Science & Technology

Severe Tropical Cyclone Yasa Bearing Down on Island Nation of Fiji

December 16, 2020

The South Pacific island nation of Fiji is bracing for the arrival of severe tropical cyclone Yasa. Citizens were told to evacuate low-lying areas in anticipation of a storm that will likely have category 4 or 5 strength when it arrives on December 17, 2020. Tropical cyclone warnings and flash flood alerts were issued for Vanua Levu, Viti Levu, the Yasawa and Mamanuca groups, and smaller surrounding islands.

As of midnight Fiji standard time on December 17, the reported sustained winds of 140 knots (260 kilometers/160 miles per hour). The center of the category 5 storm was about 400 kilometers (240 miles) northwest of Suva, Fiji. The storm’s eye appeared to be headed between the islands of Viti Levu and Vanua Levu. Forecasters noted that wave heights around the eye of the storm could approach 14 meters (45 feet).

The natural-color image above was acquired in the early afternoon on December 16, 2020, by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite.

Yasa emerged as a tropical storm on December 12 and organized into a cyclone by December 14. Over the next 36 hours, wind speeds increased by 130 kilometers (80 miles) per hour—well beyond the threshold increase of 55 kilometers (35 miles) per hour that meteorologists refer to as “rapid intensification.”

December 15, 2020 JPEG

Yasa has had plenty of fuel for growth, as the storm developed and evolved over warm South Pacific waters known to fuel cyclonic storms. The map above shows sea surface temperatures (SSTs) in the region as measured on December 15, 2020. Scientists have established that ocean temperatures should be at or above 27° Celsius (80° Fahrenheit)—red on the map—to sustain a cyclone or hurricane. The SST data come from the Multiscale Ultrahigh Resolution Sea Surface Temperature (MUR SST) project. MUR SST blends measurements of sea surface temperatures from multiple NASA, NOAA, and international satellites, as well as ship and buoy observations.

Yasa is the fifth storm worldwide to reach category 5 strength in 2020 and the second to do so in the South Pacific. (Tropical Cyclone Harold hit Vanuatu in April.) Only one previous category 5 storm on record has made landfall in Fiji: Tropical Cyclone Winston in 2016.

NASA Earth Observatory images by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview and sea surface temperature data from the Multiscale Ultrahigh Resolution (MUR) project.

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