1. If two cyclones move into each other’s domain, things become interesting. The natural, almost magnetic attraction results in an interaction known as the Fujiwhara effect.
2. In this situation, the two cyclones begin to orbit around a common centre, almost like a dance. Cyclones spin clockwise in the southern hemisphere, and the two cyclones will also rotate around each other in a clockwise fashion.
3. It’s usually not an equal playing field, with a bigger cyclone appearing to push the smaller one around. If they come close enough, they can change direction significantly from their previous paths – by as much as 90 degrees – as they wander towards each other.
4. Eventually they can merge and form a bigger cyclone if they move close enough, within 300 km of each other. Or, if each cyclone moves too far away from each other’s influence, they can drift apart and regain their independence.
The effect is named after Sakuhei Fujiwhara, the Japanese meteorologist who initially described it in a 1921 paper about the motion of vortices in water.
If two cyclones pass within 900 miles of each other, they can start to orbit, what happens next depends on the size of each storm.
5. If one storm is much stronger than the other, the smaller storm usually rotates around the larger one.
6. But when both storms are similar in strength, they tend to orbit a common center between the two.
The Fujiwhara effect isn’t limited to cyclones. In fact, Fujiwhara’s original studies also looked at spinning water in tanks and canals.
In the tropical atmosphere the Fujiwhara effect influences cyclones. But it also affects how storms behave in the frigid polar regions. It can even affect eddies in your local creek or bathtub.
The Fujiwhara effect can make forecasting cyclone track and intensity more challenging.
It adds to the number of scenarios can occur as the systems move and develop. The
'tug of war' these cyclones play out is makes difficult for the meteorologists to factor into
the cyclone forecasts.
Tropical cyclones and Fujiwahra, may directly and indirectly affect health in many ways, for example by:
– increasing cases of drowning and other physical trauma;
-increasing risks of water- and vector-borne infectious diseases;
-increasing mental health effects associated with emergency situations;
-disrupting health systems, facilities and services, leaving communities without
access to health care when they are needed most;
-damaging basic infrastructure, such as food and water supplies and safe
When tropical Fujiwahra cyclones cause floods and sea surges, the risk of drowning
and water- or vector-borne diseases increase. Additionally, flood waters may contain
sewage and chemicals, hide sharp objects made of metal or glass and electrical
lines, or host dangerous snakes or reptiles, which can cause diseases, injuries,
electrocution and bites.