The Atlantic hurricane season will be “extraordinary”

Image source, NOAA/Getty Images

Screenshot, Hurricane Lee, above, rapidly intensified into a Category Five hurricane last year.

  • Author, Mark Poynting
  • Role, weather reporter

The North Atlantic could see up to seven major hurricanes of category three or more this year, which would be more than double the usual number, the US meteorological agency NOAA warned.

Normally three major hurricanes would be expected in a season.

Up to 13 Atlantic hurricanes of category one or higher are forecast for the period from June to November.

Record high sea surface temperatures are partly to blame, as is a likely shift in regional weather patterns.

While there is no evidence that climate change is producing more hurricanes, it is making more powerful ones more likely and causing heavier rainfall.

“This (hurricane) season looks extraordinary,” NOAA Administrator Rick Spinrad said at a news conference.

Unlike in the Atlantic, NOAA had already forecast a “below normal” hurricane season in the central Pacific region, where a move into La Niña has the opposite effect.

On average, the Atlantic basin – which includes the Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico – experiences 14 named tropical storms per year, of which seven are hurricanes and three are major hurricanes.

Tropical storms become hurricanes when they reach maximum sustained wind speeds of 119 km/h (74 mph). “Major” hurricanes (category three and above) are those that reach at least 178 km/h (111 mph).

In total, NOAA expects between 17 and 25 named tropical storms, of which eight to 13 could become hurricanes and four to seven could become major hurricanes.

The highest number of major hurricanes in a single season in the Atlantic is seven, observed in both 2005 and 2020. NOAA’s forecast suggests 2024 could approach that number.

The exact causes of individual storms are complex, but two key factors are behind the forecast.

First, there is the likely change from El Niño to La Niña in the coming months, which helps these storms grow more easily.

And second, sea surface temperatures are much warmer than usual in the main hurricane development region of the tropical Atlantic.

That often means more powerful hurricanes, because warmer waters provide more energy for storms to grow as they move westward.

“All the ingredients are ready” for an intense hurricane season, said Ken Graham, director of the US National Weather Service.

To draw attention to the way global warming is making higher intensity storms more likely, a recent study explored the possibility of creating a new category six level.

This “would alert the public that the stronger tropical cyclones we are experiencing now are unprecedented and the reason is warming of the ocean surface due to climate change,” explains the study’s lead author, Michael Wehner, senior scientist at Berkeley Earth. .

Hurricane categories only take wind speed into account. But these storms pose other significant dangers, such as rainfall and coastal flooding, which are generally worsening with climate change, NOAA warned.

Warmer air can retain more moisture, increasing the intensity of precipitation.

Meanwhile, storm surges (the short-term rises in sea level caused by hurricanes) are now occurring on a higher base. This is because sea levels are now higher, mainly due to melting glaciers and warming seas.

“Sea level rise increases the total depth of flooding, making today’s hurricanes more damaging than last year’s storms,” ​​says Andrew Dessler, a professor of atmospheric sciences at Texas A&M University.

Given the active forecast, researchers emphasize the need for the public to be aware of the dangers these storms can pose, particularly “rapid intensification events,” in which the speed of hurricane-force winds increases very quickly and, therefore, Therefore, they can be especially dangerous.

“We’re already seeing overall increases at the faster rate at which Atlantic hurricanes are intensifying, which means we’re probably already seeing increased risk of hazards to our coastal communities,” explains Andra Garner, an assistant professor at Rowan University in USA.

“Rapid intensification of storms may still be difficult to predict, which in turn intensifies the challenges that arise when trying to protect our coastal communities.”

Graphics by Erwan Rivault and Muskeen Liddar

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