rear view – extreme heat and fire season are mostly on the way out, for example – the country will likely have to contend with new risks as hurricane season peaks and the El Niño weather pattern returns. Guarding against and recovering from these extreme weather events is top of mind for many policymakers this week, as the UN General Assembly met for a special Climate Ambition Summit intended to foster new funding and new ideas for climate adaptation, and environmental activists gathered outside to call for a faster green transition for Climate Week. As global leaders debate at the macro level, individuals and businesses must plan for weather-related disruptions, even as weather predictions become more and more difficult.

Fall Landscape

In addition to crisp weather and changing leaves, autumn brings with it new weather risks that are only intensified as climate change continues to warp global weather patterns. The biggest climate risk looming in coming months is the projected impact of El Niño, the warm phase of a weather cycle that repeats every two to seven years. The warm wind pattern will bring warmer, wetter weather to the entire U.S., and effects will only be amplified by climate change. El Niño technically began in June, although its effects typically rise in autumn and peak around Christmas. While much of the complex weather pattern is not understood, researchers warn that it (and its cooler counterpart, La Niña) may be getting longer in duration.

Broadly, El Niño will cause the southern U.S. to be wetter than usual, and the North will likely see a warmer winter than in previous years. In the 1980s, a strong El Niño caused record flooding in California, washing away roads and causing home-destroying mudslides, and severe drought in Indonesia and the Philippines. In 2016, the weather pattern contributed to what is still the hottest year on record. This year, experts predict record rains and flooding in much of the southern U.S., which could cause similar infrastructure and home destruction as in the 1980s, as well as a balmy winter for the North that could disrupt agriculture and farming (also in the 1980s, a warm winter caused by El Niño in Alaska likely reduced the salmon harvest). Warmer, wetter months can increase bug-borne illness as well; more habitats for fleas and mosquitoes have caused increased cases of plague and West Nile virus in the U.S. in previous El Niño weather cycles.

The other main weather risk on the horizon going into fall is an unusually severe Atlantic hurricane season. The ocean warmth that brings about El Niño fuels hurricanes, while high-level winds that the weather pattern also brings usually have a dampening effect of shearing storms apart in the atmosphere. Prior to the beginning of the season, researchers predicted a normal season, but an early summer explosion in Atlantic Ocean heat supercharged storm creation and has precipitated an unusually destructive season. The average hurricane season typically begins in June and concludes in early November, with peak activity in early to mid-September; this year, however, researchers say that it is unlikely that hurricane activity has reached its peak. Fourteen named storms have already developed in the Atlantic, typically the average for an entire season. The warm ocean allows storms to develop longer, leading to more chance that they become large enough to classify as hurricanes and contribute to more rapid intensification – leading to storms like Idalia, Franklin, and Lee, which grew in intensity extremely quickly, catching researchers off guard. With the extreme water temperatures, researchers expect the eastern U.S. to see up to seven more named storms this year before the season finally winds down.

Extreme Weather Risks and Outlook

Extreme weather risks are rising as climate change continues to impact earth’s weather systems, and risks to individuals and businesses are increasing. In 1980, the U.S. experienced three billion-dollar weather events; since January, the U.S. has seen 23. Costs for local governments, businesses and individuals to recover from these events are rising, especially as higher-risk areas become harder (or even impossible) to insure. Whether dealing with the fallout from more frequent or wider-ranging hurricanes and tropical storms, making repairs from destructive mudslides caused by extreme rains, or losing out on days of productivity, costs will remain high for those dealing with extreme weather this fall.

Another risk moving forward is that unpredictable weather events as a result of climate change are making it more difficult for weather prediction models to accurately guess what is next. Many companies are looking to AI-based weather prediction, which “learns” from the data set of past weather events to make faster, more accurate weather predictions, as the future of weather prediction becomes increasingly consequential to businesses of all kinds. However, increasingly intense weather events are complicating AI’s ability to do this; more and more frequently, weather events are the most extreme example of their type. Increasingly, those affected by the weather must not only carefully monitor predictions and prepare for projected events, but also expect the unexpected.