382 2 April 2017 Louisiana Tornado Outbreak

Monday, 8 January 2018
Exhibit Hall 3 (ACC) (Austin, Texas)
Robert Megnia, NWS, Lake Charles, LA; and T. W. Humphrey and J. Rackley

On 2 April 2017 an area of low pressure near the western Gulf Coast resulted in one of the largest tornado outbreaks in Louisiana since 1950. The day saw a total of 22 tornadoes, six of which were classified as significant (EF2+). This extreme event resulted in five casualties, two of which were fatal, and millions of dollars worth of damage. A climatology of individual tornado days dating back to 1950 ranked this event first for total number of tornadoes (22) in a day and second for number of significant (EF2+) tornadoes (6) in a day. To assess the overall impact of this outbreak, the Destruction Potential Index (DPI) was used to compare both the overall number and strength of tornadoes to previous events. The 2 April 2017 event had the highest DPI for the state of Louisiana since 1950. Comparisons to tornado days on a regional scale also highlight the significance of this event. We compared the synoptic conditions of 2 April 2017 to a series of 23 member synoptic scale composites of past tornado days with six or more tornadoes. These composites highlighted the synoptic ingredients which may have contributed to the severity of this event. The conditions for the 2 April 2017 event had distinct differences from the composited events, one being the position of the surface low which had a more favorable location for the development of both strong low level helicity and bulk shear. These two parameters were determined to be major contributing factors to the development of the 22 confirmed tornadoes on this day. Understanding the ingredients which contributed to this significant event may be used by operational forecasters to better anticipate the severity of future convective events within this region.
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