Well, that was only partially right.
Indeed, northern Illinois (where I grew up and was focusing my efforts) did NOT see another strong tornado, or really any severe weather at all--just some rumbles of thunder as the front came through in in the areas of heavy rain that proceeded it. But look at the storm reports from yesterday:
|Fig 1 -- SPC storm reports for Dec. 31, 2010.|
|Fig 2--SPC storm reports for January 7th, 2010.|
|Fig 3 -- SPC storm reports for January 8th, 2010.|
|Fig 4 -- HPC surface objective analysis from 12Z, Dec. 31, 2010.|
|Fig 5 -- HPC Surface analysis for 12Z, Jan 8, 2010.|
|Fig 6 -- HPC surface objective analysis for 00Z, Jan. 1, 2011.|
|Fig 7 -- HPC objective analysis for 00Z, Jan. 9, 2008.|
So we can reasonably see why there was the similarity in Mississippi on both days. So why didn't we see reports in Missouri on both days? My guess is in the differences in the movement and orientation of the more northerly half of the system. First, in figure 5 above, we see that the "cold" front from northern Illinois down through central Missouri is marked as a stationary front at 12Z on Jan. 8th. In fact, this frontal boundary was around since the day before:
|Fig 8 -- HPC Surface objective analysis for 00Z, Jan. 8, 2008.|
|Fig 9 -- KILX sounding from 00Z, Jan 8, 2008.|
|Fig 10 -- Incomplete sounding from KILX at 12Z, Jan 8th, 2008.|
Still, my point is that convection on January 7th in the Saint Louis area probably helped stabilize the atmosphere enough to limit any further convection in that area on January 8th. However, in our event yesterday, there was no convection the previous day and as such everything happened at the same time.
I wanted to compare upper air charts as well (since they are remarkably different) for these two events, but this is already a long post and apparently Blogger has an image limit of 10 per post that I was not aware of. So, I'll do another quick post tomorrow to finish this up and compare the upper air patterns. For a brief preview of that, though the depth and placement of the troughs are vastly different, the upper-air winds over our areas of interest are very similar. So in terms of shear and any other sort of forcing due to jet streak divergence aloft and whatnot, things are actually rather similar, even though the overall patterns themselves are rather different.
But anyhow, that was a look at how two wintertime severe weather outbreaks were actually very similar in terms of their structure and timing (at least at the surface). I want to especially thank Tim Supinie for suggesting that I look into this. Since there was no severe weather yesterday in northern Illinois I had originally not thought to revisit the comparison, but this look back does highlight some nice similarities between the two events.