Notes on Scottsbluff, Nebraska, Tornadoes, 27 June 1955

Beebe, Robert G.

doi:10.1175/1520-0477-40.3.109

Cited by 5 publications

(3 citation statements)

References 2 publications

(8 reference statements)

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“…In some cases, z o could not Ј be determined because e values measured at the surface were all larger than those observed on the proximity sounding. mented by van Tassell (1955) and Beebe (1959) near the Scottsbluff, Nebraska, tornado may be the most difficult observations to reconcile. The observations were reportedly within 1 km of the tornado, to its south.…”

Section: F Reconciliation Of Findings With Past Observationsmentioning

confidence: 94%

“…Observations were made on several occasions from the 1950s through the 1970s of low e and w air at the surface within RFDs (e.g., van Tassell 1955;Beebe 1959;Ward 1961;Browning and Ludlam 1962;Browning and Donaldson 1963;Charba and Sasaki 1971;Lemon 1976;Nelson 1977;Brandes 1977a;Barnes 1978a,b). A major finding of this research, as presented in sections 3a and 3b, is that cold temperatures and low e / w RFD air are associated with tornadogenesis failure.…”

Section: F Reconciliation Of Findings With Past Observationsmentioning

confidence: 99%

“…However, direct observations within hook echoes and RFDs have been scarce. A few observations have been mentioned by van Tassell (1955), Beebe (1959), Garrett and Rockney (1962), Browning and Ludlam (1962), Charba and Sasaki (1971), Lemon (1976), Barnes (1978a,b), Knupp (1980), andBluestein (1983). Thermodynamic retrievals have been performed (e.g., Brandes 1984a;Hane and Ray 1985), but small-scale details cannot be resolved, buoyancy fields often are noisy, and data within the surface layer, which are perhaps most important, are unavailable.…”

Section: Introductionmentioning

confidence: 99%

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Direct Surface Thermodynamic Observations within the Rear-Flank Downdrafts of Nontornadic and Tornadic Supercells

2002

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Despite the long-surmised importance of the hook echo and rear-flank downdraft (RFD) in tornadogenesis, only a paucity of direct observations have been obtained at the surface within hook echoes and RFDs. In this paper, in situ surface observations within hook echoes and RFDs are analyzed. These ''mobile mesonet'' data have unprecedented horizontal spatial resolution and were obtained from the Verifications of the Origins of Rotation in Tornadoes Experiment (VORTEX) and additional field experiments conducted since the conclusion of VORTEX. The surface thermodynamic characteristics of hook echoes and RFDs associated with tornadic and nontornadic supercells are investigated to address whether certain types of hook echoes and RFDs are favorable (or unfavorable) for tornadogenesis.Tornadogenesis is more likely and tornado intensity and longevity increase as the surface buoyancy, potential buoyancy (as measured by the convective available potential energy), and equivalent potential temperature in the RFD increase, and as the convective inhibition associated with RFD parcels at the surface decreases. It is hypothesized that evaporative cooling and entrainment of midlevel potentially cold air may play smaller roles in the development of RFDs associated with tornadic supercells compared to nontornadic supercells. Furthermore, baroclinity at the surface within the hook echo is not a necessary condition for tornadogenesis. It also will be shown that environments characterized by high boundary layer relative humidity (and low cloud base) may be more conducive to RFDs associated with relatively high buoyancy than environments characterized by low boundary layer relative humidity (and high cloud base).

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Section: F Reconciliation Of Findings With Past Observationsmentioning

confidence: 94%