Paulette, Rene, Sally, Teddy and Vicky. Not the main characters in a new series, but the names of five <strong>tropical storms over the Atlantic Ocean. Thats special: the last time there were so many at the same time was almost forty years ago.
Hurricane Sally is slowly landing in the Gulf of Mexico near Alabama and Florida. The storms are causing great inconvenience: 150 000 houses are without electricity and authorities are warning of flooding.
Sally will not be the last storm. The US weather bureau NOAA had predicted it would be a boisterous year for the beginning of the hurricane season (from June to November). In fact, there are so many storms now that there is a good chance that the weather bureau will have run out of names prematurely this year.
On average, twelve tropical storms pass over the Atlantic Ocean in a season. Of those twelve, there are normally around eight hurricanes, three of which are heavy, devastating hurricanes. There are already twenty tropical storms this year. How is it possible that there are so many all of a sudden?
According to hurricane expert Rein Haarsma of KNMI, there are a few explanations, but the most important is the climatic phenomenon La Niña. Because of this natural phenomenon, it is a little less warm above part of the Pacific Ocean around the equator. This has an effect on the wind above the Atlantic Ocean. There, at high altitudes, the wind is less strong and tropical storms are therefore less likely to be nipped in the bud.
“You have to imagine, youre sitting with your camping burner somewhere on the campsite and its windy. Then those flames are blown out”, explains Haarsma in the CCeit Radio 1 News. “The winds do the same thing at high altitudes with tropical storms. But because of La Niña those winds become less, so the hurricanes can develop better”
Climate change does not necessarily play a role when it comes to the number of hurricanes, explains Haarsma. “We dont expect more hurricanes as a result of climate change. That sounds a bit strange, because hurricanes extract their energy from the heat of seawater. So you would expect more
However, there is something else going on. In the tropics, the temperature in the air heats up even harder than on the earths surface, which in turn means that the atmosphere becomes more stable. As a result, there are fewer hurricanes. “But when they are there, they get stronger.”
The fact that there are so many storms at the same time is the result of natural fluctuations, says Haarsma. Climate models do not show an increase in the number of storms, and observations over a longer period of several years confirm that picture. The number of hurricanes varies from year to year, for various reasons. “It has to do with whether or not there is a strong La Niña effect, but also with the African monsoon and with the sea water temperature. There are also major fluctuations
There is only one name left for this storm season: Wilfred. In the event of further storms, the weather bureau will have to rely on letters from the Greek alphabet.