Core Viewpoint - The article discusses the impact of a cold wave affecting various regions in China, with temperatures dropping significantly, particularly in the northeast and northern areas, while also forecasting a subsequent temperature rebound. Summary by Sections - **Cold Wave Impact**: The article highlights that as of December 2, extreme cold weather has been recorded in northeastern regions, with temperatures dropping below -30℃ in parts of Inner Mongolia and Heilongjiang [1]. - **Temperature Forecast**: It is expected that on December 3, many northern areas will experience further drops, with temperatures reaching as low as -20℃ in several locations [1]. In contrast, southern regions will see a shift from previously high temperatures to much lower ones, with maximum temperatures around 10℃ [1]. - **Temperature Recovery**: Following the cold wave, temperatures are predicted to rebound significantly by the weekend, with increases of 6 to 10℃ in many areas, and up to 15℃ in northeastern regions, bringing temperatures above 0℃ [5]. - **Wind Alerts**: The Central Meteorological Observatory issued blue wind alerts, predicting winds of 5-6 levels in several northern regions and stronger winds of 7-8 levels in various sea areas, including the Taiwan Strait [7][8]. - **Cold Wave Warning**: A blue cold wave warning was issued, indicating a temperature drop of 6-8℃ in regions such as Huanghuai, Jianghuai, and parts of Jiangnan, with some areas experiencing drops exceeding 10℃ [10].

Group 1 - The recent heavy rainfall in northern China has been influenced by a combination of factors, including stable subtropical high pressure, prolonged convective activity, and orographic lifting from the Yanshan and Taihang mountains [2][4] - Specific areas such as Yixian in Hebei and Miyun in Beijing have experienced localized rainfall exceeding 400 to 500 millimeters, approaching their annual average precipitation [2] - The current heavy rainfall event is expected to gradually diminish by the 30th, as the subtropical high pressure retreats southward and moisture transport decreases [4] Group 2 - Typhoon "Zhu Jie Cao" is expected to impact the eastern China region, with forecasts indicating it may make landfall on the 30th, bringing significant rainfall to areas like southern Jiangsu, Shanghai, and eastern Zhejiang [5][7] - The typhoon's trajectory suggests it will slow down as it moves inland, necessitating close monitoring of its potential for sustained rainfall in the eastern regions [7] - The weather patterns indicate a shift from northern heavy rainfall to increased precipitation in the eastern coastal areas due to the typhoon's influence [5]

Core Points - The article discusses the recent severe weather events in Beijing, including thunderstorms, hail, and strong winds, and explains the meteorological conditions that lead to these phenomena [1][2][3] Weather Conditions - The cold vortex system is a significant factor affecting Beijing's weather during the spring and summer, leading to the formation of strong convective storms [1] - The transition period from spring to summer, particularly from May to June, is identified as a peak time for hail occurrences due to the warming ground and the influence of cold air aloft [1][2] - The combination of warm surface temperatures and cold air aloft creates unstable atmospheric conditions conducive to hail formation [2] Safety Measures - Recommendations for avoiding hazards during thunderstorms include staying away from high points, avoiding metal objects, and securing indoor environments [3] - In the event of hail, individuals are advised to seek shelter indoors or under sturdy cover, protecting themselves from potential injuries caused by falling hail [4] - During strong winds, outdoor activities should be halted, and precautions should be taken to secure loose items and avoid areas under tall structures or trees [6]

Group 1 - The article discusses the recent occurrence of severe convective weather in Beijing, including hail, thunderstorms, and strong winds, particularly during the transition from spring to summer [1][2] - Meteorological departments attribute these weather patterns to the influence of cold vortex systems, which, combined with moisture in the atmosphere, create unstable atmospheric conditions conducive to the formation of severe weather [1] - The period from May to June is identified as a peak time for hail formation due to warming ground temperatures and the continued influence of cold air aloft, creating favorable conditions for hail development [1] Group 2 - The article explains why hail often occurs at night, highlighting the role of daytime heating and the presence of cold air aloft that creates strong convective activity [2] - During the day, intense solar radiation heats the ground, causing air to rise and form strong updrafts, while at night, surface cooling leads to lower temperatures near the ground, but the cold air aloft remains, resulting in strong convection that can produce hail [2] - The interaction between warm, moist air near the surface and cold air above leads to repeated lifting and collision of water droplets and particles, ultimately resulting in hail formation [2]