First they occlude it far too rapidly then it’s a cold front again

I will be the first to admit I have never been a weather forecaster and I haven’t studied in detail the development of the low that is forecast to affect Ireland on Wednesday. But I have seen a lot of weather charts in my time and I am familiar with the Norwegian Cyclone Model and to my mind the following show very little continuity with the frontal system associated with the low itself. You’ll notice that there’s a tongue of warm air (>546 dam thickness) that’s bulging up with the T+60 frame, that combined with the fact that the low has deepened from 998 to 985 hPa strongly suggests that the low is still developing and has not reached full maturity, but as you can see its already well occluded, so much so that by T+96 it’s fully occluded lying across Iberia. But then magically in the T+120 chart, which was produced at the same time as the T+96 chart, the fully occluded front suddenly turns back into a cold front as far north as Denmark. Perhaps the occlusion was always a cold front as it does seem to have quite a cold (<546 dam) trough following on behind it. I think one of the problems these days is that detailed NWP doesn’t always fit with the classical model, and although Wednesday’s low may turn out to have not much of a warm sector, I can’t for the life of me understand why they occluded it so rapidly in their forecast charts.

Courtesy UKMO
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