https://phys.org/news/2018-12-nasa-india-landfall-tropical-depression.html > On Dec. 17 at 3:20 a.m. EST (0820 UTC) the MODIS instrument aboard NASA's Aqua satellite looked at Tropical Depression Phethai after it made landfall south of Visakhapatnam. Satellite imagery showed that the bulk of clouds and showers were north and east of the center of circulation indicating that wind shear was affecting the storm. > In general, wind shear is a measure of how the speed and direction of winds change with altitude. Wind shear can tear a tropical cyclone apart or weaken it.