Updated: Oklahoma tornado – experts respond

May_20,_2013_Moore,_Oklahoma_tornadoUpdated: A Huge tornado has devastated the US state of Oklahoma killing at least 24 people and injuring many more.

Earlier reports indicated more than 90 fatalities, however this number was revised downward.

Our colleagues at the UK SMC collected the following expert commentary. Feel free to use these quotes in your reporting. If you would like to contact a New Zealand expert, please contact the SMC (04 499 5476; smc@sciencemediacentre.co.nz).

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.”

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.”

From the AusSMC:

Professor Dale Dominey-Howes, Natural Hazards and disaster management expert at the University of New South Wales, comments:

“Today’s tornado in Oklahoma is at the upper end of the magnitude scale of tornados. Given its size and the wide area of impact, searching for and rescuing survivors will stretch emergency services. Further, treating the injured and reuniting families will be extremely challenging. The response and recovery effort will require both State and US Federal resources and important questions must be asked about the effectiveness of early warnings and the building standards of property that are constructed in places where tornados like this occur.”

Dr Todd Lane, ARC Future Fellow, School of Earth Sciences, The University of Melbourne, comments:

“Tornadoes form below a class of severe thunderstorms known as supercells. Supercells feature intense upward moving columns of air that rotate, as the wind near the surface is drawn into those columns it begins to rotate and forms the tornado vortex. The damage attributed to tornadoes is caused by the strong winds in the vortex and flying debris.

“Oklahoma sits within an area of the United States commonly referred to as ‘tornado alley’ – this area is amongst the most frequent locations of tornado occurrence in the world. At this time of year, the warm and moist air from the Gulf of Mexico and cool and dry air from above the Rocky Mountains come together to make tornado alley the perfect environment to spawn supercells and tornadoes.

“Preliminary reports of damage from the Oklahoma tornado suggest it was of EF-4 intensity, which is the second highest intensity rating. EF-4 tornadoes have wind gusts between about 265 and 320 kilometres per hour.”