Difference between Tropical Storm and Hurricane

Published on March 9, 2016

Meteorologists generally divide severe tropical storms into hurricanes, typhoons, and tropical cyclones. In the following article, we will see what the differences are between a hurricane and the other tropical storms.


Tropical Storm vs Hurricane
An image of a subtropical storm named Lee before making its landfall

A tropical storm is one of the most destructive weather systems on the planet Earth. They are accompanied by strong forced winds, torrential rains, and massive pressure falls; all of that happens simultaneously. Essentially, a tropical storm is a system of thunderstorms, characterized by surface circulation and accompanied by sustained winds with speeds of 39-73 miles per hour. At this point a tropical storm is assigned with a name, depending on the area where it usually takes place.

Generally, there are three main category names of tropical storms.

Cyclones. These happen around the Indian Ocean and the South-East Pacific. Cyclones tend to appear in countries like Madagascar, India, and parts of Australia. They also often attack countries like Japan, and Indonesia, Malaysia, and nearby countries.

tropical cyclones
A collage of images of various tropical cyclones

Typhoons happen in the North-Western Pacific basin and in the proximity of the Philippines, China and the Marshall islands.

Typhoon named Nesat
Typhoon named Nesat, which in 2011 hit the Philippines resort area

Hurricanes (the name is derived from the Spanish word for the Caribbean God of storms – Juracan) are tropical storms that occur in the Caribbean and parts of the South-Eastern United States of America. Most hurricanes emerge thousands of miles away from these areas – in the Atlantic ocean, close to North-West Africa. Hurricanes receive their energy from warm seas, and can only develop when the sea temperature is at least 26 degrees Celsius, developing into major hurricanes only when the sea temperature is at least 28 degrees Celsius. That is the reason why they never occur in northern parts of the globe.

The physical process of a hurricane developing:

Hurricanes require one of two elements to form: either wave patterns or thunderstorms. Neither of these is found in the areas of high pressure, where the atmosphere is stable. There are other limitations, for example, wind patterns in the outer layers of the atmosphere and the force of the rotation of the Earth mean that hurricanes can only develop around the equator, between 20 and 8 degrees north of the equator, to be precise. This seems like a not a big area, but it is the area where the easterly surface winds (known in meteorology as trade winds) converge; there is a lot of moisture there. This makes the perfect conditions for developing thunderstorms and makes it a place where most hurricanes originate.

When trade winds meet, the warm air heavily laden with water vapor is forced to rise. In a cooling air pattern, water vapor condenses into droplets, and there is a change of vapor into liquid, which releases latent heat, which, in its turn, warms the atmosphere, thus making it gradually more buoyant. The air starts to rise with increased pace, producing more and more thunderclouds. When the trade winds arrive on the curved part of the planet, there is the inception of a tropical storm, because of the rotation of the latter. As the wind grows larger, more moist air is thrown onto the surface, more water vapor condenses into cloud droplets, and more latent heat is released. This leads to increased rotation. When the surface wind reaches sustained speed of over 7 miles an hour, this storm is called in meteorology a category 1 hurricane.

The basic structure of a matured hurricane
The basic structure of a matured hurricane

As the air inside the thunder clouds of a hurricane cools, it becomes denser and falls again; there is an alternating pattern of storm clouds with clear slots in between. This is what contributes to the appearance of a hurricane as a spiral, a familiar image which is seen in satellite images of hurricanes taken from above.

As a hurricane grows and intensifies, it develops the distinctive structure that looks like a hole (known in meteorology as “the eye”) in the middle of swirling massive clouds (known as “eyewall”, an area about 16 to 80 kilometers). The latter is the most destructive part of a hurricane, containing very strong winds and destructive thunderstorms.

Hurricanes are measured on a scale from 1 to 5, depending on the winds’ strength and damage potential.

  • Category 1: 74- 95 mph. Damage potential: minimal
  • Category 2: 96-110 mph. Damage potential: moderate
  • Category 3: 110-130 mph. Damage potential: extensive
  • Category 4: 131-155 mph. Damage potential: extreme
  • Category 5: more than 156 mph. Damage potential: catastrophic

Hurricanes can bring devastating side effects. Here is one example of a massive hurricane:

In August, 2005 a hurricane named Katrina (level 5) hit the city of New Orleans. This hurricane has become known as one of the most expensive natural disasters in history. It blew a wall of sea water (8 meters high), known as a storm surge, ahead of it, and as a result it engulfed most of the city of New Orleans.

Hurricane Katrina it in 2005
Damage to Long Beach, gulf port Mississippi after Hurricane Katrina it in 2005

Meteorologists are getting better at forecasting the strength and directions of hurricanes and can roughly predict how many hurricanes will happen in each Atlantic hurricane season, information that is valuable to the insurance industry.

Tropical storm vs Hurricane

What is the difference between tropical storm and hurricane?

In meteorology, there have been several attempts to divide tropical storms into distinct categories. The most common way to do that is to divide them according to the region where they occur. Hurricanes happen in the Caribbean and parts of the South-Eastern USA, while cyclones and typhoons – the other two types, hit other areas of the planet.

Comparison chart

Tropical stormsHurricanes
Are generally divided into typhoons, cyclones, and hurricanesIs one type of tropical storm
Occur anywhere on the planet, except its northern partsOccur in the Caribbean and parts of the South-Eastern USA