It is working exacly as it is design to.
The cable modem is not ON your network, it is all by its lonesome like it should be.


You have pegged the downtime to bad weather.
Next time it happens, go to the cable status logs, grab screen shots (or wget pulls) od the messages concerning communication failures.

Actually, you might want to script a wget to pull them on a schedule.

They only keep the last 'x' entries. You would then write a script to dedupe the overlaps.

Then when you realize there is a LOT more downtime than your interactive usage notices, you can use the logs as proof to your cable company of how bad the service is, and force them to do a bit of rewiring.