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A gigantic tornado hit a suburb of Oklahoma City in the USA.
Dr John Roberts, Fellow, Institution of Structural Engineers, said:
“All structures are designed against forces from wind – it is one of the three basic types of loading. For tall buildings it is often the dominant loading condition.
“In the UK engineers design buildings to safely survive storm gusts that range from about 85mph in London to about 120mph in the Western Isles. These speeds are predicted to occur for a three second duration once every 50 years (on average) and are called the “50 year gust speed”. The most serious (type EF5) tornadoes, such as those seen in the USA, will impose a force about 10 times as high as this. No ordinary building can survive such extreme conditions.
“The primary damage is probably caused by suction forces in the tornado, which will lift off roofs, or even whole buildings. Once the roof is detached from the walls below total destruction instantly follows. Heavyweight, below-ground concrete basements can be designed to survive even EF5 tornadoes, notwithstanding the loss of a building above. However they are expensive and are not currently mandatory, even in the “tornado alley” area of the Great Plains where the majority of the extreme events occur.”
Professor David Schultz, Professor of Synoptic Meteorology, University of Manchester, said:
“Tornadoes are unfortunately to be expected in this area of the US at this time of year. [Compared to the 1999 Oklahoma tornado, which was of similar magnitude, yesterday’s tornado sadly led to a greater number of deaths]*. This is partly because of the time of day it occurred – at around 3pm, parents were out and about picking up children from school and some children were still in class. Because people were less likely to be near a television or listening to a radio, they might not have heard warnings and therefore unfortunately might not have been able to take precautions. In 1999 the tornado hit at around 7pm, when most people were sitting down to dinner or watching the evening news, which would have been reporting live on the track of the tornado. Sheltering within their homes with their families would have been easier. Clearly, the time of day that the tornado hits can affect people’s ability to be prepared.
“In the US, the National Weather Service issues outlooks days in advance of anticipated severe weather. The outlooks highlight regions of the country that face the risk of tornadoes, large hail, strong winds, and lightning. With possible tornadoes three to six hours away, watches are issued that highlight portions of a state or two. Tornado warnings are issued when the threat of tornadoes is imminent. Warnings often appear tens of minutes before the tornadoes hit. In the case of large and violent tornadoes, such warnings can be quite accurate. Weaker tornadoes sometimes may happen without warning. Research within the National Severe Storms Laboratory and the Storm Prediction Center aims to improve the tornado warning process, giving more lead time to the public.”
Dr John Marsham, School of Earth and Environment, University of Leeds, said:
“We do not yet know the full details of this particular event and it is impossible to attribute any one event to climate change. Tornadoes are too small to be explicitly represented in climate models. However, research shows that in much of the USA climate change is likely to lead to increase in the frequency of severe storms, and tornadoes form as a result of severe storms. Climate change therefore may well increase tornadoes, but the effects are expected to be regionally varying and much remains uncertain.”
Dr Andrew Russell, Lecturer in Climate Change, Brunel University, said:
“It is unclear whether tornadoes will become more likely as our climate changes because computer climate models don’t have the power (i.e. high enough resolution) to represent tornadoes. So you can’t just go through climate model data and count the tornadoes that it thinks will occur. It is possible, though, to look at the changes in the larger scale conditions that usually result in tornadoes, but this also gives us a unclear picture: whilst the increased warmth and moisture predicted by climate models will mean more energy would be available to developing tornadoes, the climate projections also shown a decrease in the occurrence of the wind patterns that are needed to form tornadoes. Nonetheless, there is some good evidence showing that reducing greenhouse gas emissions now will reduce the risk of more severe storms and tornadoes in the future.”
Dr Andrew Barrett, Department of Meteorology, University of Reading (commenting on the frequency and strength of tornadoes), said:
“Tornadoes are quite common in the Great Plains in May, averaging about 3-4 per day (often in clusters) – but not usually as strong as this one, and not usually in urban areas. Only 2% of tornadoes in the USA reach EF4 status (scale EF0 to EF5), with winds over 165mph.
“Tornados can occur in many places across the globe, but tornado alley of the Central Plains of the US is most famous. Central Plains in US is ‘Tornado Alley’ because it sees frequent collisions of warm, moist air from the south and cold air from further north and has no major east-west mountain range to block air flow between these two air masses.
“Moore, Oklahoma has been hit by significant tornadoes four times in the last 15 years (1999, 2003, 2010 and yesterday) including most intense storm ever with winds of 317 mph. The size of the tornado was not unprecedented, but at larger end of scales (widths vary from: 100m – 3 km).”
Dr Suzanne Gray, Senior Lecturer in Weather Systems, Department of Meteorology, University of Reading (commenting on climate change and tornadoes), said:
“Tornados are too small scale for current climate models to simulate, so it is not possible to say very much about how strength and occurrence might alter under climate change. But climate change means warmer temperatures and more moisture and that is providing more energy for the types of storms that produce tornadoes in a warmer climate.”
Dr Pete Inness, Lecturer and Senior Research Fellow, Department of Meteorology, University of Reading (commenting on tornadoes in the UK), said:
“The geography of the US High Plains is unique in creating the perfect environment for tornado formation. In the UK we simply don’t have the right set of circumstances to generate the intense storms in which big tornadoes form.
“According to the UK Tornado and Storm Research Organisation (TORRO) the UK experiences 30-40 tornadoes per year, although these are all far weaker and shorter lived than their US equivalents and most cause little or no damage to property. Recent occurrences include a small tornado in Oxfordshire in May 2012 which was tracked using Doppler radar by researchers at the University of Reading.
“In July 2005 a tornado hit Birmingham where damage to trees, houses and cars was widespread across an area to the south-east of the city centre. This was one of the few UK tornadoes to cause significant damage (estimated at 40 million pounds) and 19 people were injured.”
Further notes on tornadoes, from the University of Reading:
What is a tornado?
A rotating column of air usually accompanied by a funnel-shaped downward extension of a thunder cloud and having winds whirling destructively at speeds of up to 300 miles per hour.
Dr Matt Watson, Lecturer in Natural Hazards, University of Bristol, said:
“Springtime in Oklahoma is pretty much prime time and place for tornadoes, therefore sadly this is not particularly unusual. It is virtually impossible to attribute single events like this to climate change.”
Professor Bill McGuire, Professor of Geophysical & Climate Hazards, UCL, said:
“While there is no discernible upward trend in the number or strength of tornadoes in the US, I would not be surprised to see more in the way of the most powerful tornadoes as the world continues to warm. As climate change tightens its grip, extreme weather of all types is likely to be the order of the day.”
* Media reports at the time these quotes were sent out erroneously gave figures of around 90 for the death toll. These have since been revised down to 24, which is less than the 1999 tornado.