For Donald Trump it always has to be superlatives. When the US President recently visited the Fema disaster control agency, the approaching hurricane “Dorian” was of course an issue – Trump even canceled a visit to Poland because of the danger posed by the hurricane to US states. The president said he knew there was warning level 5, but he had never heard of a hurricane that had actually reached this highest level.
As is so often the case when it comes to facts, Trump was wrong: during his tenure alone, there were four hurricanes of this highest category that swept across the US mainland.
Nevertheless: “Dorian” is definitely impressive and threatening.
The hurricane was only upgraded to Category 5 on Sunday. Storms only reach this highest area if they reach wind speeds of more than 250 kilometers per hour. The satellite image above, which NASA took with its Earth observation satellite “Aqua”, shows “Dorian” over the Bahamas. The picture was taken on Sunday at 2:05 p.m. (local time). At this point the eye of the storm was right over Great Abaco Island.
According to the US National Hurricane Center (NHC), “Dorian” is the strongest storm in the northwest of the Bahamas on record. There it caused massive damage: roofs were covered, cars overturned and power lines cut. According to the Red Cross, more than 13,000 houses have been damaged.
“Dorian” had reached the northern foothills of the island state on Sunday with winds of almost 300 kilometers. So far there is no precise information about the extent of the damage; it is likely to be considerable.
Now the cyclone could soon reach the coast of the United States – according to the latest forecasts, no earlier than Monday evening or Tuesday. According to recent estimates, it could just miss Florida, but still drive powerful storms to the coast. The states of Georgia or South Carolina could have a harder time: If the storm reaches the country here, there is a risk of damage such as covered houses, collapsed trees and electricity pylons as well as a collapse of the power and communication networks. High storm surges are also expected.
For the current hurricane season, which will last until the end of November, the National Weather Service Five to nine cyclones were predicted with a 70 percent probability, and up to four could reach high intensity.
Various factors are needed for hurricanes to arise: A windless low pressure area over the sea and warm water temperatures above 26 degrees. Then evaporated water rises, condenses and forms into large clouds.
Put simply, the storm absorbs huge amounts of energy through the water: the rise and condensation creates a negative pressure that drives it forward. As a result, more and more air flows upwards and is finally swirled around. A severe hurricane can release 50 to 200 trillion watts of energy. Most of it occurs as heat.
If the rotation of the air reaches a wind speed of around 120 kilometers per hour, one speaks of a category one hurricane. But the speed at which the entire hurricane system moves also plays a role. According to data from the NHC, “Dorian” is currently barely moving – he is moving west at less than two kilometers per hour.
This is not a reason to give the all-clear – on the contrary. Because cyclones bring devastating rain and floods with them, they often cause more destruction than the winds alone. If hurricanes hit land at low speeds, larger amounts of precipitation also rain down because they linger longer.
Researchers have long observed that hurricanes, typhoons and cyclones, as such storms are called, slow down depending on the region. On the other hand, the degree of destruction they cause increases. The category in which they are classified does not necessarily say anything about the amount of damage they cause on land. Storms with categories 1 to 3 have also been very destructive in recent years. Because of the climate crisis, cyclones won’t necessarily increase, but they could reach higher intensities, climate researchers believe.
After all, the National Hurricane Center recently announced that the hurricane will likely weaken. But it will remain a dangerous storm for the next few days. So the situation remains tense.