The US-born winger, who this season was called up for his first involvement in the Scotland squad, signed from Ulster Rugby in 2011, going on to make 14 appearances and notching two tries in his first season with the Warriors.
He leads the Warriors current try tally table with fellow winger DTH van der Merwe.
Tommy said: “I said when I joined Glasgow that it was a little like coming home because of the family connection and I’m really settled here. The way the squad and team are developing is a massive factor in staying on because the players and coaches here do believe that we’re building towards something special.
“It’s an exciting place to be at the moment and even though the results don’t always go your way, we know we’re headed in the right direction.
“The game against Edinburgh this Friday at Scotstoun is massive for us as a club, not just because of the intensity of the rivalry, but for our season and for our position in the league it’s vital we do everything we can to pick up points.
“I came here to play regular rugby and to get that call-up to the Scotland squad was a real vindication of the hard work though I know, given the talent that is now in the Warriors squad, that I have to keep at it and keep trying to get better.”
Tommy was born and raised in Nashville, Tennessee before moving to Northern Ireland via a spell in Dubai, where his father was based for work. He qualifies for Scotland through his mother, who was born in Glasgow.