Scale of hurricane strength – is a sixth category needed?

Skala siły huraganów

The Saffir-Simpson Hurricane Strength Scale has been used for 55 years to assess wind strength and warn residents of impending danger. However, recent studies show that with a warming climate, hurricanes are getting stronger and are increasingly going beyond their current scale. Should scientists add a new category in the classification of these violent weather events? Could it help and how?

Saffir-Simpson hurricane strength scale

The aforementioned classification method is based on a five-point scale. The first degree describes a hurricane with wind speeds of 119 to 153 km/h, while the fifth degree describes a hurricane with wind speeds of 252 km/h and above. Meanwhile, on February 5 this year. in an American scientific journal Proceedings of the National Academy of Sciences an article was published, whose authors asked themselves: is this scale still valid? By broadcasting messages based on this classification system, can the government inform citizens of the true extent of the threat?

The paper’s authors, Michael F. Wehner and James P. Kossin, analyzed data from 1980 to 2021. During this period, 5 hurricanes were recorded, which researchers classified as the sixth category, which does not yet officially exist, that is, those with winds of at least 309 km/h. All cases occurred in the last 9 of the years analyzed. The current hurricane strength scale has the disadvantage that its fifth degree has no upper limit. This means that the communicated threat level remains constant, no matter how much the wind speed exceeds 252 km/h. Increasingly, this does not reflect the seriousness of the situation, as their destructive potential is growing exponentially, and there will be more and more such storms as the climate warms.

Controversy over the sixth step of the scale

Both Kossin and Wehner were co-authors of the The 11th chapter of the IPCC’s 2021 report concluded that it is likely that the global proportion of tropical cyclone events falling into categories 3-5 has increased over the past four decades. This inspired Kossin to look into these phenomena. I don’t remember when the idea of defining category 6 came up, but I remember that I immediately reacted negatively,” he said. Why?

He stated that with his eyes he sees people refusing to evacuate because it is only category 5. He was concerned about the normalization of increasing risk – an adaptive strategy for people trying to cope with the increasing risks of climate change. Unfortunately, it is also a strategy that puts people at great risk. However, he understood, as did Wehner, that we need a scale of hurricane strength to help more effectively protect people from the effects of hurricanes. In the modern world, such storms mean that you really can’t do anything but get out of their way. It seems to us that this is a really important thing for the public to understand. (Wehner)

The need for more precise warnings is demonstrated by the situation of Filipinos who were hit by Typhoon Haiyan in November 2013. It has killed more than 6,300 people and destroyed or damaged more than a million buildings. Humanitarian workers discovered that some people had died in shelters built to withstand the effects of the category’s storms. 5 However, Haiyan’s wind speeds and storm surges were much stronger than any previously recorded in the Philippines. They exceeded the category 5 level by more than 64 km/h. This typhoon also hit the Gulf of Mexico and the western Pacific, where the number of hurricane-force winds is forecast to even double. 6. in the near future.

Global warming brings more rain

Kevin Reed, associate professor of atmospheric sciences at Stony Brook University in New York, said climate change is associated with increased rainfall during hurricane season. This is because the oceans generate more energy as they warm, which is discharged in the form of storms, and the strength and intensity of these storms are already increasing at the formative stage. Warmer water causes stronger evaporation and increases the moisture level in the atmosphere, and is therefore associated with more precipitation.

In contrast, Kerry Emanuel, an MIT expert on the subject. He said that for 35 years now, scientists have been expecting an increase in the thermodynamic speed limit for hurricane winds. However, it is not the wind speed that is the greatest weakness of the Saffir-Simpson scale. The problem is that it does not cover water-related risks. Most hurricane damage, injuries and fatalities are the result of its actions. Wehner and Kossin believe that the hurricane strength scale should be expanded to a sixth degree, although this will not solve all problems. However, this is a step toward improving people’s safety, which should be done as soon as possible.