Category 5 Atlantic hurricanes are rare. Only 7% of the 243 hurricanes observed since precise satellite measurements began in 1983 have reached this catastrophic intensity. And it is truly extraordinary to see a Category 5 hurricane as strong as Hurricane Dorian that made landfall on September 1, 2019 with sustained winds of 185 mph and gusts of up to 220 mph on Great Abaco Island in the Bahamas met. Winds of this magnitude would make Dorian worthy of a Category 6 rating, if there were one. (If you don't know me, you should know that there is already oneCategory 6is the name of a blog I co-author with Bob Henson at Weather Underground that specializes in daily updates on global tropical cyclone activity).
losSaffir-Simpson Hurricane Wind Scale, which is used to classify hurricane-force winds on a scale of one to five, stops at Category 5: 1-minute average wind speeds of at least 70 m/s (157 mph). If we add a category 6 to the scale, we have to take into account that the scale is not completely linear. For example, the winds of a Category 2 hurricane span a range of only 15 mph, but the winds of a Category 4 storm span a range of 27 mph. Regardless of this non-linearity, increasing the intensity by one category on the scale results in about four times the intensity more wind damage,according to the National Hurricane Center.
If we plot the scale (Figure 1 below) it is clear that a Category 6 should probably start with winds of 180-185mph. A Category 7 hurricane would have wind speeds of at least 210 - 215 mph. Using this logic, Hurricane Dorian would be classified as a Category 6 hurricane. Only one hurricane in world history would be classified as a Category 7 hurricane: Hurricane Patricia of 2015, the peaked with sustained winds of 215 mph off the Pacific coast of Mexico.
Using wind speeds of 185 mph as the Category 6 threshold, only five Atlantic hurricanes in recorded history would qualify. If we lower the threshold to 180mph, there are a total of eight that would qualify as Category 6:
- 190 mph: Allen 1980
- 185 km/h:dorio 2019, Labor Day 1935, Gilbert 1988, Wilma 2005
- 180 mph: Mitch 1998, Rita 2005, Irma 2017
It is truly rare for a hurricane of this hypothetical Category 6 intensity to make landfall. Dorian's winds of 185 miles per hour over the Great Abaco Islands and Grand Bahama tied it to the 1935 Labor Day hurricane in the Florida Keys for the strongest Atlantic hurricane on record. Expanding the Category 6 definition to include winds of 180 mph or greater would only add one additional Category 6 hurricane that made landfall in the Atlantic: Hurricane Irma of 2017, which made landfall in Barbuda, St. Maarten, and the British Virgin Islands with sustained wind spikes of 180 miles per hour
Dorian caused catastrophic damage, thanks in large part to its very slow movement of less than 5 mph over the Bahamas during the 27 hours it spent with a Category 5 force. This slow motion and extreme intensity allowed Dorian to subject the Bahamas to the most violent and sustained onslaught by an Atlantic hurricane on a settled location in recorded history. Preliminary estimates of damage in the Bahamas are $7 billion, more than 50% of the $12 billion GDP. The death toll as of this writing is 56, with around 600 people still missing.
Should the Saffir-Simpson scale be expanded to include a category 6?
Unfortunately, global warming increases the likelihood of ultra-intense hurricanes like Dorian (a topic I'll cover in a future post). From a climate change communications perspective, therefore, it makes sense to add a category 6 and a category 7 to the Saffir-Simpson scale to draw attention to this new generation of ultra-intense catastrophic hurricanes that are likely to become more frequent in the United States will be decades to come. However, because there would be so few of these Category 6 and 7 hurricanes, it would be difficult to conduct any meaningful statistical study of how they might alter with climate change.
However, any move to expand the Saffir-Simpson scale would have to come from the National Hurricane Center (NHC), and there is little expert support for such a move there. From a public safety/warning perspective, the NHC experts I've heard from believe that listing a Category 6 hurricane wouldn't do much good since a Category 5 hurricane is already considered catastrophic. In the continental US, for example, only four Category 5 hurricanes made landfall (1935, 1969, 1992, and 2018). The news that a Category 6 storm was coming would likely motivate people no more to take action to protect life and property than if a Category 5 storm was approaching.
Should the Saffir-Simpson scale be replaced?
Some hurricane experts believe the Saffir-Simpson scale should be dropped entirely. The original scale, introduced in 1971, included both wind speed and typical storm surge for each category. Over time, it became clear that the magnitude of the storm surge threat often did not correlate well with the Saffir-Simpson category of a hurricane. For this reason, the 2010 NHC removed the storm surge values, resulting in a pure wind scale.
