Rare Winter Echo Phenomenon Explained by Meteorologist Amid Weather Clash
The weather in Taiwan is undergoing a unique winter phenomenon, according to meteorologist Zheng Ming-tian. On January 19, the Central Weather Bureau (CWB) released radar composite echo images revealing an unusual amount of echo activity, something not typically seen during winter. This surge in echoes is largely attributed to the northward movement of southern cloud systems and increased moisture levels across the island.
Understanding the Rare Winter Echo Phenomenon
Zheng, a former CWB director, noted the radar echoes mainly concentrated over the ocean, indicating air currents are flowing around Taiwan’s terrain. This situation may suggest the presence of an inversion layer over the island. He explained that the radar composite echo map published today is associated with the “southern trough,” which encourages rainfall. In contrast, the inversion layer suppresses rain, creating a tug-of-war between these opposing forces that is critical to recent weather changes.
Details of the Southern Trough
The southern trough influencing Taiwan holds a remarkable structure. Analysis of the 500-hPa height field chart shows that the western side of Taiwan’s southern trough is not a single trough line but rather a series of short-wave troughs and ridges. This meteorological pattern is classified as a “positively unstable” reaction, with energy primarily sourced from jet stream kinetics. This phenomenon reflects the transformation of average meridional flows and ultra-long waves into short-wave kinetic energy.
Implications for Current Weather
- Increased chance of localized showers across the island today.
- Rain likelihood to rise throughout the day, peaking tomorrow morning.
- Expect cooler and humid conditions due to the northeast monsoon influence.
Moreover, the popular Facebook weather account, “Taiwan Typhoon Forum | Weather Urgent,” has warned that moisture from the south is moving upward, leading to a higher probability of rainfall as the day progresses. The first morning of January 20 appears to be the most likely time for rainfall. Residents are encouraged to stay alert to temperature fluctuations and to carry umbrellas for potential rain showers.
