A strong new warming phase is getting closer, and is set to begin in 10 days! The final power and the later effects are still under discussion. So far, the weather model calculations were good.
In case you are not familiar with this process, we ancourage you to chek our tutorial post, that explains WHAT IS THE POLAR VORTEX AND WHAT IS ITS SIGNIFICANCE.
The polar vortex is currently under pressure from a medium power wave-2 pattern. This “attack” pattern will slowly weaken, making way for the near record-strong wave-1 pattern to take over. The number of the wave tells us how many “highs” are pressing against the polar vortex (low). On the image (weatheriscool.com) below we can see the current ongoing wave 2 nearly gone, as the Atlantic high has weakened.
The polar vortex will have little time to catch some breath. Its bad luck will continue, as a strong wave-1 pattern will start to emerge in just a few days, yet again pressing strongly towards the polar vortex. This time from just one side.
The 16-day ensemble forecast shows the strength of the stratospheric jet stream around 30km altitude. Notice the short break in the weakening trend, as the wave-2 attack ends and the vortex catches some air. Then we see the weakening continue, as the strong wave-1 pattern emerges, seen above. There are now ensemble members starting to show the reversal of the stratospheric jet stream (red color), which would qualify this warming event as a technical Sudden Stratospheric Warming (SSW) event.
By November 30th, a new warming phase will start over the Eurasian sector. It is forecast to escalate fast, emerging much stronger than the current warming phase. We forecasted additional warming phases over one week ago, due to sharp pressure differences and atmospheric wave-breaking in the higher levels.
The warming in the stratosphere usually comes from the top down. Energy from the lower levels near the ground is deflected upwards and reaches the top of the stratosphere. It is then amplified, releasing the thermal energy, warming the upper stratospheric layers and slowly propagating downwards, embedding and weakening the polar vortex in the process. Fueled by the energy of the atmospheric wave breaking, the warming pulse will quickly gain strength, raising temperatures in the middle-stratosphere over Siberia by up to 40°C in just a few days!
The temperatures at the 10mb level (~30km altitude) are forecast to rise from -55°C to -10°C. That temperature at this level is over 35°C above the 30-year average! The wave 1 pattern attack from the pacific will weaken in the meantime, but a new high will be building over the Asian sector, along with the warming. The warming will weaken the polar vortex significantly, but a strong new pressure wave would also be needed along the warming, to ensure the final collapse of the polar vortex.
We also proudly present you our own full 3D analysis. This shows the stratosphere, from 14-48km altitude. The 3D mass in blue, is the core, hearth, of the polar vortex. The red mass is the warmer air, usually found on the edges of the highest stratospheric layers. We can see over time, how the polar vortex is trying to grow but is actually being pushed aside by the powerful warming wave.
What all this means for our weather? Well, a collapsed vortex always greatly increases the chances for winter weather towards Europe and CONUS. A lot depends on how the existing pressure pattern looks, while the effects from the stratosphere come crashing down on us. In some cases, the effects can be partially “deflected” and we don’t feel much of a change in our daily weather. But in most cases, the effects can have a major influence on the distribution of weather systems across the hemisphere. The graphical example below shows the average temperature anomaly 0-30 days after a major warming event. We can see the main cooling effects are across Eurasia and the United States.
We will keep you updated on any important further development, as this situation is just starting to unfold, with many weeks of monitoring and observing ahead!
But while you wait for more updates, make sure to check out the latest long-range winter forecasts, from various models around the world:
WINTER 2019/2020 MODEL FORECAST
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