Classic and HP mini-supercells in southeast Oregon and southwest Idaho on 3 May 2009

During the early afternoon hours of 3 May 2010, several severe thunderstorms occurred in southeast Oregon and southwest Idaho. One of these storms displayed characteristics of a classic mini-supercell, including a pronounced occluding mesocyclone, movement to the right of the mean wind, large hail as indicated by a three-body scatter spike, rear-flank downdraft, and low cloud-top. Another storm displayed characteristics of an HP mini-supercell, including rotation, kidney-bean shape, right-movement, and low cloud-top. These storms formed in advance of a strong negatively-tilted short wave trough and associated 25 m s-1 (50 kt) jet at 500 mb. Closest NAM and GFS Bufr soundings for the time and location of the storms showed approximately 1300 J kg-1 CAPE, 65 m2 s-2 0-3 km SREH, and a bulk Richardson number of approximately 18. In addition, they indicated that the CCL would be around 975 m (3200 ft) AGL. This is notably lower than the average CCL for this climatic region (Hurlbut and Parker, 2006, SLS Preprints). Plan-view displays of 0-3 km SREH from the NAM indicated a maximum of about 200 m2 s-2 in the area of the storms, which is more typical of the low level shear one would expect in an environment with multiple supercells. These storms will be described in detail as examples of unusual storms, and to raise awareness of their occurrence in this climatic region.