I take it you are referring to Part I of this amazing poem, when the ship is driven by storms towards the South Pole and before the Mariner kills the albatross. The storm seems to emerge out of nowhere, interspersed as it is between what is going on in the church during the wedding and the compelling, mesmerizing and riveting account of the Mariner. See how the storm is described in his words:
"And now the STORM-BLAST came, and he
Was tyrannous and strong:
He struck with his o'ertaking wings,
And chased us south along.
With sloping masts and dipping prow,
As who pursued with yell and blow
Still treads the shadow of his foe,
And forward bends his head,
The ship drove fast, loud roared the blast,
And southward aye we fled."
Note how Coleridge uses personification to compare the ship to a person leaning forward as he flees a pursuing enemy. Clearly, the stormy blast that has caught up the ship completely overpowers the ship and the crew's efforts to steer it, leading it on into a strange and mystical world full of icebergs.
The description of the storm appears in lines 41–50 of "The Rime of the Ancient Mariner." The mariner describes the storm that drove the ship toward the South Pole by personifying it as a winged creature and by personifying the motion of the ship before the storm. The mariner calls the storm "he" and says that the storm "struck with his o'ertaking wings." This calls forth the image of a huge bird of prey or possibly even a winged dragon that chases the ship southward. The adjectives "tyrannous" and "strong" also personify the storm as a cruel master that compels obedience.
The mariner then uses figurative language to describe how the ship moved in front of the storm. He likens the ship to a person who is ducking his head and bending forward to escape the "yell and blow" of an enemy who is pursuing him. Despite these efforts, the fleeing person remains in the pursuer's shadow. This represents the ship's complete inability to escape the storm; the ship and crew were completely at the mercy of the driving wind.
The mariner says that the storm blast roared loudly and drove the ship at high speed to the south. The other literal description the mariner provides is that the storm caused the masts of the ship to slope and the prow to dip into the waves.
The mariner uses some literal descriptions of the storm but also describes it figuratively as a cruel master, a winged creature, and a dreaded enemy.