An aircraft penetration through a rear-flank downdraft: Revisting an old case

A somewhat-famous early NSSL dual-Doppler radar case study occurred on 8 June 1974. On that day an outbreak of tornadoes began in central Oklahoma and continued into eastern and northeastern parts of the state. The first storm of the day, the Oklahoma City tornadic storm, moved across the metro area, producing three tornadoes. The events were captured by NSSL's two 10-cm Doppler radars and other sensors, and data analyses were the subject of a number of conference papers and formal publications. One part of the dataset, instrumented aircraft data from the University of Wyoming King Air, has never been fully exploited. During one very special pass, the aircraft, flying just below cloud base (~800 m AGL), approached the storm right-rear flank from behind, penetrated the rear-flank downdraft and gust front, sampled the storm inflow, circled back, and re-penetrated the gust front and rear-flank downdraft a second time. All this took place while flying close to a tornado in progress along the gust front and dodging a developing tornado beneath a prominent wall cloud. Unfortunately, the lack of level, straight flight prevented the recorded wind data from being useful. However, the pressure, temperature, dew-point temperature, and rate-of-climb parameters are available for analysis. This paper will show those data and locate the aircraft data with respect to dual-Doppler analysis. Such analyses allow comments to be made about the above-ground thermodynamic character of the rear-flank downdraft and other storm features. Thoughts will be shared about the importance of data of this type during the upcoming VORTEX2 field program.