I can't find the answer anywhere on the internet. Except for that it can be seen as a whole-half scale with the sixth note left out. However this explanation doesn't satisfy my desire for an official name. Does anyone know what this scale is called?
You can look at it as mode of the Romanian major scale which if built on C results in the scale:
C Db E F# G A Bb
If you started on the G you would get the scale you describe:
G A Bb C Db E F#
It's not really a common scale so there's not really an exact name. If you needed to call it something I would go with melodic minor 5b due to the fact it is one note off from the melodic minor scale, but just calling it the 5th mode of Romanian major scale would also work.