There is an "improved version" of japanese written in english, where the 's' in 'tsu' is dropped and readers are expected to remember that 'tu' is pronounced 'tsu' (and 'si' is pronounced 'shi' and so on). This probably won't filter back to english/american dictionaries cuz of how long ago the word was inducted into our common parlance. I can see typoes happening where the 's' is lost from 'tsunami' I also suspect there are some people who can't pronounce 'tsu' no matter how hard they try just like some people can't make the Vulcan Salute.
Strange thing is