Some forecasters have now called the system a "bomb cyclone", capable of generating 40 to 50 foot waves and causing severe flooding in parts of the UK.
According to the Met Office, a bomb cyclone - and bombogenesis, the phenomenon that causes it - are not official terms. Both actually refer to a phenomenon called explosive cyclogenesis.
And it happens to Storm Dennis.
Met Office spokesperson and meteorologist Oli Claydon told WalesOnline: " [Explosive cyclogenesis] this is mainly when a low pressure system deepens rapidly, where it lowers its central pressure by 24 millibars in 24 hours, and it is an indication that it is getting quite hard-hitting, fairly severe. "
Dennis was classified as a bomb cyclone on Thursday morning - the product of an explosive cyclogenesis - after the storm's central pressure dropped 46 millibars in just 24 hours, according to AccuWeather.
"Additional reinforcement could put Dennis in the running for one of the most intense North Atlantic storms on record, depending on the drop in central storm pressure," said AccuWeather meteorologist Courtney Spamer.
The lower the central pressure of a storm, the more extreme the storm's output can be.
But in the case of Storm Dennis, rapid intensification occurs at sea, far from the coast of the United Kingdom.
This means it is very unlikely to hit a record high when it hits the UK starting on Saturday.
Weather maps show the central low-pressure system measuring at 974 on Friday, said Claydon, who then quickly deepens to a lower number, before increasing again when Dennis approaches the coast.
For this reason, the Met Office said that the impacts of the storm should not be as severe as those of Storm Ciara.
But they will always have a punch.
Mr. Claydon said: " [Storm Dennis] does not deepen explosively when it reaches us, but there will always be strong winds and lots of heavy rain. "
“With very strong winds and this kind of low pressure, we will see significant wave heights on the coast.
"And with many flood warnings from environmental agencies, people have to pay attention to them. Take the advice of the emergency services if they say stay away, "he said.
The storm is expected to arrive in Wales on Saturday, with the strongest winds developing in the afternoon and evening.
A lull is expected overnight, before speeds increase again on Sunday morning.
Gusts of 50 mph are expected inland, with speeds of up to 60 to 70 mph around the coast, particularly to the west and south.
Strong winds will sometimes be accompanied by heavy rain, leading to particularly bad driving conditions.
Delays and cancellations of road, air, rail and ferry transport are expected.
Met Office chief meteorologist Steve Willington said: "Following the Ciara storm last weekend and further episodes of rain this week, the ground is already saturated in places. floods, including property damage and a life threatening hazard from fast flowing flood waters. "
Amber rain warnings are in place for much of Wales between 12:00 p.m. Saturday and 3:00 p.m. Sunday.
Meanwhile, the yellow wind warnings will start a little earlier at 10 a.m. on Saturday and will last until 12 a.m. on Sunday.