What is the difference between typhoons and hurricanes?
I have been living in the mainland United States since 15 August 2015, but I was born and raised on the island of Guam, southernmost of the Mariana Islands in western Micronesia. On Guam, we identify powerful rainstorms with rotating bands of destructive winds as typhoons. In the mainland United States, however, storms with these same characteristics are identified as hurricanes. Why is that? Are typhoons and hurricanes truly distinct from each other? Or is this just an arbitrary naming system?
Image: Typhoon Mawar
What are typhoons and hurricanes?
Typhoons and hurricanes are both a type of tropical cyclone. The National Hurricane Center defines tropical cyclones as a weather phenomenon that takes shape over tropical or subtropical waters, has a closed low-level circulation, and moves as an organized and rotating system of clouds and thunderstorms. Tropical waters spans from Earth’s equator to the 30th parallel in both Northern and Southern Hemispheres. Subtropical waters span from the 30th parallel to the 40th parallel on both hemispheres. According to the NASA Global Precipitation Measurement, tropical cyclones are formed when heat is pulled from warm ocean surfaces into rotating horizontal winds. The National Oceanic and Atmospheric Administration (or NOAA) points out that tropical cyclones can occur in four levels of intensity: tropical depressions with max sustained windspeeds of 38 mph (33 knots) or less, tropical storms with max wind sustained windspeeds of 39-73 mph (34-63 knots), hurricanes with max sustained windspeeds of 74-110 mph (64-95 knots), and major hurricanes with max sustained windspeeds of 111 mph (96 knots) or higher. NOAA gives slightly different windspeed parameters for typhoons and super typhoons with the former having max sustained windspeeds of 74-149 mph (64-129 knots) and the latter having max sustained windspeeds of 150 mph (130 knots) or more. The National Ocean Service defines a knot as one nautical mile per hour (or the speed of a body moving over the surface of water) where 1 nautical mile is equal to 1.15 miles.
Do typhoons and hurricanes only happen in certain times of the year?
Tropical cyclones require certain environmental conditions to be in place for enough time for them to form, including pre-existing weather disturbance, warm tropical oceans, moisture, and relatively light winds. Because of this, they are more likely to occur in certain times of the year. For 2024, NOAA estimates that hurricane season may span from 1 June to 30 November while typhoon season may span from 1 July to 15 December. Environmental conditions influencing when hurricane and typhoon seasons occur are greatly effected by the El Niño and La Niña weather patterns. El Niño and La Niña weather patterns are fascinating, so an explanation of will those be saved for a future Science in a Nutshell post.
Do typhoons and hurricanes spin in opposite directions?
A common misconception is that the key difference between typhoons and hurricanes is the direction in which they spin: clockwise (spinning to the right, in the same direction as an analog clock) or counterclockwise (spinning to the left, in the opposite direction of an analog clock). But this is not what makes typhoons and hurricanes different from each other. The direction in which a tropical cyclone spins is determined by the Coriolis effect. The Coriolis effect is the curved path that moving bodies—like trade winds and ocean currents—in our climate, weather, and oceans tend to follow as a result of the Earth’s rotation. The direction of these curved paths is determined by the location of the moving body in relation to the Earth’s equator. In the Northern Hemisphere (everything above the equator) ocean currents are deflected to the right, so cyclones north of the equator rotate counterclockwise. In the Southern Hemisphere (everything below the equator) ocean currents are deflected to the left, so cyclones south of the equator rotate clockwise.
Do typhoons and hurricanes occur in different places?
According to NOAA, typhoons and hurricanes do not occur in the same places on the planet. The key distinction between typhoons and hurricanes is in which part of Pacific, Atlantic, or Indian Oceans they form. If a cyclone stronger than a tropical storm occurs in the North Atlantic, central North Pacific, or eastern North Pacific, it is identified as a hurricane. If a cyclone stronger than a tropical storm occurs in the Northwest Pacific, it is called a typhoon. Any cyclone that forms in the South Pacific and Indian Ocean, regardless of intensity, is referred to as a tropical cyclone.
Closing Thoughts
Typhoons and hurricanes are essentially the same type of tropical cyclone. They are given different names because typhoons form in the Northwest Pacific while hurricanes form in the North Atlantic, central North Pacific, and eastern North Pacific. This naming system is useful because it identifies which broad part of the world these cyclones form and occur in. Considering that the North Atlantic and North Pacific are both in the Northern Hemisphere, typhoons and hurricanes both rotate in a counterclockwise direction.
Dångkulo' na' saina ma'åse'! Thank you so much for reading this Science in a Nutshell post!
Notes:
Random Thoughts posts are brief summaries of much larger topics.
Underlined text are hyperlinked to referenced sources.
Text in bold brown font are important terms to remember.
Post Date: 24 August 2024
