Is it me or does the 564 dm line in the 1000-500 hPa thickness chart just doesn’t seem to want to retreat southward this Autumn? I would have thought that by now it would be just off the north African coast rather that across southern France. Despite numerous cold fronts in the last few weeks trying to push colder air down into Europe the old 564 thickness line – which many people use to distinguish a warm spell of summer weather – doesn’t seem to want to budge at the moment, and remains aligned, and seemingly fixed at latitude 45° north.
Repercussions for the rest of the autumn
If this continues to be the case as the northern hemisphere continues to cool as it heads towards winter, you might expect the thermal contrast between 45° and 65° north to be that much greater than average, which in turn would tighten the jet stream and encourage more cyclonic development and greater zonality. Well that seems to be what’s happening at the moment at any rate, and is not an unusual occurrence around the autumn equinox. It will be interesting to see just how stormy the run up to Christmas will be this year.