Did it land or was it near the sea? Why is it difficult to predict the movement of Typhoon "Sula"
According to the forecast from the Central Meteorological Observatory, Typhoon Sula, the 9th typhoon of this year, is gradually approaching the coastal areas from eastern Guangdong to southern Fujian. It may make landfall along the coast from Huilai, Guangdong to Hong Kong during the day on September 1st, or it may move in a southwest direction near the eastern coast of Guangdong. On August 30th, the Central Meteorological Administration issued an orange typhoon warning, and the China Meteorological Administration initiated a Level 2 emergency response for typhoons.
In the past two days, Typhoon "Sula" has formed a reverse "6" shape in the ocean east of Luzon Island in the Philippines. There is still disagreement on how to adjust the path of "Sula" in the future, whether it will make landfall or wipe over the sea.
Zhang Ling, the chief forecaster of the Central Weather Observatory, pointed out that the direction and speed of typhoon movement depend on the direction and size of the guiding airflow, and factors such as subtropical high pressure, southwest monsoon, and western trough are all factors that affect the guiding airflow of typhoons. If the guiding airflow is stable, the typhoon's movement will be more "honest". However, in reality, this is often not the case. Subtropical high pressure systems may experience various situations such as eastward retreat, westward extension, northward uplift, southward subsidence, as well as fractures and mergers. The intensity of the southwest monsoon is also constantly changing. The westerly trough can contract northward or carry cold air southward, which may lead to the direction and size of the typhoon's guiding airflow, thereby affecting the typhoon's movement.
Therefore, it is difficult to accurately predict typhoon paths. On the one hand, predicting typhoon paths requires considering multiple factors mentioned above, and the typhoon and its surrounding circulation patterns are dynamically developing. Various meteorological data during movement are constantly changing, which undoubtedly increases the difficulty of typhoon path prediction. On the other hand, the model results for predicting typhoon paths are calculated based on data data over a certain period of time. Complex circulation patterns, multiple weather systems, and other factors add many "variables" to the "equation" for calculating typhoon paths, leading to instability in the model prediction results. This is manifested by the possibility of significant inconsistency in the forecast results near the start of the reporting period.
Why is it more difficult to forecast Typhoon Sula, the 9th typhoon of this year, compared to previous years? Zhang Ling analyzed that firstly, the circulation situation around "Sula" is relatively complex, and with more airflow guiding the typhoon's movement, there are many possibilities for the direction of typhoon movement. At this time, there are multiple vortices around "Sula", and a change in the future subtropical high pressure situation will also affect its movement direction. At present, it is autumn and the activity of cold air is strengthening, so the westerly trough will also affect the movement of typhoon "Sula". Secondly, "Sura" is also affected by typhoons such as "Sea Anemone" and tropical depressions on the east side of Guam. Two adjacent vortices at an appropriate distance may have a direct impact on each other's paths, known as the "Fujiwara effect", which refers to two typhoons rotating counterclockwise around the midpoint of their connecting line, directly affecting their movements; The existence and development of Typhoon "Sea Anemone" and the tropical depression on the east side of Guam will affect the surrounding environment of Typhoon "Sura", thereby affecting its path direction; The prediction of typhoon paths requires the use of numerical models and forecasting algorithms. However, small typhoons also have small scales, and the number of numerical grids covering small typhoons and the spatial resolution of numerical models make it difficult to form a precise internal structure characterization, thus increasing the difficulty of typhoon path prediction.
According to the Central Meteorological Observatory, the intensity of Typhoon "Sula" is expected to continue for the next 12 hours and gradually weaken thereafter. It is expected that the intensity will remain strong at the time of landfall, reaching the level of a strong or super typhoon. In addition, the water vapor transport brought by the southwest monsoon in Sula will bring strong wind and rain effects to the passing areas, with gusts of up to level 17 or higher in the nearby areas. Therefore, coastal areas need to focus on defending against the adverse effects of strong wind weather.
Experts suggest that regardless of whether Typhoon "Sula" makes landfall or grasps near the sea, considering its high intensity, the impact of wind and rain will inevitably be more severe. Therefore, the string of risk prevention and disaster reduction still needs to be constantly tightened.
