Meteorological overview of the devastating 27 april 2011 tornado outbreak

The article presents a meteorological overview of the tornado super outbreak of April 27, 2011, illustrating some unique features of three distinct episodes of tornadoes over this 24-h period. A mesoscale convective system (MCS) that evolved to an intense quasi-linear convective system (QLCS) during the early morning hours, a smaller QLCS over northern AL during the midday hours, and widespread discrete supercell storms during the afternoon evening time period. In addition, an east-to-west oriented thermal boundary developed during the late morning and early afternoon hours over northern AL owing to the cold outflow air produced by a midday QLCS, followed by persistent clouds and rain showers that maintained this cool air mass over northern AL, while relatively high insolation heated much of central AL.