What is the difference between a typhoon and a hurricane?

Question: What is the difference between a typhoon and a hurricane?  Will they be affected differently by climate change?

Typhoon Haiyan (NASA photo)

Typhoon Haiyan (NASA photo)

Jonathan Comstock, research support specialist in the Department of Horticulture, replies:

‘Typhoon’ and ‘hurricane’ are regional names for the same kind of storm.  They are both special names given to tropical cyclones (large regional storm systems forming over warm tropical ocean water and rotating around a central eye) that have grown strong enough to have very damaging effects.  If you were somewhere bordering the Western North Pacific Ocean, that is, in the Philippines, the coast of China or Japan, and experiencing such a tropical storm with sustained winds over 74 mph, you would be in a typhoon that has moved off the Pacific ocean and hit land. If you were having a similar experience in the Eastern North Pacific Ocean (Hawaii to the Mexican coast) or in the North Atlantic Ocean (Caribbean, Gulf of Mexico and east coast of North America), you would be in a hurricane.  A ‘Super Typhoon’ is the equivalent of a very strong category 4 or a category 5 Hurricane.

Despite being the same as individual storms, there are also some important differences for the people living in these different regions.  Because of the very large expanse of warm, tropical ocean in the western Pacific and other global atmospheric patterns, typhoons are more common than hurricanes.  On average, there are 25 to 30 storms that rise to the status of a named typhoon every year, and only 6-10 that become named hurricanes.  The likelihood of a storm gaining strength to become either kind of named storm depends in part on large-scale atmospheric patterns as well as ocean temperatures.  These atmospheric patterns are so large that when conditions are good in the western North Pacific for forming typhoons, they aren’t so good in the North Atlantic for forming hurricanes, and vice versa.  For this reason it is not common to hear about major storms occurring in both regions at once.

Even though they don’t often happen at the exact same time, both hurricanes and typhoons are most common in the months of June through November.  Around the North Atlantic basin, this period is often referred to as ‘Hurricane season’, and it is relatively unheard of to experience a hurricane mid-winter. Only 4 winter hurricanes have been recorded since 1886.  In contrast, although typhoons have the same peak season, they can occur in mid-winter as well and on average there are two winter-month typhoons every year.

Is climate change making typhoons and hurricanes worse?  This is an area of intensifying study by climate scientists.  Because storm systems are so complex, with many interrelated factors affecting their formation and strength, climate scientists are not yet certain about the impact of climate change.  Some argue that warming oceans will feed more powerful storms, but others counter that the required atmospheric conditions might be affected by climate change in a way that actually inhibits storm development.  The changing balance of all these factors is not yet clear, and could even turn out to be different in different ocean basins. The most recent Intergovernmental Panel on Climate Change concluded that for Atlantic hurricanes, at least, there was a likelihood that climate change might increase the intensity of the biggest storms while the total number of storms could actually decrease.



Category: Climate Change Q&A

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