Hi Brent,
Welcome to this forum 
There have been several discussions regarding the Tempest distance to the hub and improving the signal strength. Use the search feature magnifying glass at the top of this page to find them.
A new topic began recently which specifically targets your question with references to some of the discussions:
A difference between a Sky and a Tempest is that the Tempest includes solar panels and a battery surrounding the antenna. For my long distance Sky it has no batteries or solar panels between the antenna and the hub because the Sky battery using the solar power accessory stores its battery below the Sky. I believe that the transmitter power and the antenna are the same design in both.
If you could get your hands on a Sky with a solar power accessory then I would be confident that it will get better reception. People on this forum have sometimes tried to get a Sky from others because many people who now have a Tempest may have an old Sky in their spares. They are no longer in production.
Another thought I have had if my Skys all fail and I need to use a Tempest at longer distance is to pull it apart and install an extension or move the antenna outside from the solar panels or move the solar panels. Which of course would invalidate the warranty etc.
Another thought is to make a simplified parabolic reflector behind both the hub and the Tempest. If you only need to improve it slightly this may be enough. There are pictures on the forum of dismantled Tempest and hub which show the antenna as a vertical wire. The internet has lots of images of people doing that to improve their wifi etc.
And you can see the results updated every minute (I think) on the status page of your rssi values.
Also make sure the hub is flat side facing the Tempest. To be very tidy and minimalistic perhaps just a sheet of metal or metal tape attached to the back side of the hub. There is a comment some where about which side of the hub the antenna is on, which they worked out by pulling it apart.
good luck, cheers Ian