In this first post, I will directly link the stratosphere analyses, from the FU Berlin, Institute of Meteorology. These analyses are sourced by ECMWF 12z runs.

Up in the stratosphere, there is a phenomenon called the Polar Vortex. It affects the Troposphere and the weather patterns and circulation over the entire North Hemisphere. The same phenomenon is also present on the south pole. Some say that the AO can be a indicator of the polar vortex, but that is not really true, since the main activity happens much higher than where AO is based (1000hpa). AO can basically reflect the changes, but the polar vortex changes cant be forecasted by just looking at the AO.

The most important things to monitor, are the geopotential height and the temperature. Stratosphere is very "tall", so we must look at several different layers.

Lower stratosphere:

50hpa


30hpa



Mid stratosphere:

10hpa


5hpa



Upper stratosphere:

3hpa


1hpa


And I will also add the Zonal mean sections for the northern hemisphere.

Temperature:


Zonal wind:


This is just an analyse post. I will write something about the polar vortex in the next days.

Best regards.

Be real, be yourself, be unique, be true, be honest, be humble, be happy. :)

Andrej Flis / Marquis Andras

As I promised, here is something about the polar vortex.

It is basically a large scale cyclone, situated over both poles. It is "based" in the upper troposphere and the entire stratosphere. it is the strongest in winter (unless a Sudden Stratospheric Warming occurs), when the temperature gradients are also the strongest.

This is the official definition:

"This is a phenomenon that occurs during the polar winter in which stratospheric air moves in a circular motion, with an area of relatively still air in its centre. The temperature in the vortex is approximately -80°C, which assists in the formation of polar stratospheric clouds. In the Arctic, the vortex is asymmetric and typically features a trough (an elongated area of low pressure) over eastern North America. It is important to note that the polar vortex is not a surface pattern. It tends to be well expressed at upper levels of the atmosphere (that is, above about five kilometers)."

I've put the words in bold, to point out, that AO (Arctic Oscillation) cannot be used for referring to Polar Vortex. Changes in the Polar Vortex do reflect in the AO (with quite some lag), till some extent of course, but that is about it.

Here is a Earth circulation schematic. Polar vortex affects basically the entire hemisphere. It is not really the same as a normal cyclone, because the air in the centre is descending. Kinda like a Hurricane.



For the polar vortex to "function" or spin normally, there must be allot of cold present. Warmth ( I mean higher than normal temperatures, not actual warmth), and of course consequently higher geopotential heights, disrupt the Polar vortex and can stop the circulation or even reverse it.

The warming and disruption is currently occuring at higher levels of stratosphere. It can lead to a SSW, but things are not certain yet about this top stratosphere warming. But, as the warm air surrounds the vortex, and penetrates into the core, the vortex can weaken dramatically at that level, and even stop or reverse.



We are going to witness a large "heat" wave 1 induced warming, that will disrupt the stratosphere for the first time since last winter. These waves usually occurs from blockings and heat flux, or a High in the upper stratosphere.



This wave that will break into the upper stratosphere, will be large enough to give a forecast reversal of mean zonal mean winds at the upper levels of the stratosphere. The vortex will probably not break up completely. It will be on the edge of existence, but I think that we will need another wave and subsequent warming to break the vortex.



The warming will propagate down to the 10 hPa level, but it is insufficient to give us a SSW at the moment.



But, the forecasts are very encouraging, because a strong Pacific High (ridge) is forecasted, and will have some effects on the vortex positioning in the troposphere. It is possible, that this Pacific ridge builds into a block over Pacific, which would be a good condition for another heat flux wave, from the troposphere into stratosphere, for an eventual SSW. That would be a real game changer, and a very decent winter could happen if the SSW occurs. The problem is still the time and the Lag effect (delay). It takes some time for these large scale processes to reflect down to the lower levels of atmosphere, troposphere.

This is all for now. Somewhere in the next few days, I will post something about the Sudden Stratospheric Warming (SSW), and its effects on the overall patterns, connection with the Quasi-Biennial Oscillation (QBO), and so on,... So I will develop this topic in sequences and not all at once, because that would be too much data and information at once. :)

Best regards.

Be real, be yourself, be unique, be true, be honest, be humble, be happy. :)

Andrej Flis / Marquis Andras