Recently, meteorological phenomena such as "sudden stratospheric warming" (SSW) and "polar vortex collapse" have triggered discussions, and there are even rumors that the "overlord cold wave" of 2016 may reappear. In response, Jia Xingxing, director of the Taiwan Integrated Disaster Prevention Engineering Technology Consulting Company, posted on Facebook today (6th) to clarify that the sudden warming of the stratosphere and the entry of the Arctic Oscillation (AO) into a negative phase do not mean that Taiwan will definitely experience a dominant cold wave. The real key lies in the atmospheric circulation and the location of the cold air moving south. He also reminded that the northeast monsoon briefly weakened on Sunday (8th), and the daytime high temperature across Taiwan may approach 30 degrees. However, starting from next Monday (9th), the northeast monsoon will strengthen again, and the low temperature in the early morning in northern Taiwan may drop to 18 to 19 degrees. People should keep warm.
Jia Xingxing pointed out that sudden stratospheric warming refers to the abnormal warming of the stratosphere about 10 to 50 kilometers above the Arctic region in just a few days. It was first discovered by German meteorologist Richard Scherhag in 1952 through sounding observations. Such high-altitude atmospheric changes may affect the polar vortex and mid- and high-latitude circulation, but it usually takes about 2 to 4 weeks for the relevant signals to be transmitted downward to the surface, and not every occurrence will trigger a cold wave on the ground.
In response to the outside world's equation of sudden stratospheric warming with a dominant cold snap, Jia Xingxing took the January 2016 cold snap as an example. On January 24 of that year, Taipei measured a low temperature of 4 degrees Celsius, but the time when the negative phase of the Arctic Oscillation was strongest was not consistent with the actual low temperature; even during the negative phase of the Arctic Oscillation, Taipei experienced temperatures close to 18 degrees Celsius. He emphasized that one cannot conclude that Taiwan is about to experience extreme low temperatures based on a single atmospheric indicator.
Jia Xingxing explained that after the polar vortex is disturbed, the cold air may move southward along the westerly belt and the low-pressure trough blocking the high pressure periphery, but whether it affects Europe, North America or East Asia still depends on the atmospheric circulation configuration. If Taiwan is located near a relatively warm high-pressure ridge, it may not be affected by strong cold air; conversely, if it is located on the southward path of cold air, the cooling may be more obvious. Therefore, it is not appropriate to directly interpret changes in the polar vortex as an overbearing cold current in Taiwan.
As for the weather in the coming week, Jia Xingxing said that the northeast monsoon will temporarily weaken on Sunday (8th). The weather in Taiwan will be relatively clear and stable. The high temperature during the day may rise to close to 30 degrees, which is suitable for washing and drying clothes. However, this wave of warming will not last long. The northeast monsoon will strengthen again next Monday to Wednesday (9th to 11th), and northern Taiwan and Yilan will turn to wet and cool weather, with obvious cooling effects.
Jia Xingxing predicts that during this wave of northeast monsoon, the daytime high temperature in northern Taiwan may drop to 22 to 24 degrees, and the low temperature in the early morning and night is about 18 to 19 degrees, and it may be even lower in some open areas. The daytime temperature in the central, southern and eastern parts of the country may drop slightly by 1 to 2 degrees, with a large temperature difference between day and night. He reminded people going to work and school on Monday to wear long-sleeved clothing in a timely manner, and motorcycle commuters should especially prepare windproof jackets and rain gear to cope with rainfall on the windward side and falling temperatures.
As the northeast monsoon gradually weakens, Jia Xingxing predicts that daytime temperatures will gradually rise in various places starting from the 12th. The high temperature may reach 27 to 30 degrees, and the weather will become warm again. In addition, he also reminded the public to pay attention to the development of tropical systems. It is estimated that a typhoon may form from the 7th to the 8th, and mentioned the name "Chapaca". However, the actual formation, naming and subsequent path must still be subject to the latest information released by the Meteorological Administration.
Tomorrow (7th) coincides with the "Beginning of Winter" among the 24 solar terms. Jia Xingxing also reminded that people should pay attention to temperature changes during the seasonal change and should not overdose on dietary supplements. He stressed that what really needs attention in the near future is the rainfall and cooling brought about by the intensification of the northeast monsoon next Monday to Wednesday. As for whether the changes in the polar vortex will cause a strong cold wave in Taiwan, we still need to observe the subsequent development of atmospheric circulation, and there is no need to panic overly because of relevant rumors.
