[Geysers] Long-term periodicities at Steamboat (& elsewhere)?

[Davis, Brian L.]

Looking at the Steamboat temperature log here:

http://volcanoes.usgs.gov/yvo/activity/monitoring/norris/steamboat.php

I noticed something I'd never known before (I know, there's a LOT I don't know) - Steamboat seems to have a nicely periodic 4.5 day cycle (most easily seen in the monthly graph). That surprised me, and got me thinking about what could do that, as well as when in the cycle a major is most likely to happen. Is there any information on this?

While on the subject of long-term cycles, what others are known? I realize Giant hot periods might fit in this category, but I'm not sure what else might? Annual cycles might be related to seasonality, but certainly this doesn't explain things like a 4.5 day cycle.

-- 
Brian Davis