Convergence: Hurricane seasons to get wetter and more violent

Future hurricane seasons could see an increase in the number and severity of storms, according to a presentation at Convergence 2019.

Stalling hurricanes are becoming more of an issue for the re/insurance industry, according to Timothy Hall, senior research scientist, Goddard Institute for Space Studies, NASA.

Speaking at Convergence 2019, Hall said that Hurricane Dorian was an excellent example of a stalling storm, after it effectively stopped moving over the Bahamas this year, inflicting severe damage to the country.

Stalling tropical storms and hurricanes do not just bring high winds to coastal regions that they impacted, said Hall. They also severe amounts of rainfall, as Texas had experienced from Hurricane Harvey in 2017.

James Kossin, atmospheric research scientist at the National Oceanic and Atmospheric Administration, said that the Atlantic was currently in the middle of a warmer than average ocean temperature. There has also been lower wind shear, which seems to have led to a period of active hurricane activity.

However, he also said that ocean temperatures of the East coast of the USA were not increasing at the same rate as ocean temperatures in the tropics. Combined with high wind shear off the coast, this makes the area not conducive to hurricanes intensification at present.

Projections show that there is a strong chance that this might diminish over the next decade, said Kossin. This might have an impact on hurricanes that arrive in the area. By 2050 US hurricane risk could increase as a result.

Gabriel Vecchi, professor at Princeton University’s Department of Geosciences and Princeton Environmental Institute, said the number of storms recorded in each hurricane season has been trending upwards since records began in 1878. But this might be because of the lack of sampling in the days before satellite imagery, he added: once those data are included the trend is flat.

But Vecchi insisted current forecasts do project an increase in the number of hurricanes impacting the USA, as well as an increase in intensity and speed of intensification.

These mixed signals might be explained by historical aerosol use, dust and other climate-related factors, which could have masked century-scale greenhouse gas-related climate change, he said.

Increased urbanisation is also having an effect, he added. Newly paved areas increase the chances of flooding as the ground has reduced capacity to absorb rain, while the growing number of multi-story buildings increases the amount of turbulence by a small but measurable amount.