Extreme weather events require a complex set of components to occur. Scientists confirm that climate change is driving ocean warming and the tropical storm season is worsening worldwide. In the US alone, Florida was hit by two major hurricanes within a month of each other – one of which was described as the “storm of the century” by US President Joe Biden.
Hurricane Milton made landfall in Florida as a Category 3 storm on October 9 at 8:30 p.m. (local time) with sustained winds of 86 mph. Milton spawned at least 19 tornadoes, destroyed homes and knocked out power to more than 3 million homes.
A few weeks ago, the states of Florida and Georgia, North Carolina and South Carolina were devastated by Hurricane Helen. In May, Hurricane Beryl hit Jamaica in what was described as an “explosive start” to the annual hurricane season, as heavy rain is typically expected in the Atlantic and Pacific Oceans from June 1 to November 30.
Although major weather events such as these are common throughout the tropics, they require a complex combination of factors to come to fruition. And scientists warn that climate change is intensifying.
Multiple names for the same event
Different terms are used to describe the same extreme water phenomenon: tropical cyclone. It is called a typhoon in East and Southeast Asia, a typhoon in India and Australia, and a typhoon in North America. The terrestrial equivalent of these water hurricanes is the land hurricane. Unlike hurricanes, they can form whenever a storm occurs.
Temperature differences cause cold air to rush in and warm air to push upward. Tornadoes can be up to a mile in diameter, but are usually much smaller.
Whatever the name, these storms form in a similar way: when water above 26°C evaporates in the ocean. “A series of basic conditions are needed for a hurricane to form,” explains meteorologist Andreas Friedrich, a hurricane expert at the German Meteorological Service.
In addition to high temperatures, this ocean area must be large enough, at least a few hundred square kilometers. Formation of cyclones also depends on the presence of an area of low pressure.
“Mostly, small areas of low pressure move along the monsoon current off the west coast of Africa [ventos sazonais]Across the Atlantic, until it reaches these warm waters”, continues Friedrich. A hurricane only forms when there are no large wind differences near the ocean surface or at high altitudes, which can disperse the storm.
Explosive mixture
When all of this happens, an area of low pressure becomes a cyclone: warm, moist air from the ocean condenses at higher, cooler altitudes, creating negative pressure over the clouds and ocean surface. Large volumes of air from the surrounding area are drawn into the storm.
These air masses are drawn upwards like a chimney, producing winds of up to 350 kilometers per hour. The Coriolis inertial force associated with the Earth's rotation keeps the masses in rotation.
“In the center of this vortex, the typical 'eye' of a hurricane forms, where there is calm and no clouds, while the clouds at the edge of the eye accumulate higher and higher,” reports Friedrich.
Slower moving storms are more destructive
If hurricane-friendly conditions persist, the storm will be more destructive. “Cyclone is driven by air currents at a height of 5 to 8 km. They determine where the hurricane is headed.”
When a hurricane makes landfall, it usually loses strength quickly. High-altitude air currents quickly push the storm inland, separating the main energy source of warm, moist air from the ocean. There, they weaken and become low-pressure systems, losing their destructive power.
However, if a tropical cyclone moves very slowly and is constantly fueled by moist ocean air near the coast, it can cause severe damage.
Strong weather due to climate change
Although the frequency of hurricanes and tornadoes has not increased, climate change is making their intensity worse, serious meteorologists believe.
Tropical cyclones gain much of their energy from the heat of water vapor trapped in the ocean. According to an analysis of North Atlantic tropical cyclones published in the journal Scientific Reports in 2023, as surface temperatures rise, hurricanes absorb more water vapor.
In addition to increasing hurricane intensity, this trend makes it difficult for meteorologists to reliably predict when and where hurricanes will strike. “Large ocean areas with temperatures of 26 degrees Celsius are large areas where hurricanes can form,” concludes Friedrich.
An analysis of scientific reports corroborates this statement, estimating that current hurricanes can double from a weak hurricane (Category 1) to a strong one (Category 3 or higher) within 24 hours.
In addition, the Atlantic and Caribbean regions where tropical cyclones occur also changed in response to ocean warming during the study period.
