Suomi NPP Image Collage of Irma (IMAGE) NASA/Goddard Space Flight Center Caption NASA-NOAA's Suomi NPP satellite flew over Irma at 1:54 a.m. AST Sept. 5, 2017, when it was still a Category 4 hurricane., Night-time images showed a well-defined eye with convection most of the way around it. Both the infrared and Day-Night Band both show tropospheric gravity waves. Think of them the waves generated if you dropped a rock into a pond, but in this case it is convection punching upward. Credit NASA/NOAA/UWM/CIMSS/William Straka III Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.