南方入冬推迟：冬月飞蚊子 桂花又开了

Core Viewpoint - The winter season is significantly delayed in many southern regions of China, with temperatures remaining unusually high, attributed to weak cold air influences and a northward shift in cold air patterns [1][2][4]. Group 1: Weather Patterns - Southern cities like Shanghai, Chongqing, and Hangzhou have not yet officially entered winter, with temperatures exceeding 15°C, which is notably higher than the historical averages for this time of year [2][3]. - Shanghai's average winter onset date is December 5, but this year it is delayed by nearly 20 days, with the latest recorded winter onset being December 25, 2021 [2]. - Hangzhou has also broken its record for the latest winter onset, with temperatures reaching 21.3°C just before the winter solstice [2][3]. Group 2: Meteorological Analysis - The delay in winter is primarily due to the relatively straight mid-latitude westerlies since late November, which hinder the accumulation and southward movement of cold air [4]. - Cold air has been frequent but mainly affects regions north of the Yangtze River, with limited impact on southern areas, leading to a predominance of warmer temperatures [4]. - Data from Shanghai indicates that the prevailing winds have been from the northeast, southeast, and south, suggesting minimal influence from cold air [4]. Group 3: Upcoming Weather Changes - A significant cold front is expected to impact most of China from the night of December 23, leading to temperature drops of 4-6°C, with some areas experiencing drops of over 10°C [6]. - This cold air will likely facilitate the official onset of winter in southern cities like Shanghai and Hangzhou, which are projected to see temperature declines approaching 10°C [6].