"intensely strong" is correct and can be used in written English.
It describes something that is extremely strong or powerful. Example: The wind blew intensely strong, nearly knocking me off my feet.
It was an intensely strong experience.
But beneath the mild surface is an intensely strong current of religion.
The writer discusses the alienating effect the de Menils' art careers and their intensely strong marriage had on their 5 children.
And male silkworm moths are excited by infinitesimal traces of the female sex pheromone, even in the presence of odours that are intensely strong to humans.
In many ways, these still-life images are overpowered by the intensely strong faces watching from the other side of the gallery.
To combat the headaches, he began chewing a substance called naswar, a powdery bright-green tobacco and herb mix, intensely strong, that numbs the entire body.
The fire is burning intensely under strong northerly winds.
Republicans have struggled in this election with two powerful and competing impulses: to hammer a president they dislike intensely with a strong indictment of his record, but to be restrained enough to win over independent voters, who generally like Mr. Obama.
It was rated TV-14 for intensely suggestive dialogue (D), strong coarse language (L) and intense violence (V).
It is intensely deformed, with a strong differentiated fabric composed of alternating millimeter-scale laminae of quartz and sheet silicates, formed by solution-redeposition processes (Schmidt and Platt 2018).
Serious tea drinkers seem to gravitate to stronger, more intensely flavored blends, according to tea experts.
