Atlantic hurricanes may be losing their ‘seeds’

Researchers have found a key detail that helps them understand how some hurricanes form over the Atlantic Ocean – alongside the possibility they might be getting less common.

Hurricanes and tropical cyclones need a very precise set of circumstances to form, although the conditions that create them in certain places are still poorly understood.

A new study by US researchers has found that more moisture in African weather patterns makes it harder for hurricanes to form in the Atlantic.

The study is published in the Journal of Advances in Modeling Earth Systems.

The researchers used a weather and climate model to examine “African easterly waves”, an eastward-moving ocean and atmospheric phenomenon that often turns into tropical cyclones.

“Considerable work during the last two decades has emphasized the role of deep moist convection to explain the development of African easterly waves,” says lead author Kelly Núñez Ocasio, a scientist at the US National Center for Atmospheric Research.

“But, the precise role of moisture has proven somewhat elusive. With the development of new modelling capabilities, I was able to focus on the role of moisture in cyclogenesis stemming from the hurricane seed.”

Atmospheric moisture is predicted to increase as the climate warms. This has led to variable predictions for the formation of tropical cyclones and hurricanes – in Australia, tropical cyclones are predicted to become fewer, but more intense.

This study found that increased moisture led to a lower chance of a cyclone forming.

“When I increased the moisture we saw more convection and thunderstorms, which is to be expected; however, we discovered that the waves struggled to pair with the more intense and deep convection,” says Núñez Ocasio.

“With increased moisture, the energy source of tropical cyclone seeds moved north and further away, reducing the kinetic energy available to the African easterly wave, which led to weak, energy-starved tropical cyclone seeds.” 

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