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Published: June 18, 2021

What's the difference between a tropical disturbance, depression, storm | Weather

A tropical disturbance -- officially known as Potential Tropical Cyclone Three -- is currently in the Gulf of Mexico with impacts expected along the Gulf Coast and in metro Atlanta.

(MORE: Flash Flood Watch for Atlanta this weekend)

You'll probably hear a lot of terms used to describe this system over the next few days.

The most important message with this tropical system is that it will produce heavy rain and strong winds along the Gulf Coast regardless of what it's actually called. It will also produce rain for north Georgia.

Listed below are the common terms you'll hear when describing tropical systems.

Tropical wave/disturbance 

A tropical system usually starts as a tropical wave or tropical disturbance. This is simply a collection of showers and storms in the tropics with no circulation or circulation that is not well-defined. 

Even though a tropical wave or disturbance isn't officially a tropical cyclone, they can still produce heavy rain and strong winds.

Tropical cyclone

Once a tropical wave or disturbance shows clear, low-level circulation, it's officially designated as a tropical cyclone and will fall into one of three categories based on wind speed:

  • Tropical depression - tropical cyclone with maximum winds under 39 mph.
  • Tropical storm - tropical cyclone with winds between 39-73 mph.
  • Hurricane - tropical cyclone with winds of at least 74 mph.
  • Major hurricane - tropical cyclone with winds of at least 111 mph.

Naming storms

Once a tropical cyclone becomes a tropical storm or hurricane, it's given a name. Names are not given to tropical depressions. 

Storm names are determined by the World Meteorological Organization and are recycled every six years, unless a storm is so destructive that its name is retired.

Three names were retired from the record 2020 hurricane season.

(MORE: Tropical Weather Center)

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