Deadly tornado strikes Moore, Oklahoma

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  • The May 22nd tornado captured on a mobile phone from a person in Newcastle, Oklahoma. (Credit: reddit.com/r/weather)

    56 years of tornado tracks across the US. Interestingly is the near-absence of tornadoes in the Appalachian Mountain region in the eastern United States. (Credit: NOAA)

    Radar images of the 1999, 2003 and 2013 tornado. (Credit: NOAA)

  • Deadly tornado strikes Moore, Oklahoma
    25.05.2013 14:38

    Background

     

    On 20th May, meteorological conditions contrived to form a deadly tornado that brought chaos to the town of Moore and surrounding areas in central Oklahoma. Instability in the atmosphere coupled with strong wind shear led to the favourable atmospheric conditions for tornado formation. At 2.40pm local time on May 22nd, a tornado touched down north-east of Moore as an EF0 (the lowest grade of tornado on the Enhanced Fujita Scale-used to measure tornado strength). By the time it reached Moore, it had damaged bridges, farms and killed livestock. By around 3pm, meteorologists from the National Weather Service were sending out tornado warnings that a developing tornado was en route towards Oklahoma City and Moore. 

    As the tornado passed through rural areas, it had a strength of EF2-EF3. As it moved into Moore, it had reached up to EF4 strength. As it passed by an elementary school, winds of between 200-210mph were recorded, thus making it an EF5 (maximum strength) for a short time. Storm chasers estimated the tornado to have reached 1.3 miles in diameter. As the tornado passed on and began to dissipate, the true scale of the destruction was realised.


    Publicity

    Tornadoes strike many parts of the United States and often the chance of striking a certain area is small. Frighteningly though, a tornado of similar magnitude struck the same area in May 1999, the radar images of each can be seen in Figure 3 on the left. The ’99 tornado caused the fatalities of 36 people then.

    Within minutes of the tornado track being identified, warnings from forecasters were sent out. Credit has been given to these forecasters for identifying the track and giving good warning. Publicity of the tornado grew massively with news teams and storm chasers taking pictures that were beamed all over the world. News of the tragic deaths reverberated across the country with immeasurable sympathy going to the victims. Miraculous stories of how people survived were strewn across the internet. One such story involved a woman who took shelter in the safe in the bank she worked in. When she emerged after the tornado had pass, the safe was the only structure left standing from the bank. Indeed, the difference between safety and total destruction was just the width of a road (Figure 3, for example). 

    Analysis of the supercell that produced the Moore tornado was analysed. Radar images of the past 3 tornadoes show a striking resemblance in the ‘hook’ like structure that forms. Some people were able to take striking pictures of the tornado from their back gardens as it flew past their towns. 

     

    Reactions

     

    As the fallout of the extreme weather takes its toll, further disruption can be expected. Tornado season, it is obvious,  is well underway. Somewhat unusual is the number of tornadoes identified (274 since last Monday) compared to the average (491 through until 20th May). Regarding the cost of the disaster, insurance companies have paid out more in the past 5 years than ever before with thunderstorm related claims. With hurricane season around the corner, people of the southern US are bracing themselves for further severe weather. 

     

    By: Seán Penston