Hosting not one, but two tropical cyclones at once is clearly bad news for any country. The Philippines, for example, has been severely affected by the twin tropical cyclones, Tropical Storm “Dante” and Typhoon “Emong,” on top of the southwest monsoon and the preceding Severe Tropical Storm “Crising.”
However, Dante and Emong are particularly of note due to their demonstration of a rare weather phenomenon known as the “Fujiwhara” effect. What exactly does this mean?
Independent weather and climate expert Royal Meteorological Society describes the effect as a “rare phenomenon that sees nearby cyclones ‘dancing’ round each other.”
“If the Tropical Cyclones are similar in size, they can move around one another for a few days, before taking their own paths. However, if the Tropical Cyclones are of different sizes, then the larger of the two will tend to dominate, with the smaller one orbiting around it,” the group explained.
“Sometimes, the smaller Tropical Cyclone will be consumed by the larger one and the two systems essentially merge, with the smaller storm dissipating and the larger storm remaining and moving away on its own,” it added.
As in Dante and Emong’s case, the Fujiwhara effect happens when two tropical cyclones are less than 1,500 kilometers apart, getting too close in proximity that they begin to “dance” or rotate cyclonically about each other.
In this case, Dante was the dominant of the twin cyclones. Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) weather specialist Benison Estareja on Wednesday said that Dante even kept Emong over the Ilocos Region temporarily.
The “dancing” of two cyclones makes it much more difficult for meteorologists to predict their trajectory and intensity. In turn, this leads to unexpected changes in forecasts with stronger rains and winds hitting areas that may not have been initially warned ahead of time.
Altogether, the combined strength of the two cyclones will have a significant impact on enhancing the southwest monsoon, according to the Philippine Information Agency (PIA).
As of Thursday afternoon, PAGASA announced that Dante has exited the Philippine Area of Responsibility (PAR).
Editor’s Note: This is an updated article. Originally posted with the headline: “What is Fujiwhara effect as seen in twin cyclones ‘Dante,’ ‘Emong’?”
