The Global Precipitation Measurement mission or GPM core satellite, a joint mission between NASA and the Japan Aerospace Exploration Agency can measure rainfall from space.
That rainfall data, combined with data from other satellites provided a tally of Hurricane Maria’s rainfall over the course of several days.
At NASA’s Goddard Space Flight Center in Greenbelt, Maryland, NASA’s Integrated Multi-satellitE Retrievals for GPM (IMERG) data were used to estimate the total amount of rain that Hurricane Maria dropped from Sept. 17 to early Sept. 21, 2017. During that period Maria dropped heavy rain in the Leeward Islands, Virgin Islands and Puerto Rico. IMERG estimated that rainfall totals greater than 10 inches (254 mm) were common along Maria’s track. IMERG rainfall estimates indicated that more than 20 inches (512 mm) of rain fell over a large part of Puerto Rico.
Extreme flooding was reported in the streets of San Juan, the capital of Puerto Rico. The National Weather Service issued flash flood warnings for the entire island. Hurricane Maria has now moved to the northwest of Puerto Rico but is still expected to contribute to rainfall over the island on Friday. Feeder bands of thunderstorms are transporting rain over Puerto Rico and the Dominican Republic even as the hurricane moves toward the Turks and Caicos Islands.
