Is a Category 6 hurricane possible? What research says

RALEIGH, N.C. (WNCN) – As of Tuesday morning, Hurricane Milton is a Category 4 storm, but it spent part of Monday as a Category 5 storm, the highest possible on the Saffir-Simpson strength scale.

Research published earlier this year, however, suggests another category could be added to the scale.

Hurricanes have been getting stronger thanks in part to warmer ocean waters linked to climate change, study authors Dr. Michael Wehner and Dr. Jim Kossin explained. Because of this, they suggested a hypothetical Category 6 could become the top step on the Saffir-Simpson scale.

Currently, the Saffir-Simpson scale has five levels based on a storm's sustained wind speed:

Saffir-Simpson Hurricane Scale	Wind Speed (in miles per hour)
Category 1	74-95 mph
Category 2	96-110 mph
Category 3	111-129 mph
Category 4	130-156 mph
Category 5	157 mph or higher

As of Tuesday morning, the National Hurricane Center says Milton's maximum sustained winds are 150 mph, making it a strong Category 4. On Monday, while Milton was a Category 5 storm, maximum sustained winds were around 160 mph.

That put it just within Category 5 strength. While strong, that wouldn't be enough for it to be considered a Category 6 storm based on Wehner and Kossin's hypothetical suggestion.

The pair suggested in their study that Category 5 be capped with sustained winds of 192 mph and a Category 6 would be anything above that threshold.

Speaking with Nexstar's WFLA in February, Wehner confirmed that between 1980 and 2021, the period with the best data, there were 197 tropical cyclones to reach Category 5 intensity. Of those, five exceeded the Category 6 status proposed by Wehner and Kossin — they all occurred in the last nine years of the period analyzed.

Wehner explained to Jeff Berardelli, WFLA's chief meteorologist and climate specialist, that based on his potential intensity analysis, the Gulf of Mexico has the greatest risk of being hit by one of these potential Category 6 storms.

“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 at the time.

But would adding another strength category help, or would it decrease the apparent severity of the other categories?

National Hurricane Center Director Dr. Michael Brennan had this to say when asked for comment in February:

"At NHC, our focus is on steering towards the individual hazards, which include storm surge, wind, rainfall, tornadoes and rip currents, instead of the particular category of the storm, which only provides information about the hazard from wind. Category 5 on the Saffir-Simpson scale already captures 'Catastrophic Damage' from wind, so it's not clear that there would be a need for another category even if storms were to get stronger. In addition, most deaths in tropical cyclones occur not from the wind but from water - storm surge, rainfall/inland flooding, and hazardous surf - causing about 90 percent of tropical cyclone deaths in the United States. So, we don't want to over-emphasize the wind hazard by placing too much emphasis on the category."

Other meteorologists have argued that adding a sixth category would only "add to the hype." Several told The Associated Press they think another category could give the wrong signal to the public because it’s based on wind speed, while water is by far the deadliest killer in hurricanes.

Hurricane Helene, for example, reached maximum sustained winds of 140 mph before making landfall in Florida last month. While it left severe damage in Florida, conditions were arguably even worse as it reached the Carolinas and Tennessee, battering some mountain towns to the brink of extinction.

The death toll from Helene has surpassed 225, making it the deadliest hurricane to hit the mainland U.S. since Katrina in 2005. About half of the victims were in North Carolina while dozens more were killed in Georgia and South Carolina.

The Associated Press contributed to this report.