Andy Fischer of NOAA/AWC Kansas City and I submitted a paper to the 12th Annual High Plains Conference (Hays, Kansas Sept. 4-5), “Significant Nighttime Tornadoes in 2008 Associated with Relatively Stable Low-level Conditions”. I could not attend, so Andy presented the paper. Andy’s presentation is now online in PDF format here.

The presentation focused on the setting and environment with the Beloit-Jewell-Belleville tornadic supercell in northern Kansas on 29 May 2008, and the Salina-Chapman-Manhattan supercell in central/northern Kansas on 11 June 2008. Both storms were associated with unusually large CIN for such intense tornadoes. MLCIN from lowest 100-mb mixed-layer lifted parcels was large for both events, probably between -120 and -170 J/kg, depending on the computer model used. This seems very large for significant tornadoes based on my database study from a 2004 paper in Weather and Forecasting.

What we found was that 0-1 km storm-relative helicity (SRH) was also unusually large (500-800 m2/s2) for these two supercell tornado events, particularly on 29 May. When combined with moderate total CAPE (at least 2000 J/kg) and strong deep shear (at least 55-60 kts), it appears that the environments for these events supported and enhanced intense mesocyclones to the extent that they were able to overcome the stable near-ground layer to generate tornadoes. Andy’s presentation suggests that these combined ingredients (unusually large SRH, strong deep shear, at least moderate CAPE) can definitely support tornadoes in large CIN _warm secto_r environments, and should be noted carefully by meteorologists, even when CIN suggests that an environment is not strongly surface-based. I’m hoping to post some addiitonal material on these events in the near future.

- Jon Davies 10/5/08