Tropical Cyclones can generate a tremendous amount of rainfall, and NASA's IMERG program utilizes a variety of data to create rainfall maps. Those maps provide estimates of where the heaviest rainfall occurred and NASA recently added up the rainfall dropped from Typhoon Prapiroon in the Northwestern Pacific Ocean.
Typhoon Prapiroon developed in the northwest Pacific Ocean east-northeast of the Philippines on June 28, 2018. Prapiroon became a typhoon on July 2 as it approached the Korea Strain between Japan and Korea. Stormy weather had already produced heavy rainfall in Korea and Japan before Typhoon Prapiroon moved through the area.
Estimates of Prapiroon's accumulated rainfall were made using IMERG (Integrated Multi-satellitE Retrievals for GPM) data at NASA's Goddard Space Flight Center in Greenbelt, Maryland. The rainfall data covered the period from June 28 to July 6, 2018. GPM or the Global Precipitation Measurement mission is a joint mission between NASA and the Japan Aerospace Exploration Agency, JAXA.
IMERG estimates indicated that Prapiroon combined with the other stormy weather dumped over 512 mm (20.2 inches) in some areas. IMERG estimated that the heaviest rainfall over land during this period fell from South Korea through southwestern Japan. Prapiroon caused mudslides, flooding and at least one death in South Korea.
For the history on Prapiroon, visit NASA's Hurricane Page: https://www.nasa.gov/feature/goddard/2018/09w-northwestern-pacific-ocean