Extreme weather events require a complex combination of elements to occur. Scientists confirm that climate change is causing the oceans to warm and the intensity of bad weather to increase. Tropical storm season appears to be worsening around the world. In the United States alone, within a month, two major hurricanes hit the state of Florida, one of which was defined by American President Joe Biden as the “storm of the century”.
Hurricane Milton made landfall in Florida as a Category 3 storm at 8:30 pm (local time) on October 9, with winds of approximately 86 miles per hour. Milton also spawned at least 19 tornadoes, destroyed homes and cut power to more than 3 million homes.
Just a few weeks earlier, Florida and the states of Georgia, North Carolina, and South Carolina had been devastated by Hurricane Helene. In May, Hurricane Beryl hit Jamaica, described as an “explosive start” to the annual storm season, as heavy rain is normally expected from June 1 to November 30 in the Atlantic and Pacific oceans.
While major weather events like these are routine in the tropics, they require a complex mix of ingredients to happen. And scientists also warn that climate change is increasing in intensity.
Many names for the same phenomenon
Many different terms are used to describe the same extreme water event: tropical cyclone. It is called a typhoon in eastern and southeastern Asia, a cyclone in India and Australia, and a hurricane in North America. Tornadoes are the terrestrial equivalent of these water cyclones. Unlike hurricanes, they can form any time there is a storm.
The temperature differences cause cold air to penetrate inside and warm air to be pushed upwards, in an increasingly rapid spiral. Tornadoes can be up to a mile in diameter, but are generally much smaller.
Regardless of the name they are given, these storms form in a similar way: when water above 26°C evaporates over the sea. “Hurricanes need a number of fundamental conditions to form,” explains meteorologist Andreas Friedrich, a tornado expert at the German Meteorological Service.
In addition to the high temperature, this sea area must be quite large, at least a few hundred square kilometers. Hurricanes also depend on the presence of a low pressure area to develop.
“Often small areas of low pressure move off the west coast of Africa with the monsoon current [ventos sazonais]across the Atlantic to these warm waters,” Friedrich continues. A hurricane can only form when there are no large wind differences near the sea surface or at higher altitudes, which would disperse the storm.
Explosive combination
If all this happens, a low-pressure area can develop into a hurricane: warm, moist air from the sea rises to condense at higher, colder altitudes, forming clouds and negative pressure at the sea surface. Large volumes of air are drawn into the storm from the surrounding area.
These air masses are then pulled upwards like a chimney, generating winds of up to 350 kilometers per hour. The Coriolis inertia force, which is related to the rotation of the Earth, causes masses to rotate.
“In the center of this vortex the typical ‘eye’ of a hurricane forms, where there is total calm and there are no clouds, while the clouds at the edge of the eye accumulate higher and higher,” Friedrich reports.
Slow-moving storms are more devastating
The longer conditions favorable for hurricanes persist, the more destructive the storm will be. “Hurricanes are pushed by air currents at an altitude of between 5 and 8 kilometers. They determine where the hurricane goes.”
When a hurricane makes landfall, it generally loses strength quickly. High-altitude air currents will soon push the storm inland, separating it from its main energy source, warm, moist ocean air. There they weaken and transform into low-pressure systems, losing their destructive power.
However, if a tropical cyclone moves very slowly and continues to be fed by moist ocean air near the coast, it can cause serious damage.
Stronger weather due to climate change
Even if the frequency of hurricanes and cyclones is not increasing, extreme weather experts believe climate change is worsening their intensity.
Tropical cyclones get most of their energy from the heat of water vapor they capture in the ocean. As surface temperatures rise, hurricanes absorb greater volumes of water vapor, according to an analysis of North Atlantic tropical cyclones published in the journal Scientific Reports in 2023.
In addition to increasing the intensity of hurricanes, the trend is making it harder for meteorologists to reliably predict when and where hurricanes will hit. “The larger the ocean areas with temperatures above 26°C, the larger the regions where hurricanes can form,” concludes Friedrich.
Scientific Reports’ analysis appears to support this claim, estimating that current hurricanes are twice as likely to evolve from a weak (category 1) to a strong (category 3 or more) hurricane within 24 hours.
Additionally, the Atlantic and Caribbean regions where tropical cyclones occur also changed in response to warming oceans during the study period.
Source: Terra
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