Severe Weather in the USA

  • This tornado hit Colorado on 31 May 2010. Credit: Helen Rossington, Senior Forecaster at MeteoGroup

    On Thursday 3 April 2014, the Storm Prediction Center, part of NOAA, issued a warning for moderate risk of severe thunderstorms and tornadoes. Credit: NOAA

  • Severe Weather in the USA
    03.04.2014 16:02

    North America is no stranger to extreme weather and with the peak tornado season just starting it is no surprise that there have been severe weather warnings in effect for parts of the USA.

    On Thursday 3rd April parts of Louisiana, Arkansas, Missouri, Illinois, the extreme south of Indiana, Kentucky, Tennessee and Mississippi had a moderate risk of severe thunderstorms and tornadoes; and there were reports of a tornado in University City, St Louis State in Missouri. This tornado coincided with the 40th anniversary of the Super Outbreak in 1974, which saw 148 tornadoes tear through 13 states as well as Ontario, Canada, and was one of the USA’s worst tornado outbreak.

    The severe thunderstorms on Thursday brought very strong, gusty winds in excess of 70mph, as well as very heavy rain. In just two hours Whiteman in Missouri recorded 80.5mm (3.2 inches) whilst Sedalia, also in Missouri, recorded 55.4mm (2.2 inches).

    The risk of severe thunderstorms will shift eastwards on Friday 4th April, across parts of the Ohio Valley, the Appalachians, the Gulf Coast and Mississippi Valley, before the risk of severe thunderstorms diminishes over the weekend.

    Tornado activity varies from year to year and this is clear when comparing the total number of tornadoes for each year between 2010 and 2013. In 2010 a total of 1,543 tornadoes were recorded, with a total of 1,691 tornadoes recorded in 2011. In contrast, 2012 and 2013 were significantly quieter years with 939 tornadoes recorded in 2012 and 908 recorded in 2013.

    One factor that perhaps had some affect on suppressing the frequency and intensity of tornadoes in 2012, is that many of the states in ‘Tornado Alley’ were in the clutches of severe drought. This lack of moisture is thought to have had a knock-on effect on the atmosphere leading to insufficient instability to produce tornadoes.

    During the tornado season in 2013, Oklahoma endured a deadly couple of weeks during the last two weeks of May, which resulted in 34 fatalities. This was 62% of the total number of fatalities recorded across the whole of North America in 2013.

    By: Gemma Plumb