High Plains presentation now online

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 sector 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