Hey Jim, my roommates both lived in Joplin, one is now back in Joplin volunteering and meeting with his girlfriend. The devastation is something he says the TV cannot get without seeing it personally. There houses are completely gone. He has asked me to check out some forecasts for him as the weather gets bad and showing him a skew-t, I came across the storm from the other day:http://weather.uwyo.edu/cgi-bin/sounding?region=naconf&TYPE=GIF%3ASKEWT&YEAR=2011&MONTH=05&FROM=2112&TO=2500&STNM=72440The CAPE is some of the highest I have seen. (And I assume the CAPE over 4400 is an error but 2700 is insane)
Tornadoes have been reported in environments with a wide range of CAPE, including low cape environments (<500 J/kg). 4000 is high, but there have been events with CAPE > 5000 J/kg. CAPE is great, but the ingredients for supercells also include storm-relative helicity and deep-layer shear. See http://radar.weather.gov/images/eax/web/presentations/severeweather/Supercell_environments_Davies_2007.pptfor more info.