Over the past couple of weeks, I've thrown together a spatial environment climatology of supercell environments based on 0000 UTC North American Regional Reanalysis data. A "supercell" environment is defined here as MLCAPE >= 1,500 J/kg, 0-6km BWD >= 35 kts., 0-3km SRH >= 150 J/kg, all in the presence of MLCIN >= -25 J/kg (a small capping inversion). This equates to an old 'fixed' Supercell Composite Parameter (SCP) calculation of around two. Remember that a majority of right-moving supercells are associated with SCP values greater than a value of one (Thompson et al. 2003). Basically, if a storm is present in this environment, it has a statistically significant chance of being a supercell.
The spatial anomaly plots shown in the link below are all plotting the frequency of the particular threshold discussed above. Keep in mind that environments favorable for supercells can (and often do) arise outside of +/- 3 hours around 0000 UTC. Thus, this environment climatology is biased towards diurnally driven convective environments. Black 'freckles' on the anomaly maps indicate a statistically significant (α=.05) difference between that particular year and the 1980-2011 climatology. Before you ask, yes, I have made similar images for individual months, but I have not made an online repository for them yet. Please send any questions to my e-mail, or comment below.