Meteorological words can be difficult – like the word meteorological itself! I want to break down tropical terms and what they really mean as we near the start of the 2021 Atlantic hurricane season.
Let’s start with Hurricanes, Cyclones and Typhoons. The only difference between these is they happen in different geographical locations. In the Atlantic Ocean and northeastern Pacific Ocean, we call them Hurricanes. In the northern Indian Ocean, they are called Cyclones. In the northwest Pacific Ocean, they are called Typhoons.
Now to confuse you a bit further, Hurricanes and Typhoons are also referred to as Cyclones. In meteorology, a cyclone is a larger scale air mass that rotates around the center of low pressures – which is what Hurricanes, Typhoons and Cyclones are.
Below is a image courtesy of the World Meteorological Organization (WMO) displaying Tropical Cyclone Centers and their Region:
The difference between Tropical, Subtropical and Extratropical has to do with the temperature and energy profile within the storm.
- Extra-tropical systems derive their energy from a temperature difference from frontal boundaries.
- Tropical systems develop from getting energy from warm ocean waters.
- Subtropical is a hybrid of the two listed above. Subtropical systems have characteristics of both extratropical and tropical systems.
Here is a simple way to look at the three:
The stages of tropical development:
Tropical Depression: A tropical cyclone with maximum sustained winds of 38 mph (33 knots) or less.
Tropical Storm: A tropical cyclone with maximum sustained winds of 39 to 73 mph (34 to 63 knots).
Hurricane: A tropical cyclone with maximum sustained winds of 74 mph (64 knots) or higher. In the western North Pacific, hurricanes are called typhoons; similar storms in the Indian Ocean and South Pacific Ocean are called cyclones.
Major Hurricane: A tropical cyclone with maximum sustained winds of 111 mph (96 knots) or higher, corresponding to a Category 3, 4 or 5 on the Saffir-Simpson Hurricane Wind Scale.