AROME has a much deeper trough than the low res 12Z models.
And on its back side a much larger height rise.
All the ensembles that have the cold solution together with the GFSpara6Z from yesterday have deep troughs that force a stronger more westerly height rise.
It could be as simple as this.
Low res models underestimate strength of trough. Trough is actually deeper and pushes low heights further south. Heights behind rise more sharply. This causes a pressure rise further west over the UK and keeps the tilt more negitive.
Originally Posted by: Quantum