The Global Precipitation Measurement or GPM core satellite flew over Grace in the Eastern Atlantic Ocean as it weakened to a depression. GPM found that the weaker storm only contained light rain.
On Saturday September 5, 2015 a tropical disturbance south of the Cape Verde Islands in the eastern Atlantic Ocean was designated tropical depression number seven (TD7). TD7 was subsequently upgraded to tropical storm Grace that evening after the tropical depression showed increasingly better organization. Now, just three days after it formed, it has weakened back to a depression.
Grace is moving into an area of the Atlantic Ocean where adverse vertical wind shear and dry mid-level air is predicted to cause the tropical storm to dissipate to a trough of low pressure within a few days. The GPM core observatory satellite passed above Grace on September 8, 2015 at 1226 UTC (8:26 a.m. EDT). At NASA's Goddard Space Flight Center in Greenbelt, Maryland, GPM's Microwave Imager (GMI) data was overlaid on a NOAA GOES-East Visible/Infrared image showed Grace contained only scattered areas of light rain.
GPM is a satellite that is co-managed by NASA and the Japan Aerospace Exploration Agency.
National Hurricane Center forecaster Richard Pasch noted in the discussion on Tuesday, September 8, "After the overnight burst of deep convection, thunderstorm activity has diminished and the overall cloud pattern remains disorganized."
At 11 a.m. EDT (1500 UTC) on September 8, the center of Tropical Depression Grace was located near latitude 14.3 North, longitude 42.8 West. That's about 1,235 miles (1,990 km) east of the Lesser Antilles. Satellite data indicate that the maximum sustained winds have decreased to near 35 mph (55 kph) with higher gusts. The estimated minimum central pressure is 1007 millibars.
The depression is moving toward the west near 20 mph (31 kph) and it is expected to continue in that direction over the next two days.
The NHC forecast expects Grace to move through an environment of increasing vertical shear and dry mid-level air for the next few days. Those are two factors that should cause the system to weaken further, and to degenerate into a remnant low pressure area over the next day or two.