Meteorologists expected Hurricane Milton, which hit the Florida coast on Thursday, October 10, to reach a non-existent Category 6. However, the “apocalypse” did not actually happen as the hurricane suddenly began to weaken. On the coast, its strength dropped first from Category 5 to Category 3, and then to Category 2. Nevertheless, the question remains: can a hurricane of such a strength that humanity has never encountered before really form? And is there a limit to the power of hurricanes on Earth, and what does it depend on?
The strength of hurricanes has a limit, but it is not constant. Photo source: yamal-media.ru
Contents
- 1 How hurricanes are classified
- 2 What can be the maximum wind speed on Earth
- 3 What determines the speed of hurricanes
- 4 The limit of hurricane wind speed is constantly increasing
How hurricanes are classified
The Saffir-Simpson scale from 1 to 5 is used to classify hurricanes. Category 1 hurricanes, the weakest ones, are characterized by wind gusts of up to 119 km/h. The highest category, category 5, is assigned to hurricanes with sustained winds, the speed of which reaches 250 km/h.
It should be said that this classification is based solely on wind speed, but does not take into account damage from winds and floods, unlike, for example, the earthquake intensity scale. Let us recall that the latter is based on the severity of the consequences.
Hurricane Milton was not as strong as expected – it weakened from Category 5 to Category 2 on land. Photo source: sobcor.news
What can be the maximum wind speed on Earth
So, when we talk about the strength of a hurricane, we mean its wind speed. Currently, the conventional limit of wind speed, which is called the maximum potential intensity, is about 320 km/h. Why conventional? We will talk about this in more detail below.
It must be said that many people mistakenly believe that it is the strong gusts of wind of hurricanes that are the main destructive force that leads to the death of mass casualties during a natural disaster. But in fact, this is not the case. Hurricanes are indeed one of the most dangerous natural disasters, but if you look at the worst natural disasters in human history, you will find that the most deadly thing during hurricanes is the storm surge, which leads to sudden flooding.
The conditional speed limit for hurricanes is 320 km/h. Photo source: rus.delfi.ee
But let's get back to wind speed. What is its limit and why can't it exceed the conventional value of 320 km/h? As you remember from your school physics course, energy does not arise from nothing and does not disappear into nowhere, but can only transform from one form to another. Accordingly, for a hurricane to occur, a powerful source of energy is needed. This source is the heat of the ocean. But, since the water temperature is limited, the wind speed of hurricanes is also limited.
What determines the speed of hurricanes
Ocean water temperature is an important factor in hurricane wind speed, but it is not the only one. Air temperature and cloud top temperature also play a role, determining how quickly heat can move from the sea surface to the top of the storm. So-called “wind shear” — the difference in wind speed and direction at different altitudes in the atmosphere — also plays a role.
Wind shear acts as a brake on a hurricane, preventing it from reaching its full potential. Too much shear can tear a storm apart. According to one study, wind shear caused only 20% of storms between 1962 and 1992 to reach 80% or more of their maximum potential intensity. However, storms have recently begun to approach their theoretical maximum.
The strength of a hurricane depends on the temperature of the ocean water and several other factors. photo source: straitstimes.com
Knowing the data of all the factors affecting the wind speed of a hurricane, scientists can predict it quite accurately. However, as we can see from the example of Hurricane Milton, it is not always possible to predict its behavior, including sudden attenuation, as happened this time.
The limit of hurricane wind speed is constantly increasing
Although the limit of hurricane wind speed exists, it is not absolute. Recently, due to global warming, there has been an increase in water temperature in the world's oceans. In the last few years, scientists have been recording new temperature records that do not last long.
Accordingly, as the water warms, the power of hurricanes will increase. In fact, scientists are already observing this trend. For example, one study showed that between 1979 and 2017, the share of major hurricanes increased by 8% per decade. This means that over 30 years, the share of powerful hurricanes has increased by almost a quarter.
Super-powerful hurricanes may become common in the near future. Photo source: dlubal.com
According to scientists, super-powerful hurricanes, which were previously a rarity, will soon become commonplace due to global warming. In addition, record-breaking hurricanes will occur periodically. Therefore, it will be necessary to expand the five-point scale for assessing their power. Most likely, not only category 6, but also category 7 will be required for an accurate classification of hurricanes.
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Researchers have identified several storms that can already lay claim to non-existent categories. For example, Hurricane Patricia of 2015 is currently considered the most powerful. Its wind speed reached 345 km/h, that is, exceeded the maximum. True, it was not the most destructive, since by the time it reached land, the wind had weakened to 240 km/h.