Rare tornadoes hit northern Sweden
The Local · 25 Jul 2015, 17:57
Published: 25 Jul 2015 17:57 GMT+02:00
- Rare Swedish twisters surprise eye-witnesses (02 Jun 12)
- Tornadoes leave northern Sweden reeling (05 Jun 11)
- Tornado strikes in southern Sweden (08 Jun 08)
“I was a bit worried about a boat that was a little too close to the tornado,” Hansi Gelter told Swedish newspaper, Expressen.
Gelter saw a tornado form over the sea at Piteå. “I had just got inside the door trying to escape the rain, when the wife screamed ‘Look, a tornado!' I ran straight upstairs and fetched the camera.”
The tornado lasted about 5-10 minutes before disappearing. “I was never afraid. I saw that the tornado was moving away from us.”
Just outside Luleå, Malin Steding was awoken at 0600 by a thunderstorm. “My husband shouted that he saw a tornado and I hurried to try to photograph it,” she told Expressen.
“I made sure my cats stayed indoors. You do not want them to be sucked up!”
Though scientists don't entirely understand how tornadoes form, they do have a good idea about the conditions that cause them to develop.
Twisters have touched down on all continents except Antarctica, but certain locations on the planet are more likely to experience tornadoes than others. Most tornadoes occur in the so-called Tornado Alley, the tornado-prone region of the United States, from Texas north into Kansas and the surrounding states of the Great Plains region.
If a tornado is to form an area must have the three ingredients necessary: a lot of warm, moist air close to the ground; atmospheric instability, a condition that promotes the vertical movement of air; and clashing air fronts that act to propel moist air upward.
Scientists believe that if the two opposing winds move at different speeds, the air in between them will rotate around a horizontal axis. If one end of the horizontal air column gets caught in the supercell's updraft, it will tilt vertically, forming a funnel cloud.
The continuous upward energy of the supercell elongates the funnel cloud, and causes its spin to tighten and speed up, similar to the way ice skaters spin faster when their arms are pulled close to their bodies.
It is now high season for tornadoes in Sweden, but it is difficult to say how many occur each year. Tornadoes are often short-lived, and therefore difficult to observe.
“There are usually about a dozen tornadoes in Sweden each year”, says Camilla Albertsen, a meteorologist at the Norwegian Weather Service.
“Powerful tornadoes in Scandinavia can lift rooftops or cars, but usually only topple a few trees."