Terminal reports "Your disk space is critically low"

All of a sudden Terminal is reporting that my disk space is critical. I have over 700GB of 2TB available...

This is the message:

But this can't been.

I also have 40GB of RAM and this is not under pressure either.

I have three tabs open in Terminal. Basically one is decompressing recovery zips that size around 20GB each. The other tab is doing du -s on folders and the other tab is performing other directory tasks.

Any idea why this is coming up and how to get rid of it, as low disk usage does not appear to be the issue.