From August 22 through September 7, 2020, NASA’s IMERG algorithm estimated rainfall from three typhoons as they passed over the Pacific Ocean, Japan, and Korea. According to NOAA's records, this was the only time since records have been kept starting in 1945 that the Korean peninsula saw three landfalling typhoons in a single year, let alone in two weeks. Each of the three typhoons--Bavi, Maysak, and Haishen--reached the equivalent of “major hurricane” status, meaning Category 3 or above on the Saffir-Simpson hurricane-intensity scale (shown here as a red in the hurricane track) along their northward journeys toward the Korean Peninsula.

In this animation, the typhoons' low-pressure centers are tracked with lines whose color changes based on their intensity in NOAA storm-track data. Both Maysak and Haishen reached Category 4 status, with Haishen just shy of a Category 5 storm at its peak. Even though each storm weakened before making landfall, the cumulative effects of their winds and rainfall were reported to have led to evacuations and power outages that affected hundreds of thousands of people in southern Japan and Korea.

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This animation shows IMERG rain rates in blue and yellow shading overlaid with cloud data from infrared measurements on NOAA geostationary satellites, shown here in gray/white. Each of the three storms produced heavy rain rates throughout their paths, seen here in yellow shading (greater than 25 millimeters/hour, or 1 inch/hour). As the storms progressed, they left trails of heavy rainfall accumulation, shown in green shading; only values above 4 inches are shown here. The highest rainfall accumulations occurred over the Ryukyu Islands in southern Japan, with Okinawa estimated to have received over 60 centimeters (24 inches) of rain during this 17 day period (right edge of dark green shading).

A rain gauge station on Okinawa confirmed the >24-inch rainfall totals for the same time period, according to data from the NOAA National Climatic Data Center. Parts of Korea and Japan also saw high accumulations as a result of the three typhoons: Jeju Island, to the south of the Korean Peninsula, was estimated by IMERG to have accumulated between 25 and 40 centimeters (10 and 16 inches). The region around Busan, the second-largest city in South Korea and a major international shipping hub which was just kilometers away from both Maysak’s and Haishen’s landfalls, saw totals between 15 and 20 centimeters (6 and 8 inches).

Visualization and Story by Jason West (NASA GSFC)