Posted by Chris on 4/16/2009, 9:42 pm, in reply to "EHI just went ballistic - where's the PDS?"

http://www.spc.noaa.gov/exper/mesoanalysis/s6/index2.html Composite Indices > 3km EHI or 1km EHI Info: http://www.stormtrack.org/library/forecast/ehi.htm http://www.srh.noaa.gov/bna/research/svrlist.htm http://www.spc.noaa.gov/exper/mesoanalysis/help/help_ehi.html - "Energy-Helicity Index: The basic premise behind the EHI (Energy-Helicity Index) is that storm rotation should be maximized when CAPE is large and SRH is large. 0-1-km EHI values greater than 1-2 have been associated with significant tornadoes in supercells." And the really complicated math: http://en.wikipedia.org/wiki/Helicity_(fluid_mechanics)