Eye on the Tropics

Hurricane, tropical storm and tropical depression: What's the difference?

There are a ton of weather terms that might be easy to confuse including hurricanes, tropical depressions and tropical storms. Here’s the difference.


Tropical disturbance: forms over waters of at least (80F). It is an area of organized thunderstorm activity 100 - 300 miles in diameter which maintains its identity for 24 hours or more, and it's in the lower levels of the atmosphere (surface). If the disturbance acquires a spin, and winds of at least 30 mph. It is now called a tropical depression.


Tropical depressions form when a low-pressure area is accompanied by thunderstorms that produce maximum winds below 39 mph.

What's the forecast? 2018 Hurricane forecast: NOAA Predicts near- or above-average season

As for tropical storms, those are more severe. Depressions become storms when winds reach between 39 and 73 mph. They also must follow a cyclone pattern to become a storm.

Hurricanes are a step up from a tropical storm, with winds of more than 74 mph. Hurricanes are further rated into five categories based on their wind speed:

Category 1: 74-95 mph

Category 2: 96-110 mph

Category 3: 111-129 mph

Category 4: 130-156 mph

Category 5: above 157 mph

Trees bend in the tropical storm wind along North Fort Lauderdale Beach Boulevard in 2017 (Photo by Chip Somodevilla/Getty Images)

However, all three types of storms are fueled by warm, moist air near oceans in tropical areas.