What’s the difference between a tropical depression and a tropical storm?

THROUGHOUT history, the USA has been blighted by tropical weather disasters that have had devastating effects.

This includes tropical depressions and tropical storms which are considered some of the most common and dangerous.


Tropical depressions and storms can be leave cities flooded[/caption]

What is a tropical depression?

A tropical depression is categorised as one of the four stages of a tropical cyclone.

It forms when a thunderstorm grows higher and larger causing the air at the top to become unstable.

As the heat energy is released from the cooling water vapor, the air at the top of the clouds becomes warmer, making the air pressure higher and causing winds to move outward away from the high pressure area.

Winds in the storm cloud then created start to spin faster and faster, whipping around in a circular motion.

When the winds reach between 25 and 38 mph, the storm is considered a tropical depression.


Tropical Depressions form in the air[/caption]

What is a tropical storm?

When the wind speeds increases to reach between 39 and 73m mph, the tropical depression becomes a tropical storm.

Typically, the winds blow faster and start resemble a hurricane with a circular shape.

Most damage from tropical storms comes from heavy rainfall which can destroy buildings and cause severe flooding.

Landslides can also occur, blocking roads and railways and causing evacuation problems for the emergency services.

In the most extreme cases this can lead to a shortage of food and clean water.


The effects of Tropical Storm Claudette (2019)[/caption]

When were the last major tropical storms and depressions in the US?

The US has been subject to a number of storms and depressions in modern times– with the worst of those materialising into hurricanes.

From 2000 to the present, at least 28 tropical or subtropical cyclones affected the U.S. state of  Lousinina alone.

According to David Roth of the HPC, a tropical cyclone makes landfill along the coastline about two times every three years, and a hurricane makes landfall once every 2.8 years.

The most active month for tropical cyclone activity in the state is September, with ten total storms.


Water hits Florida’s coastline during Tropical Storm Eta (2020)[/caption]

Some of the major storms and hurricanes since 2000 include:

  • Tropical Storm Allison (2001)
  • Hurricane Isabel (2003)
  • Hurricane Charlie (2004)
  • Hurricane Jeanne (2004)
  • Hurricane Dennis (2005)
  • Hurricane Katrina (2005)
  • Hurricane Rita (2005)
  • Hurricane Ike (2008)
  • Hurricane Sandy (2012)
  • Hurricane Maria (2017)
  • Hurricane Dorian (2019)
  • Tropical Storm Claudette (2019)
  • Hurricane Zeta (2020)
  • Tropical Storm Eta (2020)
  • Tropical storms Amanda and Cristobal (2020)

Of this list, Hurrciane Katrina of 2005 caused the most fatalities and damage with 1,833 total deaths and over $100 billion in total damages.

While the most recent tropical storms of Amanda and Cristobal (2020) caused $956,000 of property damage in Florida alone.

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