The Euro took a huge move south at 00z and the GGEM has been all over the place. I wouldn’t call that consistent.
I would argue actually that the GFS OP has been more consistent.
I think it has to do with that upper level low in the Gulf of Alaska honestly. It shunts the ridge out west pretty significantly and prevents the southern wave from digging enough.
GFS south and weaker from 18z
At 500mb the set up is a lot more similar to the 12z with the upper level ridge out west shunted east and the PV oriented more towards the east.
The effect looks to make everything more progressive.
Also that vorticity in the Gulf of Alaska is shunting the upper level ridge on the west coast. Grrrr
A number of issues on this run I think will cause the SLP to be southeast of the 00z.
Maybe models ingested some new info?
One thing I’ve noticed is that the trend today has been to bring the leading wave further south, which may be the issue here.
Euro showing the same signs.
Pretty interesting differences at H5 on the 12z GFS. Higher heights out ahead but low is further south at 500, causing the surface low pressure to be further south.