Crude oil prices just posted their longest losing streak in three years, registering six straight weeks of declines, and one veteran oil watcher says there could be much more volatility ahead.

Tom Kloza, co-founder of the Oil Price Information Service, told CNBC's "Futures Now" this week that oil prices have been so volatile that a slump to $50, or even a spike above $100 could not be completely ruled out.

"If we had an oil [volatility index] it would be incredibly volatile over the period" of the last 17 months, he said. West Texas Intermediate crude hit a year-to-date peak above $74 in early July, a 25 percent increase from its February trough below $60.

A move of that severity is not unheard of in commodity markets. From the middle to end of 2008, during the height of the financial crisis, crude oil tanked 77 percent. During the more recent slump from mid-2015 to early 2016, prices tumbled 56 percent.

Crude oil's first move could be higher over the next few weeks, according to Kloza.

"For the next few weeks what you really have to watch for WTI are the Cushing inventories," said Kloza. "They're about 21 million barrels compared to numbers that are closer to 55 or 65 million barrels in the last couple of years, so you could have a squeeze between now and when the September WTI contract expires."

Kloza says tighter inventories at Cushing, Oklahoma, a major crude hub, could push the price of WTI back above $70 in coming weeks, a level it has not seen this month.

Politics, both domestic and international, could then quickly take oil lower heading into November, says Kloza. The ongoing war of words between the U.S. and Iran remaining center stage.

It's "very, very bumpy. Very unpredictable and the president is a great reason for that, the campaign against Iran is a great reason for that," he said, calling President Donald Trump a "meddler-in-chief" for his more active role in moving oil prices.

Under pressure over rising gas prices, Trump in July called on the Organization of Petroleum Exporting Countries to bring down oil prices. He is reportedly also considering the sale of some of the U.S.'s emergency oil supplies to deflate crude prices, according to a report in Reuters.

U.S. sanctions against Iranian oil are due to go back into effect on Nov. 4. That could take more than a million barrels of Iranian oil out of global circulation, which could then push oil prices higher again.