NASA captures Isaias bringing heavy rains to the Northern Bahamas

After forming into a tropical storm in the eastern Caribbean, Isaias crossed over Hispaniola and back into the western Atlantic heading northwest towards the Bahamas. During this time, Isaias strengthened into a Category 1 hurricane before then passing through the southern and central Bahamas. As it crossed Andros Island in the central Bahamas, Isaias also came under the effects of southwesterly wind shear, which together with the land interaction caused it to weaken back to a strong tropical storm. This animation follows Isaias into the central Bahamas using NASA’s IMERG rainfall product. With IMERG, precipitation estimates from the GPM core satellite are used to calibrate precipitation estimates from microwave and IR sensors on other satellites to produce half-hourly precipitation maps at 0.1 degree horizontal resolution. After it crossed Andros Island, Isaias was overflown by the GPM core satellite itself at 09:11 UTC (5:11 am EDT) on the morning of Sunday August 2^nd, which is detailed in the second part of the animation. Here rainfall rates derived directly from the GPM Microwave Instrument (or GMI) and Dual-Polarization Radar (or DPR) provide a detailed look into Isaias. GPM shows a large area of heavy rain (shown in red) covering the northern Bahamas. GPM also shows that this rain is located almost entirely northeast of Isaias’ center with very little rain on the western side of the storm. This highly asymmetric structure reflects both the effects of the wind shear as well as Isaias’ lack of intensity and hence ability to wrap precipitation around to the western side of the circulation. At the time of the GPM overpass, Isaias’ maximum sustained winds were reported at 65 mph by the National Hurricane Center, making it a strong tropical storm. Isaias would go onto regain hurricane intensity due to the warm waters of the Gulf Stream before making landfall on the southern coast of North Carolina.

GPM data is archived at https://pps.gsfc.nasa.gov/