Several cold fronts have affected the United States and Canada this winter, and a cold front is expected to intensify in early to mid-January.
Although the timing and intensity of the new cold front are unknown, there are signs that the atmosphere is changing, and cold weather will spread across the United States and southern Canada.
Weather is a global phenomenon, and events in other parts of the world could affect North American weather. One of the influencing factors is the La Nina phenomenon, which is developing in the Pacific Ocean.
Although La Nina has been forecast for many months, it has not yet fully developed. Although the sea surface temperatures near equatorial in the east of the track change to lower than normal, they are not low enough to be considered a complete La Nina state.
However, the temperature has dropped rapidly in the past few weeks. Sea waves bring cool water up from below, along with strong trade winds pushing warm water westward, causing sea surface temperatures to drop below La Nina thresholds on December 16, according to a report from the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center.
At the same time, a series of thunderstorms moving along the equator will change weather patterns. These thunderstorms, called the Madden-Julien Oscillation (MJO), will change direction and fuel the atmosphere, changing air flows. The MJO will move across the Americas, Africa and return to the Indian Ocean in early January.
When the MJO is active in the winter in the Northern Hemisphere, it typically creates an atmospheric trough around Alaska and northwestern Canada, carrying cold air from the Arctic. The strength and location of this trough will determine the upcoming cold spell.
Another important factor is the appearance of a high-pressure dome moving into the Himalaya and Tibet, called an East-Asian Mountain Torque event, which will strengthen the cold trough in western North America and Alaska, supporting MJO in creating this cold spell.
A typhoon could bring stronger cold air, and models suggest the cold will sweep in on New Year's Eve or early in the new year.
It is especially noteworthy that this cold spell is not related to the interruption of the poles, a phenomenon that often causes prolonged cold weather in many areas such as Asia, Europe or North America. If this cold spell is not affected by the extreme cyclone, the weather could be colder and the cold spell in January could be worse.
The La Nina phenomenon has a clear impact on the weather in the world, including Vietnam. La Nina causes cold air from Siberia and continental Asia to strengthen to the south. As a result, cold air waves flooded into Vietnam more strongly and more frequently, causing temperatures to drop significantly, especially in the Northern region.
During La Nina years, winter in Vietnam often lasts longer with more severe cold spells.
