Will Two Typhoons Collide? What Is the Fujiwhara Effect?
TyphoonSays·防御问答 · Typhoon knowledge · 更新 at 2026-10-10
Will Two Typhoons "Collide Head-On"? Unveiling the Fujiwhara Effect
During the summer and autumn seasons in the Northwest Pacific, it is common to see multiple typhoons active simultaneously. Many people worry that they might physically collide like vehicles. However, as massive low-pressure cyclonic systems with diameters spanning hundreds of kilometers, typhoons rarely make direct "hard contact." When two typhoons approach within a certain distance (typically within 1,000–1,500 km), their pressure fields and airflows exert significant mutual attraction, causing their paths to deflect, rotate, or even merge. This interaction is known in meteorology as the "Fujiwhara Effect," proposed by Japanese meteorologist Sakuhei Fujiwhara in 1921. Figuratively speaking, this is not a bumper-car collision but rather a complex "pas de deux," where the systems constrain and influence each other, potentially leading to separation, merger, or the dissipation of one.
Three Typical "Dance Steps" of the Fujiwhara Effect
The specific manifestation of the Fujiwhara Effect depends on the intensity contrast between the two typhoons and the surrounding atmospheric environment, primarily presenting in three modes:
- Mutual Rotation: If the two typhoons are of similar strength, they will rotate counterclockwise around a central point between them. During this phase, their paths become highly unstable, significantly increasing forecasting difficulty and raising the likelihood of sudden turns or stagnation.
- Engulfment and Absorption: If there is a significant disparity in strength, the stronger typhoon usually dominates. The weaker typhoon may rotate around the stronger one and eventually be absorbed into its circulation. In such cases, the strong typhoon may intensify further due to energy supplementation, escalating its destructive potential.
- Repulsion and Separation: Under the guidance of specific background wind fields, two typhoons may also repel each other, moving in different directions with little to no mutual interference.
Since forecasting must account for both environmental airflow and the interference from the other typhoon, track forecast errors during dual-typhoon events are typically greater than during single-typhoon events. The public should be mentally prepared for this uncertainty.
Key Defense Priorities in Complex Situations
When two typhoons coexist, weather conditions often become more unpredictable and volatile. The outer cloud bands of the two systems may overlap, leading to wider rainfall coverage, longer duration, and even a resurgence of intensity after a temporary lull in wind and rain. Therefore, the core of defense lies in "guarding against changes" and "avoiding risks":
- Beware of Recurring Wind and Rain: Do not venture out or lower your guard just because the wind and rain temporarily subside. Stay attentive to meteorological developments throughout the event.
- Strictly Follow Warnings: Pay close attention to official typhoon warning signals. According to national standards, typhoons are classified into five levels, from Tropical Storm to Super Typhoon. When a Yellow warning or higher is issued, outdoor activities should be reduced; if an Orange or Red warning is issued, measures such as school and work suspensions may be implemented in certain areas. Please refer to local government announcements for specific implementation standards and emergency response levels.
- Prepare Supplies: Check the security of windows and doors, clear balconies of items that could fall, and stock up on at least three days' worth of drinking water, food, and emergency medications to ensure basic living needs can be met during extreme weather.
In the face of changing meteorological conditions, staying informed is key to safety. Real-time typhoon tracks can be queried at TyphoonSays (taifengshuo.com)
This article is original educational content from TyphoonSays. Please refer to the latest official announcements from local governments for policy standards.