The only thing 100% predictable about hurricanes is their constant change.

Powered by the energy of warm waters and winds and common in regions such as the Atlantic Ocean, these atmospheric phenomena are a challenge for citizens and weather experts because of their instability.

It is necessary to follow them step-by-step through radar and satellites to predict their behavior and thus prepare for any eventuality that poses a risk to life and property.

And one of the changes that surprises meteorologists and climate experts the most is that, as the cause is still not entirely clear, the so-called Whirlwind eyewall replacement.

This event, which usually occurs in major category 3, 4, and 5 hurricanes, can alter the impact of a cyclone once it lands.

fully on tuesday hurricane ian, A strong category 4 cyclone with sustained winds of over 240 km/h has gone through the eyewall replacement process.

It did so just after it struck the state of Pinar del Río in Cuba and before it hit the state of Florida in the US, where it wreaked havoc from its strong winds and a large storm surge.

eye wall

The first thing you should know is US National Hurricane Center (NHC for its English abbreviation), these atmospheric phenomena have a structure that is divided into three parts: the eye, the eyewall, and the rain bands.

Rain bands have clouds and strong thunderstorms that move in a spiral that creates winds and sometimes hurricanes. The eye is a relatively quiet area, a center around which precipitation bands rotate.

And the wall is completely area closest to the eye. “The eyewall consists of a ring of long storms that produce heavy rain and often the strongest winds,” says the NHC for this hurricane region.

Changes in the structure or wall of the eye can make a cyclone’s winds stronger or weaker. “The eye can grow or shrink and a double wall can form,” continues CNH.

Wall change and its effects

Eyewall replacement often occurs in more severe hurricanes, meteorologist Ernesto Rodriguez told BBC Mundo. US National Weather Service

Ranging from category 3 to 5 on the Saffir-Simpson scale, these cyclones have sustained winds of more than 178 km/h.

“What happens is that a larger storm wall begins to surround and suffocate the inner core that originally formed. The new storm ring surrounds the wall of the oldest eye, and this eventually disappears,” says the expert.

Once they go through this process, which usually happens when the hurricane is about to get stronger, the storm stops getting stronger.

«It is that they go through cycles in which the diameter of the eye changes. Eye change keeps them [a los huracanes] they are stable and then intensifying again,” adds Rodriguez.

The expert cited Hurricane Maria, which hit Puerto Rico in 2017, as an example. The storm was category 5 with sustained winds of 257 km/h, but was reduced in strength just before hitting the area during the eyewall replacement. category 4, wind 249 km/h.

But when an eyewall replacement is made, the strongest and most dangerous part of the hurricane results in a larger diameter.

“The larger the eye’s diameter, the more areas there will be that will be affected by stronger winds,” says Rodriguez. This means that the most destructive areas will reach more land.

Eyewall replacement can occur more than once.

In the case of Hurricane Ian, its original eye was 20 nautical miles in diameter and was 75% wider at 35 nautical miles after the eyewall was replaced.