Bitcoin is back, according to longtime bull Tom Lee.

Despite the cryptocurrency's drop in early Friday trading — a symptom of worries around the legitimacy of another digital currency called tether — it's going higher, and may even be in a bull market already, Lee tells CNBC.

"Last year was a terrible year for crypto, a massive bear market, and we published a piece this week just highlighting … 11 signs that historically only take place in a bull market. So I think the evidence is mounting that there's a bull market," Lee, who is managing partner and head of research at Fundstrat Global Advisors, said Thursday on "Futures Now."

Of the 11 signs that the "crypto winter" is over, Lee's top bullish drivers for bitcoin have to do with blockchain, technical indicators and trading volumes.

The first sign came in January, when Lee's team noticed that trading volumes on the blockchain — a technology some use to buy and sell bitcoin — turned positive year over year. That boost was helped by turmoil in Venezuela and Turkey, where people losing faith in their countries' currencies may have turned to bitcoin as an alternative, Lee explained.

"Just taking those two countries, they're close to 30% of the increase in on-chain activity, so it's meaningful," he said. "People are saying, 'Look, I don't trust using these local currencies. I don't trust the banks. I'm going to start using bitcoin.' And that's what's causing on-chain volume to really take off."

The second sign came in April, when bitcoin closed above its 200-day moving average, a widely accepted technical indicator of bullish momentum.

The third sign stemmed from a Fundstrat survey of over-the-counter brokers, who Lee said are "really important in terms of how institutional investors trade crypto." They told the firm that activity levels based on number of clients saw a 60% to 70% increase, and that trading per client surged.

"I think you're seeing signs that fundamentals are improving, technicals are improving, and now there's real activity by, essentially, crypto hodlers," Lee said, using an industry term that refers to people who hold cryptocurrencies rather than trading or selling them.

Lee's eight other bullish signs include shrinking supply; a swing to the positive in Fundstrat's Bitcoin Misery Index; consensus among "original" bitcoin bulls that the bottom has been put in for bitcoin; and a recent "golden cross" for bitcoin, or when the 50-day moving average overtakes the 200-day.

All this, he said, goes to show that bitcoin's not done climbing, and that these catalysts are "likely" to drive it to new all-time highs "around" 2020.

Lee, who predicted a 2019 bull market for bitcoin in March, added that the cryptocurrency's standard deviation from the S&P 500 — which this year is about 2.5 — could also help push it higher.

"One thing to keep in mind is whenever the S&P has made a big move, ... it's almost always led to a big move in crypto later in the year," he said. "So I think … a 2.5 standard deviation move for bitcoin would take it to $14,000. I'm not saying that's where it's going to go, but that's the magnitude of move that would be a catch-up."

Bitcoin traded in a wide range Friday on account of weakness in the broader cryptocurrency market, settling in roughly the $5,100 per coin range. Lee noted in a Friday call with CNBC that tether's issues don't have "much effect on bitcoin," since most people are "long tether because [they] don't want to be long bitcoin."