The phrase "a powerful undercurrent" is correct and usable in written English.
It can be used to describe a strong, often hidden influence or feeling that affects a situation or context.
Example: "The discussion seemed lighthearted, but there was a powerful undercurrent of tension among the participants."
Alternatives: "a strong current" or "a significant undertone".
This gives a powerful undercurrent to the drama.
Political analysts here acknowledge that nationalism remains a powerful undercurrent in Serbian politics.
It was a powerful undercurrent throughout much of the Middle Ages, shaping numerous movements in that period.
Brutal, unblinking and ruthlessly honest, with a powerful undercurrent of black comedy, it quickly earned an exalted place in American cinema.
Leaders here know that anti-foreign nationalism, shaped by the state education system and mass media, is a powerful undercurrent in Chinese society.
One could say much the same about the crude contempt for Barack Obama that has become a powerful undercurrent in Republican politics over the last seven years.
He received compensation, but it was a pitiful recompense for what's become a lifetime of chronic ill-health, and there is a clear and powerful undercurrent of anger in Landy and his work that is borne of his father's experience.
Saint Etienne arrived perfectly pitched between the then cutting-edge shimmering beats of clubland and sepia-tinted nostalgia for pop's lost innocence, with an indefinable but powerful undercurrent of melancholic longing.
And a powerful thematic undercurrent of his oratory and prose was race.
$21. Sandor Marai's lustrous novel about an adulterous affair in turn-of-the-century Austria-Hungary could be taken for a jeweled antique, with its setting on a vast Hungarian estate and in Vienna's imperial establishment, its powerful undercurrent of suspense and its elegantly wrought armature of moral and metaphysical argument.
The book's real distinction, though, is its stubborn, powerful undercurrent of regret, mostly felt by Sabich but also, to a lesser degree, by everybody else in this murky world, where even the bright light of the law can't show people, or their desperate acts, as they truly are.
