A detailed analysis of an extremely long-tracked supercell

A significant tornado outbreak occurred on 12 March 2006 across the central United States. This outbreak resulted in many long-lived tornadic supercells. An unusually long-tracked supercell produced many of the day's tornadoes, including one with a documented 106 km (66 mile) path length. Radar indicates that this supercell tracks from northern Oklahoma and southeastern Kansas in the morning, across Missouri during the afternoon and early evening, across Illinois during the mid to late evening, into Indiana during the late evening, before finally dissipating in southern Michigan. With a path nearly 1300 km long and duration exceeding 15 h, this is likely the longest lived supercell on record.

During the day and evening of 12 March 2006, a strong mid/upper level trough with a 50 m/s mid level jet moved east across the Central and Southern Plains. Meanwhile, a strong southwesterly low level jet exceeding 30 m/s veered from the Mid-Mississippi Valley toward the Ohio Valley. A surface front that extended from a surface low over Eastern Colorado across Oklahoma to the Mid-Mississippi Valley lifted north as a warm front in response to the strong pressure falls extending from the Central Plains toward the Great Lakes. The surface low tracked eastward across northern Kansas and into Missouri. Increasing low level convergence in the vicinity of the surface low and extending southward along the prefrontal trough/dry line was the focus for thunderstorm initiation during the afternoon across eastern Kansas and Western Missouri. Surface dewpoints reached the upper 60s F as far north as southern Missouri and Illinois. Steep mid-level lapse rates combined with this moisture to produce CAPE AOA 2000 J/kg in the warm sector. Deep layer shear was more than sufficient for supercells and the strong low level jet contributed to large hodographs which were supportive of long track tornadoes.

Single Doppler data from several radar sites will be used to document the storm reflectivity and velocity structures through the storm's entirety. Time-height rotational velocity (Vr) traces will be used to show the characteristics of the circulations and illustrate the differences between the tornadic and non tornadic vortices. Comparisons will be made between those circulations that resulted in tornado formation and those that did not.