A big problem remains: Most of the fatalities in hurricanes are caused by water (storm surge and freshwater flooding), not by wind. We need to create a system that warns people concisely about the magnitude of the threat to life and property from wind, storm surges and inland flooding, not just the magnitude of the winds.
With this in mind, the NHC deployed storm surge monitors and alerts during the 2017 hurricane season. However, these storm surge alerts do not provide quantitative measures of storm surges or their potential damage. A better solution might be to introduce a storm surge scale. One of these scales, called the Kuykendall scale orkscale, wassuggestedin 2018 by Penn State scientists Amanda Walker and David Titley. The scale's logarithmic base, ranging from zero to ten, makes it easy to communicate the meaning of the scale: each whole number increases bykresults in a tenfold increase in damage losses per capita.RMS.comhas another way to quantify potential damage from storm surges, using integrated kinetic energy (IKE), which also shows promise.
But that still leaves us without a good way to communicate the threat of inland flooding from a slow-moving hurricane that dumps catastrophic amounts of rain. Unfortunately, this threat is increasing as the forward rate of tropical cyclones (which includes all hurricanes, tropical storms, and tropical depressions) has declined 10% globally since 1949, according to aArticle 2018 in the magazineNatureby NOAA hurricane scientist Dr. Jim Kossin. Because they travel more slowly, tropical cyclones are more likely to bring heavier rainfall and increase the risk of flooding. Heavy rains also increase due to the extra amount of moisture evaporating into the air due to global warming. Category 4 Hurricane Harvey in Texas/Louisiana in 2017 ($128 billion in damage) and Category 1 Hurricane Florence in the Carolinas in 2018 ($24 billion in damage) were examples in themselves slow-moving storms whose risk of freshwater flooding was not adequately represented because of its Saffir-Simpson rating. So perhaps a new scale for inland flood risk is needed.
Local offices of the National Weather Service already doprovide detailed color-coded mapsshows the relative threat level of four different hurricane hazards: wind, storm surge, torrential rain, and tornado. But having three separate scales for wind, storm surge and rain risk might be too much for many people to swallow. Some nations in Europe have a simple system of yellow, orange, and red warning signals that convey the magnitude of the storm threat; maybe that should be used for hurricanes. This may be too simple, but we need something different than the current system.
The opinions expressed are those of the authors and not necessarily those of Scientific American.
ABOUT THE AUTHORS)
Jeff Masters served as a hurricane scientist with the NOAA Hurricane Hunters from 1986 to 1990. Thereafteralmost fatal flighthe left the Hurricane Hunters in Category 5 Hurricane Hugo to pursue a safer passion: in 1997 he received his PhD in air pollution meteorology from the University of Michigan. In 1995 he was a co-founder of thesubterranean climate, and served as its chief meteorologist until the company was sold to The Weather Company in 2012. Since 2005, his miracle blog (now calledCategory 6) is one of the web's most popular sources of information on extreme weather and climate change, and one of the most cited experts in the field. He can be reached atweatherman.masters@gmail.com.
Recent Articles by Jeff Masters
- April 2020: the second warmest April since records began on Earth
- March 2020: The second warmest March on Earth and the third warmest month on record
- First Category 5 tropical cyclone of 2020, Harold, Pound Vanuatu
FAQs
Was Hurricane Dorian a Category 6? ›
Hurricane Dorian was an extremely powerful and catastrophic Category 5 Atlantic hurricane, which became the most intense tropical cyclone on record to strike the Bahamas, and tied for strongest landfall in the Atlantic basin.
Is a hurricane Category 6 possible? ›There is officially no such thing as a Category 6 hurricane. But the idea of revising or adding to the scale has been discussed by some climate scientists who believe the current categories may not be adequate for increasingly extreme storms in the future.
How powerful is a Category 6 hurricane? ›In a 2019 FLORIDA TODAY guest column, he lobbied for creation of a new Category 6 hurricane — with fearsome sustained wind speeds of 180 mph or higher — atop the five-level Saffir-Simpson Hurricane Wind Scale.
Why isn t there a Category 6? ›There are no Category 6 storms for a reason—it would be pointless to make the distinction. Hurricane strength is rated using the Saffir–Simpson scale, first developed in 1971 by Herbert Saffir and Robert Simpson, a civil engineer and meteorologist respectively.
What is a category six? ›But now, scientists are toying with adding a Category Six, which would be reserved for so-called super hurricanes that have wind speeds that exceed the highest level of the current scale, which is Category Five. This is an idea that has been in floating around for a while now.
