May 21 - July 30
Analysis of Tornadogenesis Failure Using Rapid-Scan Data from the Atmospheric Imaging Radar
Kyle Pittman, Andrew Mahre, David Bodine, and Casey Griffin
What is already known:
- Prior studies have proposed theories on how tornadoes form (tornadogenesis) that have yet to be proven.
- High temporal resolution radar has helped better understand the evolution of tornadoes spawned by supercells, and helped better understand the physical mechanisms responsible for tornadogenesis.
- Many supercells appear capable of tornado production, yet fail to do so.
- High temporal resolution radar analysis of tornadogenesis failure has yet to be done.
What this study adds:
- Observations using high temporal resolution radar were taken of a suspected tornadogenesis failure case (from a supercell).
- Detailed analysis of the rear flank downdraft and mesocyclone showed a lack of vertical continuity in storm features, which may be responsible for the failure of tornadogenesis.
- This study lays the ground work for future analysis to be done on additional tornadogenesis failure cases, in order to compare observations/mechanisms that may be responsible.
Abstract:
Tornadogenesis in supercell thunderstorms has been a heavily studied topic by the atmospheric science community for several decades. However, the reasons why some supercells produce tornadoes, while others in similar environments and with similar characteristics do not, remains poorly understood. For this study, tornadogenesis failure is defined as a supercell appearing capable of tornado production, both visually and by meeting a vertically contiguous differential velocity (ΔV) threshold, without producing a sustained tornado. Data from a supercell that appeared capable of tornadogenesis (but which failed to produce a sustained tornado) was collected by the Atmospheric Imaging Radar (the AIR, a high temporal resolution radar) near Denver, CO on 21 May 2014. These data were examined to explore the mechanisms of tornadogenesis failure within supercell thunderstorms. Analysis was performed on the rear-flank downdraft (RFD) region and mesocyclone, as previous work highlights the importance of these supercell features in tornadogenesis. Preliminary results have found a lack of vertical continuity in rotation between the lowest level of data analyzed (100 m AGL), and heights aloft (> 500 m AGL). A relative maximum in DV occurred approximately 100 m AGL (0.5° in elevation on the radar) around the time of suspected tornadogenesis failure; this contrasts with weaker ΔV at elevations aloft. Additionally, the RFD produced by the Denver Supercell had a peak in intensity aloft (between 2.5 and 3 km in height) just prior to the time of tornadogenesis failure, while simultaneously experiencing a relative minimum in intensity in the layer between the ground and 1 km.