The Makings of a Category 5 Hurricane

Fagjun | Published 2017-09-08 21:41

Hurricane Harvey, a category 4 hurricane, brought devastation to the areas it hit. Now, Hurricane Irma, a category 5 hurricane, is bound to be worse.



Satellite image of Hurricane Irma by NASA



At the time of this writing, Irma has just hit the Caribbean island of Barbuda, where winds are at sustained speeds of 174kilometers per hour, with gusts of 250 kilometers per hour. According to the Saffir-Simpson hurricane wind scale, this is what a category 5 will be like:


Catastrophic damage will occur: A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas.


Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months.”


Hurricane Irma is certainly fearsome, but surprisingly, it's not invincible. Category 5 hurricanes are rare, as well as reliant on certain conditions in order to sustain itself. Still, they're certainly a force to be reckoned with.



Building a Category 5 Hurricane


Satellite image of Hurricane Irma when it was still just a category 3 hurricane [Image by UWM/SSEC/CIMSS, William Straka III]



So what makes a category 5? A hurricane reaches the top of the Saffir-Simpson scale when its peak winds exceed a speed of 281 kilometers per hour, which Irma has exceeded. At these speeds, the hurricane will be able to cause 500 times more damage than a category 1 with winds of 153 kilometers per hour.


In general, sea waters heated up to a temperature of at least 27 degrees Celsius fuel hurricanes. However, this isn't enough to form a category 5. Warm waters must be present, but there also shouldn't be much wind shear, or upper-level winds, in the hurricane's path. Too much wind shear will disrupt the hurricane's rotation. These are the environmental conditions necessary for sustaining a category 5 hurricane like Irma.


However, hurricanes can also lose power if they hit a large enough island. In the case of Hurricane Irma, for example, it will weaken considerably if it hits Cuba or Hispaniola.


For live updates on hurricane Irma, click here.


Unfortunately, Irma seems set to sustain its strength. Reports say that the waters ahead of Irma have a temperature of 29 to 30 degrees Celsius. Wind shear is also expected to stay low, presenting no disruptions to the hurricane. Thus, environmental conditions are ripe for sustaining Hurricane Irma's strength.



Another Historic Storm


The devastation wrought by the 1935 Labor Day Hurricane, which was also a category 5 [Photo by Bettmann, Getty Images]



However, it's not really as simple as all that. Hurricanes are quite complex, which means that Irma can still fluctuate in strength. Take, for example, the hurricane's eyewall. The eyewall contains the strong winds that blow around a hurricane's eye, the calm of the storm. It's possible that a second eyewall will form, causing the first eyewall to disintegrate and weaken the hurricane's winds. However, if waters are still warm and the wind shear is still low, the hurricane can regain its strength.


So far, only three category 5 hurricanes have made landfall in US history. These are the Labor Day hurricane, Hurricane Camille, and Hurricane Andrew, which made landfall in 1935, 1969, and 1992, respectively. Even if Hurricane Irma weakens before it makes landfall, being a category 5 hurricane, it's still bound to be a historic storm.


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