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Expert says the Gulf of Mexico has the greatest risk to experience a potential Category 6 storm.
TAMPA, Fla. (WFLA) — As the Earth warms, more heat energy is available to fuel stronger hurricanes. A new study finds that tropical cyclones are indeed achieving greater peak winds and that the trend will continue into the future.
With this in mind, the two authors of the study, Dr. Michael Wehner and Dr. Jim Kossin — both leading researchers at the intersection of hurricane and climate change research — investigate the question of whether it’s time to add another category — a Category 6 with winds of 192 mph or greater — to the Saffir-Simpson scale.
The authors’ opinion is that the open-endedness of the 5th category of the wind scale becomes increasingly problematic for conveying wind risk in a warming world. They suggest a 6th category may help communicate that climate change has caused the winds of the most intense tropical cyclones to become significantly higher.
The study released Monday in the Proceedings of the National Academy of Sciences states, “We find that a number of recent storms have already achieved this hypothetical Category 6 intensity and based on multiple independent lines of evidence examining the highest simulated and potential peak wind speeds, more such storms are projected as the climate continues to warm.”
WFLA’s Chief Meteorologist and Climate Specialist, Jeff Berardelli, spoke with Wehner over email Monday to discuss the risk to populations along the Gulf of Mexico Coast. Alarmingly, Wehner explained that from his potential intensity analysis, the Gulf of Mexico has the greatest risk of being hit by one of these potential Category 6 storms in the Atlantic Basin.
“The potential for a cat 6 storm is already there in the Gulf of Mexico and the Caribbean. And any intense storm in the Gulf will make landfall somewhere,” Wehner said. “So your viewers and followers should be aware that climate change has already increased the risk of intense hurricanes in the Gulf and that risk includes storms of unprecedented ferocity.”
Wehner added that the risk continues to increase as temperatures warm even under the modest global warming levels. In other words, the risk grows as long as the climate continues to warm.
The Gulf of Mexico has warmed around 2 degrees F (1.2 degrees C) since around 1980. A 2 degree F increase in water temperature translates to a potential increase in hurricane intensity of ~20 mph.
The paper defines a Category 6 storm as one where the peak sustained winds reach 192 mph or greater, a simple extrapolation of the Saffir-Simpson scale, which currently is open ended at a Category 5 with winds of 157 mph+.
Globally, 197 tropical cyclones reached Category 5 intensity from 1980 to 2021, which is the period of highest quality data. Remarkably half of the 197 occurred in the last 17 years of the period. Even more remarkably, 5 of those storms exceeded the hypothetical Category 6 and they all occurred in the last 9 years of the record.
Of the 5 storms, none have yet occurred in the Atlantic Basin. Typhoon Haiyan in the West Pacific and Hurricane Patricia in the East Pacific are two examples which would have been classified as Category 6 storms.
While it may seem like semantics, the damage potential increases exponentially as wind speed increases, such that a proposed Category 6 could indeed inflict substantially more damage than a low-end Category 5.
To make it easier to understand, here are a few examples.
First, let’s compare a storm with winds of 75 mph to a storm with double the winds — 150 mph. It may seem reasonable to conclude the 150 mph storm would do double or quadruple the damage. But that’s not even close. According to NOAA, a storm with winds of 150 mph does 250 times the damage of a storm with winds of 75 mph.
So what about a Category 5 vs a Category 6? In 2010, The Tampa Bay Regional Planning Council put out a scenario where a hypothetical Category 5 (160 mph) wind storm hit Tampa Bay causing $250 billion in damage.
But what if that storm were a Category 6 intensity? According to NOAA, the potential damage from a storm with winds more than 190 mph has 4X the damage potential, raising the potential cost to a trillion dollars!
In the image below, taken from the paper, you can see that potential intensity of tropical cyclones increases as the world continues to warm. The top left shows 1.5 degrees C warming above pre-industrial levels, which the planet will reach around 2030.
The scale increases to +2C, +3C and +4C of future global warming and as temperatures warm you can see the shades of orange grow darker and become red, indicating the increase in potential tropical cyclone intensity. In the Atlantic the colors are most prominent in the Gulf of Mexico.
As it stands right now, the most plausible scenario is that humans may be able to arrest global warming before it reaches +3C. Time will tell. But by then potential intensity will have reached alarming levels.
Still there are many meteorologists who do not agree with adding a category 6. Some feel that Category 5s already accurately describe a catastrophic storm and that adding a category may just add to hype. Others feel that the Saffir-Simpson scale does need reform, but not necessarily to add a category, more so to incorporate hazards from water, not just wind.
Regardless, research shows the proportion of extreme tropical cyclones will continue to increase and so will rapid intensification. The question is, will adding a Category 6 raise awareness? The fact that it is even being discussed has likely already started to achieve that goal.
