That looks pretty narrow and vaulted. The convention generally used on this forum for intermolar width is the distance between the narrowest points on the lingual edges of the first molars. However, different sources use different landmarks and it's most important to be consistent to track changes. I started with a 34mm intermolar width and found it challenging to correctly posture my tongue.
Watch starting at 2:19 of https://www.youtube.com/watch?v=26KBKhaieSE
Listen to 24:27 - 25:50 (or to end) of https://www.orthotown.com/blog/post/9121/episode-21-dr-john-graham
You may want to check out a CBCT from an airway-focused orthodontist.