What level was Hurricane Dorian? ›The rapid intensification process continued, and the eye of 12 n mi in diameter became even more distinct, displaying a “stadium effect” sometimes observed in intense hurricanes. Dorian became a category 5 hurricane and then made landfall at Elbow Cay, Great Abaco, in the northwestern Bahamas (Fig.
Has there ever been a Category 6 tornado? ›There is no such thing as an F6 tornado, even though Ted Fujita plotted out F6-level winds. The Fujita scale, as used for rating tornados, only goes up to F5. Even if a tornado had F6-level winds, near ground level, which is *very* unlikely, if not impossible, it would only be rated F5.
How many hurricanes are in Category 6 in history? ›As of 2023, 19 storms have reached category 6 intensity. The strongest by pressure is Wilma of 2005, and the strongest by wind speed is Allen of 1980. The costliest is Katrina, also of 2005, and the deadliest is Mitch of 1998. All category 6 hurricanes have made landfall at at least hurricane intensity.
What is the strongest hurricane possible? ›Category 5 hurricane: Catastrophic damage will occur
In a Category 5 hurricane, the highest category hurricane, winds are 157 mph or higher.
Only one hurricane in world history would rank as a category 7: Hurricane Patricia of 2015, which peaked with 215-mph sustained winds off the Pacific coast of Mexico.
What was the strongest hurricane ever recorded? ›
With a wind speed of 185 mph at landfall, the Labor Day Hurricane of 1935 is the strongest hurricane ever to hit the United States.
How long did Hurricane Dorian last? › What category was Hurricane Dorian when it hit Nova Scotia? ›Dorian made landfall in Halifax shortly after 7 p.m. as a post-tropical storm, but had previously been a Category 2 hurricane with wind gusts of 141 km/h hitting parts of Nova Scotia.
Why don t you need to worry about a Category six hurricane? ›There isn't a “category six” because it's just not necessary given the catastrophic destruction left behind by a landfalling category five hurricane. Work on the Saffir-Simpson Hurricane Wind Scale began in the early 1970s through the research of meteorologist Bob Simpson and wind engineer Herbert Saffir.
What category was Katrina? › What is a Category 6 hurricane called? ›Is there such a thing as a Category 6 hurricane? Is there a Category 6 hurricane? No. Although there has been interest shown on search engines for a Category 6 hurricane classification, there is no such category on the Saffir-Simpson Hurricane Wind scale.
What is a Category 6 hurricane wind speed? ›Richard Olson is director of FIU's Extreme Events Institute. In a 2019 FLORIDA TODAY guest column, he lobbied for creation of a new Category 6 hurricane — with fearsome sustained wind speeds of 180 mph or higher — atop the five-level Saffir-Simpson Hurricane Wind Scale.
What cat storm was Katrina? ›Katrina was a large storm with a very distinct eye. Early on the 28th, Katrina reached a minimum central pressure of 902mb (at the peak) - ranking 7th lowest on record for all Atlantic Basin hurricanes - and rapidly intensified to a Category 5 (175mph).
Why was Hurricane Dorian so strong? ›The science connecting climate change to hurricanes like Dorian is strong. Warmer oceans fuel more extreme storms; rising sea levels bolster storm surges and lead to worse floods.
When did Hurricane Dorian become a Category 5? ›Rapid intensification occurred, and on August 31, Dorian became a Category 4 hurricane. On September 1, Dorian reached Category 5 intensity, with maximum sustained winds of 185 mph, and a minimum central pressure of 910 mb (26.87 inHg) while making landfall in Elbow Cay, Bahamas.
Has there ever been a Category 5 hurricane? ›
They are among the strongest tropical cyclones that can form on Earth, having 1-minute sustained wind speeds of at least 137 knots (254 km/h; 158 mph; 70 m/s). The United States National Hurricane Center currently estimates that a total of 38 tropical cyclones between 1851 and 2023 have peaked as Category 5 hurricanes.
When was the last EF5 tornado in the United States? ›The most recent EF5 tornado occurred on May 20, 2013 in Moore, Oklahoma. Caused tremendous damage to vegetation, large debris from leveled homes was carried at distance over 10 km (6.2 mi).
What was the weirdest tornado? ›Perhaps one of the weirdest tornado paths in recent years occurred west of Bennington, Kansas, on May 28, 2013. The tornado made a loop by first moving southeast, then turning north, before eventually tracking back to the southwest during its approximate one-hour-long life span.
