weaker

Something is happening in the north and we’ve been saying it for days. Forecasts pointed to a huge sudden stratospheric warming during the last week of November. I said ‘huge’ and it is not a rhetorical device: it is normally very difficult to know what consequences such a warming will have; but being so big, meteorologists they already speculate with a complete destabilization of the polar vortex. And the strange thing about all this is not that there is such a big “sudden stratospheric warming.” That’s relatively normal. The strange thing is that we are facing a very precocious one. Surely, before the earliest of the entire record. And that has set off all the alarms. What is the polar vortex? But let’s start at the beginning: the ‘polar vortex’ is a stream of strong winds (west → east) that revolves around the large reserves of cold air found above the planet’s poles. It is formed in the stratosphere; that is, at about 16-48 kilometers high. On a metaphorical (or ‘journalistic’ if you push me) level, the polar vortex is what the cold contains at the pole. Logic tells us that, in summer, the vortex is reduced to a minimum and, although it is true that we have never seen it disappear, it becomes so weak that it loses any influence over the time of the hemisphere. But in winter the situation changes and it does so radically. Very often, during the winter the vortex grows and, although “usually a solitary creature“and harmless, it is common for it to overflow and end up affecting the rest of the hemisphere. That is what it seems we are going to see these weeks. And what is sudden stratospheric warming?? To understand this process well, it is good to remember that the atmosphere is a “lasagna of air layers” and each of them follows its own logic. That is, they function quite differently and independently; but never completely independent. This is what happens between the air circulation in the troposphere (the one closest to the surface) and the circulation in the stratosphere (the layer directly above): they are related, yes; but, in substance, each one goes their own way. During the “sudden stratospheric warming“, a part of the troposphere warms rapidly and, as a consequence, invades the stratosphere, causing a profound alteration of the circulation at high altitude. That is, for a few days, everything turns upside down. Okay, so what’s going to happen? The data begins to indicate that the countdown has already been activated. As they pointed out from Meteored“a record has been recorded in the speed of the zonal wind of the polar vortex, this would be weaker than ever on those dates.” That is to say, we have just found the first sign that warming is already underway. The problem is that, as Víctor González pointed out“the ease of predicting sudden stratospheric warming in the medium term contrasts greatly with the difficulty of anticipating its consequences.” Hence, we already know with almost absolute certainty that something is going to happen in the stratosphere of the north pole, but it is not clear what is going to happen. And we know nothing of its consequences? Not for now. What’s more, it seems likely that the consequences would not be seen until mid-December. For now, the experts will have “monitor the alteration of the stratospheric polar vortex and then monitor its propagation to lower levels, finally observing how the tropospheric circulation and the polar jet may behave.” This is very meticulous work, but very necessary. We already know that this type of event is related to historic cold waves and, in that case, we better be prepared. Image | Severe Weather In Xataka | The last hope of winter in Spain is desperate, but increasingly possible: the breaking of the polar vortex