January 2015, two tropical cyclones— Diamondra and Eunice—swirled over the central Indian Ocean. Neither storm was particularly strong, nor were they expected to make landfall or cause significant damage. But their close proximity offered striking views to satellites.
The two storms were about 1,500 kilometers (930 miles) apart on January 28, 2015, when VIIRS imaged them. Eunice, the stronger of the two, was located to the west of Diamondra. Eunice had maximum sustained winds of about 160 kilometers (100 miles) per hour, while Diamondra’s maximum winds topped out at about 100 kilometers (60 miles). Both storms were moving in a southeasterly direction.
On January 28, 2015, geostationary satellites maintained by EUMETSAT and the Japanese Meteorological Agency collected the infrared data used to make the composite image at the top of the page. The Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP captured the lower image, another composite.
If two tropical cyclones draw near each other, they begin to rotate cyclonically around an axis connecting their centers—something meteorologists call the Fujiwhara Effect. Such binary storms can even merge if their centers get close enough.