What's the worst size tornado? ›The most "extreme" tornado in recorded history was the Tri-State Tornado, which spread through parts of Missouri, Illinois, and Indiana on March 18, 1925. It is considered an F5 on the Fujita Scale, even though tornadoes were not ranked on any scale at the time.
Has there ever been a Category 1 hurricane? ›Extensive damage to power lines and poles likely will result in power outages that could last a few to several days. Irene of 1999, Katrina of 2005, and several others were Category One hurricanes at landfall in South Florida. Winds 96-110 mph (83-95 kt or 154-177 km/hr).
Has there ever been a Category 8 hurricane? ›A Category 8 is a hypothetical Saffir-Simpson rating beyond the Category 5 rating which has never officially been recorded in human history.
What is the number 1 deadliest hurricane? ›| Rank | Name/Areas of Largest Loss | Deaths |
|---|---|---|
| 1. | Great Hurricane (Martinique, Barbados, St. Eustatius) | 22,000 |
| 2. | Great Galveston Hurricane | 8,000-12,000 |
| 3. | Mitch (Honduras, Nicaragua) | 9,086 |
| 4. | Fifi (Honduras) | 8,000-10,000 |
If the wind were perfectly level, you'd tumble along the surface, bouncing against the ground. However, if there were any updrafts, you could easily be lifted up and carried away. The good news is that 500 mph winds are rare. The strongest hurricanes have wind speeds around 200 mph with gusts up to 250.
What is the weakest hurricane? ›Tropical Storm Marco was the smallest tropical cyclone on record by radius of winds from center.
What is the oldest hurricane ever? ›The earliest hurricane to ever form was one that was unknown to hurricane specialists until a reanalysis of historical weather systems discovered its existence. In 2014, the National Hurricane Center found that an undocumented storm had actually become a full-blown hurricane on Jan. 3, 1938.
What is the largest storm on Earth? ›
Typhoon Tip was the largest tropical cyclone on record, with a diameter of 1,380 mi (2,220 km)—almost double the previous record of 700 mi (1,130 km) in diameter set by Typhoon Marge in August 1951. At its largest, Tip was nearly half the size of the contiguous United States.
What hurricane names will never be used again? ›According to the WMO's initial policy established in 2006, Greek-letter named storms could never be retired, "lest an irreplaceable chunk be taken out of the alphabet." Therefore, devastating 2020 hurricanes Eta and Iota would have been retired as "Eta 2020" and "Iota 2020" respectively, but the letter names themselves ...
Do hurricanes ever hit Africa? ›Climatological statistics. At least 32 tropical cyclones have affected Western Africa and its surrounding islands since records began in 1851. The majority of the storms affect West Africa and Cape Verde islands during the months of August and September which are the active months of a typical Atlantic hurricane season ...
What's the deadliest hurricane in US history? ›Galveston, Texas Hurricane of 1900
Considered the deadliest U.S. natural disaster, the Category 4 hurricane in Galveston, Texas, destroyed more than 3,600 buildings with 135 mph winds, according to the History Channel.
Merging Hurricanes
Another way a hurricane can have “two eyes” is if two separate storms merge into one, known as the Fujiwara Effect - when two nearby tropical cyclones rotate around each other and become one.
Hurricane Dorian was the strongest hurricane on record to hit The Bahamas. Once it made landfall, it hovered over the country --- sometimes moving at just 1 mph --- for more than 48 hours. All the while, it caused storm surges and wind damage, decimating parts of the archipelago.
Will Hurricane Dorian be retired? ›The name Dorian will be replaced by Dexter in the 2025 hurricane season.
How much damage did Hurricane Dorian cause? ›...
News releases.
However, the peak wind gusts with Fiona were higher than with Dorian. Dorian's landfall in the Halifax region meant the wind and rain field covered most of the Maritimes and Newfoundland, whereas the effects of Fiona were not as severe in southwestern Nova Scotia, western New Brunswick and eastern Newfoundland.
What hurricane was a cat 5? ›Those terrors were the Labor Day hurricane of 1935 that tore through Miami; Camille that struck the Gulf Coast near Mississippi in 1969; Andrew in 1992; and Michael in 2018.
What was the first hurricane to reach Category 5 status? ›
1992: Hurricane Andrew Hits Florida
In 1992, Hurricane Andrew became the first of these male-named hurricanes to reach Category 5 in the U.S.
...
| Category 7: The End of the World | |
|---|---|
| Preceded by | Category 6: Day of Destruction |
A Category 8 is a hypothetical Saffir-Simpson rating beyond the Category 5 rating which has never officially been recorded in human history.