I think I've found the key factor. So the difference between the ARPEGE, JMA and the good GEFS vs GFS and the ICON is the position of the upper level low in the southern north sea. We want it as far west as possible, the further west it ends up being, the weaker the heights are over the UK later as the atlantic tries to move in, that allows the lower heights from the NE to better separate the azors part from the greenland part.
To me the UKMO6Z is about half way between the GFS and the JMA solution.
HARMONIE is closer to the JMA solution.
Interestingly enough the GFS fed WRF is slightly further towards JMA than the GFS is.
Originally Posted by: Quantum