The phrase "altered suddenly" is correct and usable in written English.
It can be used to describe a change that occurs abruptly or unexpectedly.
Example: "The weather altered suddenly, catching everyone off guard with a torrential downpour."
Alternatives: "changed abruptly" or "shifted unexpectedly."
Montgomery's alter ego suddenly and violently crossed over from fantasy to real life.
Ana flees the tram and takes refuge in the city's Botanical Garden, but the way she perceives the world has altered radically: "And suddenly, uneasily, she felt she had fallen into a trap.
Mr. Okada's ideas about the book were suddenly altered, however, after the 2011 earthquake and subsequent tsunami that caused the meltdowns at the nuclear power plant in Fukushima.
Farmer scrutinizes F.A.A. and Norad records to provide irrefragable evidence that a day after a Sept. 17 White House briefing, both agencies suddenly altered their chronologies to produce a coherent timeline and story that "fit together nicely with the account provided publicly by Deputy Defense Secretary Wolfowitz and Vice President Cheney".
Mr. Mnookin traces out all these separate threads (with the footnotes of a true scholar), even venturing away from the tangle long enough to explain how scientists are trained to think about causation and how profoundly this measured approach is bound to infuriate a distraught parent with a suddenly altered child.
To find out, researchers trained big brown bats (Eptesicus fuscus) to fly through a dense maze of dangling plastic chains, then suddenly altered the maze path.
During the crisis these norms of communication were suddenly altered by changes in the already complex functions of different actors, often creating tension – for example between the chief minister and the governor.
Positive selection is known to occur when the environment that an organism inhabits is suddenly altered, as is the case across recent human history.
When that situation suddenly alters its a shock".
It is not however a substance that dramatically changes someone's intrinsic personality traits, suddenly altering someone from being mild mannered to criminalistics.
