Favorable environmental conditions and warm waters in the Gulf allowed tropical storm Harvey to restructure and strengthen over several days.
On August 25, Harvey became a category 4 hurricane.
The Global Precipitation Measurement (GPM) Core Observatory saw several passes.
GPM captured the hurricane continuously over land and ocean, observing the storm beyond the reach of land-based radars.
As Harvey slowly moved southeast, GPM showed an asymmetric rainfall pattern
with a massive swath of rain reaching north and east of the hurricane’s center.
NASA's Integrated Multi-satellite Retrievals for GPM estimated over 30 inches of rain from August 21 to 29.
The rainfall has lead to catastrophic flooding and difficult relief efforts.