In recent weather forecasts, a concise detail has attracted special attention from experts: The rare strong disruption of the polar vortex since the beginning of December.
On satellite maps, the "cold circle" that was once stable in the Arctic was no longer compact, but was stretched and distorted towards the Asian - European continent. For atmospheric scientists, this is an early sign that cold air could move to medium latitude in an unusual way.
Typically, strong turmoil of extreme cyclones often occurs in January or February, when winter has reached its peak. Early December is considered the "warming up" period, where cold spells come and go quickly, interspersed with warm air. This year, that order is at risk of being disrupted.
Forecast models show a rapid increase in the upper air mass, accompanied by unusually warm areas at an altitude of about 30km - a "push" strong enough to push the cold air mass deep into the south.
A severe tornado can be imagined as a giant rotation containing cold air. When rotated steadily and steadily, the cold will "come" in the Arctic. But if the child spins around early and strongly, each cold air mass will slide down, causing unexpected cold spells in North America, Europe and East Asia.
In fact, history has recorded "rule- breaking" winters associated with extreme turmoil. In early 2013, North America experienced record cold spells. At the end of February 2018, Europe suffered a "monster from the East" when the cold air in Siberia overflowed and stationed for many days.
The common point of these events is the accumulation of signals from the upper atmosphere before the Earth's surface clearly felt the cold. This time, those signals appeared much earlier.
If this scenario happens, this winter may no longer follow the familiar rhythm of "cooling to medium - warming up - turning cold again". Instead, there are heat shocks: Rapid to deep, persistent, interspersed with strong fluctuations.
Meteorological experts emphasize that extreme cyclone turmoil does not necessarily mean that there will be snowstorms or record cold everywhere. However, it increases the probability of extreme weather conditions: high pressure blocking the flow, cold air being "dug up" for many days, or severe cold spells coming earlier than the normal climate schedule.
Notably, this phenomenon occurs in the context of the Earth warming up. On average, winter in many areas becomes warmer, but extreme cold spells can still occur when the atmospheric system operates "slowly". This contrast makes winter increasingly unpredictable: Few cold lasts for a long time, but when cold, it can be very deep and very harsh.
For Vietnam, the North is forecast to welcome 2 consecutive cold air waves this week. The first batch is expected to arrive on December 17 and the second batch is expected to overflow on the night of December 20.
