Future hurricanes: Stronger, slower, wetter
the costliest on record.
It’s been challenging for scientists to study how hurricanes might change in the future as the climate continues to warm. Most climate models, which are usually run on a global scale over decades or centuries, are not run at a high enough resolution to “see” individual hurricanes.
Most weather models, on the other hand, are run at a high enough resolution to accurately represent hurricanes, but because of the high cost of computational resources, they are not generally used to simulate long-term changes in climate.
For the current study, the researchers took advantage of a massive new dataset created at NCAR. The scientists ran the Weather Research and Forecasting (WRF) model at a high resolution (4 kilometers, or about 2.5 miles) over the contiguous United States over two 13-year periods.
The simulations took about a year to run on the Yellowstone supercomputer at the NCAR-Wyoming Supercomputing Center in Cheyenne.
The first set of model runs simulates weather as it unfolded between 2000 and 2013, and the second simulates the same weather patterns but in a climate that’s warmer by about 5 degrees Celsius (9 degrees Fahrenheit) — the amount of warming that may be expected by the end of the century.
Drawing on the vast amount of data, the scientists created an algorithm that enabled them to identify 22 named storms that appear with very similar tracks in the historic and future simulations, allowing the hurricanes to be more easily compared.
As a group, storms in simulations of the future had 6 percent stronger average hourly maximum wind speeds than those in the past. They also moved at 9 percent slower speeds and had 24 percent higher average hourly maximum rainfall rates. Average storm radius did not change.
Each storm unique
“Some past studies have also run the WRF at a high resolution to study the impact of climate change on hurricanes, but those studies have tended to look at a single storm, like Sandy or Katrina,” Gutmann said.
“What we find in looking at more than 20 storms is that some change one way, while others change in a different way. There is so much variability that you can’t study one storm and then extrapolate to all storms.”
But there was one consistent feature across storms: They all produced more rain.
While the study sheds light on how a particular storm might look in a warmer climate, it doesn’t provide insight into how environmental change might affect storm genesis. That’s because the hurricanes analyzed in this study formed outside the region simulated by the WRF model and passed into the WRF simulation as fully formed storms.
Other research has suggested that fewer storms may form in the future because of increasing atmospheric stability or greater high-level wind shear, though the storms that do form are apt to be stronger.
“It’s possible that in a future climate, large-scale atmospheric changes wouldn’t allow some of these storms to form,” Gutmann said. “But from this study, we get an idea of what we can expect from the storms that do form.”
— Read more in Ethan D. Gutmann et al., “Changes in Hurricanes from a 13-Yr Convection-Permitting Pseudo–Global Warming Simulation,” Journal of Climate 31, no. 9 (6 April 2018) (doi: org/10.1175/JCLI-D-17-0391.1)
