Sunrise over the snow-capped peaks of the Himalayas Photo: IC

The China Meteorological Administration (CMA) on Monday debunked online claims that a tropical cyclone forming over the Bay of Bengal between October 26 and October 31 would “slam into the Himalayas” and bring exceptionally heavy snowfall to the southwestern part of China’s Xizang Autonomous Region, clarifying that the storm could affect southern Xizang but that the description of the online claims was inaccurate. 

According to Dong Lin, chief forecaster at China’s National Meteorological Center (NMC), a tropical depression is currently active over the Bay of Bengal and is expected to intensify into a cyclonic storm on Monday, with its strength comparable to the tropical storm category used in China. After forming, the storm is forecast to move westward initially and continue to intensify, potentially reaching the level of a very severe cyclonic storm, with sustained winds of 33 to 38 meters per second. The storm is expected to make landfall along India's eastern coast on October 28 as a severe or very severe cyclonic storm before turning northward and gradually weakening, chinanews.com.cn reported. 

Given the limitations of the forecast period, forecasts of the storm's post-landfall track and intensity remain uncertain. By the time it approaches the Himalayas, the system is expected to have weakened into a weak residual vortex, making online claims that the cyclone will “slam into” the Himalayas inaccurate, and its main body is impossible to cross the mountain range, Dong said. 

The NMC forecasts notable rain and snow across central and eastern Xizang on Friday and Saturday as a Bay of Bengal storm moves northward and interacts with a plateau trough. Shannan Prefecture, Xigaze and Lhasa in Xizang could see moderate to heavy snow or sleet, while parts of the southern border may experience heavy to exceptionally heavy snowfall, with 10 to 30 millimeters of precipitation and 5 to 25 centimeters of new snow accumulation. 

According to Chen Tao, chief forecaster from the NMC, the Qinghai-Xizang Plateau’s high terrain acts as a natural barrier, preventing the Bay of Bengal storm from crossing it. The heavy precipitation and snow forecast for southern Xizang is not directly attributable to the cyclone itself crossing the mountains, Chen told the Global Times on Monday. 

Chen explained that on Friday and Saturday, the circulation of the northward-moving Bay of Bengal storm is expected to drive southerly winds, continuously transporting warm, moist air toward the plateau. When this moisture encounters the southern slopes of the Himalayas, it will be forced upward. The orographic uplift along the southern slopes of the Himalayas will trigger heavy rain and snow. 

An eastward-moving westerly trough is expected to interact with the Bay of Bengal storm, boosting moisture transport and atmospheric uplift and intensifying precipitation. The storm’s circulation is forecast to weaken on November 1, bringing a significant reduction in rain and snow across southern Xizang, Chen said. 

According to Chen, the storm’s evolution will be influenced by the westerly trough, the subtropical high and South Asia’s terrain. If it weakens rapidly after landfall, reduced moisture transport could alter the intensity and distribution of precipitation in southern Xizang, requiring continuous monitoring and updated forecasts. 

According to Dong, whether heavy snowfall occurs in southwestern Xizang will depend not only on the cyclone’s track but also on the strength and position of the plateau trough, the residual vortex's intensity and moisture transport efficiency. As the forecast period is relatively long, the actual snowfall intensity and accumulation remain uncertain.