https://phys.org/news/2018-10-nasa-imerg-reveals-hurricane-willa.html

At NASA's Goddard Space Flight Center in Greenbelt, Maryland a rainfall accumulation analysis was generated by totaling Integrated Multi-satellitE Retrievals for GPM (IMERG) data for the period from October 20 to 26, 2018. The IMERG rainfall accumulation data indicated that Willa produced rainfall totals greater than 20 inches (508 mm) in the Pacific Ocean off Mexico's coast. IMERG data also indicated that rainfall accumulations of over 15 inches (381 mm) occurred in parts of Mexico and Southeastern Texas.

IMERG data are generated every half hour by NASA's Precipitation Processing System by merging data from the satellites in the GPM Constellation, and calibrating those data with measurements from the GPM Core Observatory as well as rain gauge networks around the world. IMERG data are provided for much of the globe. Full coverage is calculated over latitudes from 60 degrees north to 60 degrees south with the remaining areas of the globe being partially covered.