Evolution and Impacts of the 27 April 2011 Early Morning Quasi-Linear Convective System and Meso-Vortex Tornadoes in the Central Tennessee Valley
Kula, Andy ; Latimer, Stephen ; Knupp, Dr. K; Coleman, Dr. T

The largest tornado outbreak in the NWS Huntsville Weather and Forecast Office s County Warning Area began during the early morning hours of 27 April 2011 with the first of three successive waves of tornadic thunderstorms. A quasi-linear convective system and an embedded mesoscale convective vortex were responsible for no fewer than 15 tornadoes producing EF-1 and EF-2 damage (subject to further adjustment) that struck northern Alabama and southern middle Tennessee during the early morning hours of the 27th. The tornadoes struck between 0901 UTC and 1218 UTC, in some cases very close to one another in both space and time. In addition to the tornadoes, widespread straight-line winds of 50 to 70 mph caused additional significant damage. The Huntsville WFO issued 21 tornado warnings and eight severe thunderstorm warnings during this initial wave of storms. The damage to communication and power infrastructure were significant and likely impacted the ability of the public to receive crucial tornado warnings during a second (late morning to early afternoon) and then third wave (from the mid-afternoon through late evening) of severe storms.

In addition to an overview of the tornadoes, this presentation will include a review of the synoptic and near storm environments, a discussion of the numerical model forecasts, and some examples of the radar imagery of this intriguing system and warning challenges it presented.