Consider the vowel in a word like "know". The way I pronounce it sounds maybe like /nøʉ/ to me. But other Brits oftentimes think I have a foreign accent, so I don't know about that. And I am sure I've heard people say /no:/ as well.
But what I'm interested in knowing about is the pronunciation /nuɔ/.
It seems to appear in Jamaica (I say so because of Lee Perry's pronunciations in an old recording of the song "I Man Free"). And the Wikipedia page on Jamaican Patois gives this example:
/if kau no did nuo au im tɹuotuol tan im udn tʃaans pieɹsiid/ ('If the cow knew that his throat wasn't capable of swallowing a pear seed, he wouldn't have swallowed it')
(And by the way I thought it notable that
no are not homophonous in this variety of English).
I will make another assertion, but this one is not backed up by the Wikipedia page on Mackem or Geordie: The same sound change has happened in the North East of England, and appears to be accompanied by a similar process that's /eɪ/ → /iə̯/ here and in Jamaica alike.
By my intuition, the "semivowel half" of a diphthong is usually a high vowel, like /ɪ̯/ or /ʊ̯/. By my intuition, diphthongs that involve a glidey thing that's qualitatively like /ɔ/ or /ə/ are cross-linguistically very rare. So has there been some kind of analysis on how and why this has turned up around twice, and in at least two varieties of English separately? Or have I misunderstood something?