Will two storms destroy each other or will they merge and become a more powerful monster?
Before a storm makes landfall, it is difficult to quantify its destructive power on both human life and property. So what happens when two storms collide?
There have been numerous science fiction movies based on the phenomenon of two hurricanes merging. However, in reality, this phenomenon is much more complex than what is depicted in films.
Fujiwhara Effect (or double storm effect) is named after Dr. Sakarei Fujiwhara, a Japanese meteorologist who first observed the interference of two storms and described this phenomenon in 1921.
According to Fujiwhara, two or more tropical low-pressure systems will only “interact” if they are within 1,900 km (about 1,180 miles) of each other.
The phenomenon of interference between two or more storms occurs when they form close to each other.
Meanwhile, two storms will “interact” whenever the distance between them falls below 1,400 km (about 870 miles), and they can potentially merge into one if they are within 300 km (about 186 miles) of each other.
The phenomenon of interference between two or more storms occurs when they form close to each other or intersect on their path.
So what happens when storms collide? Do they merge into a superstorm? Or does the larger storm extinguish the smaller one?
Principle of the Double Storm Effect: Interaction Leading to Path Changes
According to the theory of the Fujiwhara Effect:
- If one storm is weaker than the other, the smaller storm usually orbits around the larger storm.
- If both storms are of comparable strength, they will rotate together around a common point.
- If two equally strong storms come within 300 km of each other, they have the potential to merge into a superstorm.
For example, during the Atlantic hurricane season in 1995, Hurricane Iris “interacted” with Hurricane Humberto, then went on to “merge” with Tropical Storm Karen.
In the fall of 2005, Hurricane Wilma “absorbed” Tropical Storm Alpha shortly after sweeping through South Florida (USA).
One of the most famous examples of the Fujiwhara phenomenon is the “Perfect Storm” of 1991, which formed due to a cold air mass leaving the East Coast of the United States, along with a low-pressure area east of Nova Scotia and a storm named Grace.
However, there are also unique cases where two storms move close enough that the weaker storm gets “thrown off,” forced to change direction. An example is the interaction between Hurricanes Hilary and Irwin in July 2017.
Natural Disasters Can Occur Due to the Double Storm Effect
With the rise of global climate change, storms are increasingly attacking coastal areas, making the double storm effect more likely to occur.
Heavy rainfall is one of the most common disasters associated with the double storm effect. The rainfall caused by two storms in the affected area is greater than that of a single storm under normal conditions, and the duration of the rain is prolonged, making heavy rain one of the most severe disasters in coastal regions.
Heavy rainfall puts immense pressure on local irrigation systems, and urban drainage systems can become overwhelmed, leading to severe flooding. Additionally, heavy rain can cause secondary disasters such as flash floods and landslides, significantly affecting transportation, agricultural land, and the lives of local residents.
The double storm effect also causes strong winds, another major cause of severe damage. Two storms within the double storm effect will accelerate wind speeds, potentially destroying houses, damaging power facilities, and paralyzing transportation systems. Strong winds can also cause weather phenomena such as heavy rain, thunderstorms, and hail, exacerbating the severity of the disaster. To mitigate damage caused by strong winds, it is crucial to implement appropriate risk prevention measures in advance, including reinforcing homes and repairing electrical infrastructure to protect the lives and properties of local residents.
Coastal waves are also affected by the double storm effect. Sea levels in areas impacted by two storms simultaneously are higher, potentially forming large waves that cause severe coastal erosion and flooding in coastal regions. Erosion from waves not only directly removes sand from coastal areas but can also damage buildings and infrastructure near the shore. At the same time, waves can raise tidal levels, causing flooding that poses a severe threat to residents and agricultural land in coastal areas.
