High activity in the polar vortex indicates an increased chance of cold waves affecting several areas of the northern hemisphere.

Arab Weather - Weather experts at the Arab Weather Regional Center said that the latest analyses from computer simulations to monitor the upper layers of the atmosphere above the Arctic Circle indicate that the stratospheric polar vortex has been growing stronger and more cohesive since the beginning of November (which is the main distributor of cold air masses in the northern hemisphere). The vortex is expected to grow stronger and more cohesive during the coming period, especially towards the end of the month, which increases the chances of cold waves affecting several regions of the northern hemisphere.

Rapid growth of the stratospheric polar vortex and cooling of polar air masses over the Arctic

In this context, it is expected, God willing, that the polar vortex will grow rapidly during the rest of the month, as temperatures at an altitude of 30 km above sea level will drop to about 80 degrees below zero, which means that polar air masses will intensify and expand over the North Pole. The air in this region is very dry and cold, and this cooling leads to a large temperature difference between the pole and areas located at lower latitudes. As the stratosphere continues to cool, the speed of the westerly winds surrounding the polar masses increases.

The strong winds form a circular system known as the stratospheric polar vortex, which traps cold air inland and separates the polar regions from the temperate regions. As fall continues into winter, the polar vortex becomes more stable and stronger, increasing the temperature difference between the poles and other regions.

Increasing chances of cold waves affecting several regions of the Northern Hemisphere

Due to the expected high activity in the polar vortex, a large ripple is expected in the polar jet stream, a strong and fast air current that moves from west to east in the upper atmosphere, typically 10 to 15 km above the Earth's surface. This current forms over the Arctic and Antarctic regions as a result of temperature differences between cold air at the poles and warmer air in the tropics.

As a result, very cold polar air masses are expected to rush towards North America, Canada, and northern Europe, specifically Scandinavia and northern Asia, especially Russia and the surrounding countries. This will cause strong cold waves accompanied by heavy snowfall and a sharp drop in temperatures amidst very cold weather in the mentioned areas.

For those interested and specialists: How is the strength of the stratospheric polar vortex determined?

The strength of the Arctic vortex is determined by several key factors, and its strength is usually measured by the strength of the winds within and around it. This is done by measuring the speeds of zonal winds (moving from west to east) around the Arctic Circle at 60 degrees latitude. One of the most important factors that influences the strength of the polar vortex is the "polar jet stream," a stream of fast winds that forms at high altitudes and surrounds the vortex.

When winds in the jet stream are strong, they strengthen the polar vortex, which helps trap cold air within the polar region. In this case, the vortex remains stationary and stable, which means cold weather stays confined to northern regions. But when the jet stream weakens, the vortex becomes distorted, allowing cold air to rush south toward warmer regions, causing temperatures to drop in parts of Europe, North America and Asia.

Temperatures in the stratosphere play an important role in determining the strength of the polar vortex.

Temperatures in the stratosphere (at altitudes of 10 to 50 kilometers) are another indicator of the strength of the polar vortex. When temperatures in this layer drop significantly, it helps stabilize the polar vortex, making it stronger and more rigid. But sometimes, a phenomenon called “sudden stratospheric warming” occurs, where temperatures rise unexpectedly, causing the polar vortex to weaken or even break up into smaller vortices. This leads to major weather disruptions, as cold waves rush south of the vortex, causing significant temperature drops in some areas.

Importance of the Polar Vortex (AO) Index

Scientists measure the strength of the polar vortex using an index called the Arctic Oscillation (AO), a numerical indicator that helps describe air pressure and weather patterns over the North Pole. When the AO is in its positive phase, the polar vortex is strong and cohesive, keeping cold air trapped in the north. When it is in its negative phase, the vortex is weaker, allowing cold air to rush south.

And God knows best.