  We have used an innovative tuneable filter technique to carry out a search
for the variability signatures of meterological processes in the atmospheres of
two nearby brown dwarfs. We find no evidence for variability in the L-type
brown dwarf DENIS-PJ1228-1547 in an observations spanning approximately half a
rotation period (3 hours), and evidence for variability in the M-type brown
dwarf LP 944-20 in multiple observations spanning approximately one third of a
rotation period (1.5 hours).
