ALTHOUGH Monday’s tornado may have seemed unusual, the Metservice says the Eastern Bay is more susceptible to tornados than other areas of the country.
“The Eastern Bay is more prone to experiencing tornadoes because of the formation of the countryside,” said meteorologist April Clark. “For a tornado to form there must be thunderstorms present within a front which cause an updraft. Below that, there must be low-level wind shear (wind blowing in different directions). The two together create a corkscrew effect leading to a tornado.”
The destruction caused by the tornado could have been a lot worse as Monday’s tornado reached only the lowest level on the Fujita scale.
“This tornado was rated at F1 on the scale. In New Zealand we rarely get F2 and only very occasionally do we get F3,” said Miss Clark. “To put it into context, America’s tornados would rate at F4 or F5.”
An F1 rated tornado usually has a wind speed of between 117 to 180 kmh and is around 16 to 50 metres across at its widest point.
These tornados usually cause the type of damage seen in Ohope with roofs peeling off, vehicles pushed off the road and destruction of garages.
Many Ohope residents believed they were looking at a water spout which turned into a tornado as it hit land, but Miss Clark said this is not the case.
“Water spouts and tornados are very different; a water spout cannot come onto land as it needs the warm water to survive. This is simply a tornado which started at sea. From far away they can look very similar, but what people were seeing is cloud pulling down to the ocean, not water being pulled up.”
Miss Clark also said it was typical of tornados to cause very localised destruction.
“While it may seem to people that the tornado was ‘jumping homes’, you have to be directly in the path of the tornado to experience any damage. Most tornadoes here are only about 10 metres wide, and if you are outside that 10m you won’t be affected. They also don’t follow a linear pattern which is why it might seem it missed homes.”