Here’s why you may hear tropical systems referred to as tropical cyclones

All low pressure systems are classified as cyclones worldwide

This satellite image provided by the National Oceanic and Atmospheric Administration (NOAA) shows a Tropical Storm Fred in the Caribbean as it passes south of Puerto Rico and the Dominican Republic at 8am EST, Wednesday, Aug. 11, 2021. (NOAA/NESDIS/STAR GOES via AP) (Uncredited)

ORLANDO, Fla. – Cyclones are nothing new. Any low pressure system, spinning counterclockwise in the northern hemisphere and clockwise in the southern hemisphere is a cyclone.

When these systems are in tropical regions, they are tropical cyclones, everywhere on Earth -- even in the Atlantic basin. There’s also a mid-latitude cyclone, a low pressure system found in the mid-latitudes. Nor’easters that impact the Mid-Atlantic and Northeast U.S. are mid-latitude cyclones.

To be a tropical cyclone, meteorologically speaking, certain criteria has to be met:

  • Gains strength by warm water
  • The center of circulation has to be closed, meaning complete counterclockwise air flow.
  • Continuous thunderstorm development around the center.

[RELATED: Here’s what a subtropical storm is | Tropical terms to know | Latest forecast, models updates on Tropical Storm Fred]

After the above criteria is met, it becomes a tropical depression in the Atlantic Basin. When wind speeds increase to 39 mph, it becomes a tropical storm and receives a name. When winds intensify to 74 mph, it becomes a hurricane.

In the Atlantic, we know tropical cyclones as tropical depressions, tropical storms and hurricanes.

Other parts of the world refer to these systems as something different, but anything that meets the aforementioned criteria is a tropical cyclone.

Tropical depressions, tropical storms and hurricanes are all tropical cyclones.

Any low pressure system on earth is a cyclone. A low pressure system in the tropics is a tropical cyclone. Each ocean basin refers to the tropical cyclone as something different.

Then what is a potential tropical cyclone?

The potential tropical cyclone designation is relatively new from the National Hurricane Center.

The name is given to a disturbance that hasn’t yet met all of the meteorological criteria to be a tropical cyclone, depression or storm in the Atlantic Basin, but will likely become one be and will also be impacting land within 48 hours.

You won’t see a potential tropical cyclone in the middle of the ocean; the NHC will wait until it fully develops into something tropical to classify it.

The National Hurricane Center created this potential tropical cyclone designation so they can issue watches, warnings and the official forecast, allowing for greater preparation time even though the system itself isn’t officially tropical by definition.

Once the criteria is met, the system becomes a tropical depression or tropical storm depending on the wind speed. This is why they are called potential tropical cyclones, rather than potential tropical storms.


About the Author:

Jonathan Kegges joined the News 6 team in June 2019 as the Weekend Morning Meteorologist. Jonathan comes from Roanoke, Virginia where he covered three EF-3 tornadoes and deadly flooding brought on by Hurricanes Florence and Michael.