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:
- The center of circulation has to be closed, meaning complete counterclockwise air flow.
- Continuous thunderstorm development around the center.
Tropical cyclones are fueled by warm ocean waters. There are also hybrid systems known as sub-tropical storms.
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 worldwide is a tropical cyclone.
Tropical depressions, tropical storms and hurricanes are all tropical cyclones.
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 has the potential to 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 meteorological 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.