12月中下旬气温有起伏，“时间表”提前看

Core Viewpoint - The claim that "a significant warming will occur before December 20" is not entirely accurate, as the temperature rise is mainly concentrated in specific regions, with a new cold front expected to impact the central and eastern parts of the country shortly [2][4]. Group 1: Temperature Changes - From December 17 to 18, most of the central and eastern regions of China experienced a temperature increase of 4 to 6 degrees Celsius, with some areas in Northeast China and eastern Inner Mongolia seeing increases of over 10 degrees Celsius [2][4]. - A new cold air mass is expected to arrive from Xinjiang on December 19, affecting most of the central and eastern regions, leading to a temperature drop of 4 to 6 degrees Celsius [2][4]. Group 2: Weather System Influences - The recent temperature fluctuations are attributed to frequent cold air activities, with a significant cold wave occurring from December 10 to 13, followed by a warming trend due to warm air advection and clear weather conditions [3]. - The direct cause of the cold air activities is linked to the eastward movement of a mid-latitude high-altitude trough and the southward splitting of the polar vortex, which enhances the cold air's influence [3]. Group 3: Future Weather Developments - The temperature in the central and eastern regions of China is expected to fluctuate significantly in mid to late December, with another cold air mass expected to bring temperature drops of 4 to 6 degrees Celsius from December 19 to 21, and localized drops exceeding 8 degrees Celsius [4]. - The forecast indicates that cold air will continue to affect China frequently over the next ten days, with notable cooling expected primarily in northern regions during the cold air processes around December 22 to 24 [4].