Apple - How to connect to a specific BSSID via Terminal?
You can use
airport -A=ssid -BSSID=bssidname -password=password
To find out the BSSID
/System/Library/PrivateFrameworks/Apple80211.framework/Versions/A/Resources/airport -s
/System/Library/PrivateFrameworks/Apple80211.framework/Versions/A/Resources/airport -A
no longer is a supported option, but the airport-bssid tool is good for seeing a list and connecting to a bssid manually.
https://github.com/deekayw0n/airport-bssid
see the README.md for usage.