Severe storms struck the South Central U.S. on May 17, 2021, producing heavy rain, extensive flooding, damaging winds, large hail, and several tornadoes. Louisiana and Texas were hit particularly hard. NOAA satellites monitored the atmospheric conditions that spawned the storms and helped the National Weather Service forecast the severe weather potential in advance. They also tracked the storms in near-real time, providing vital information to forecasters.
Hail the size of baseballs was reported near Girard, Texas, and wind gusts of more than 70 mph downed trees and damaged buildings. The storms produced several tornadoes in Louisiana and Texas.
Torrential rain fell over parts of eastern Texas and Louisiana, producing widespread flooding. This flooding, which was particularly extreme in southwestern Louisiana, prompted the state’s governor, John Bel Edwards, to declare a state of emergency. At least four people died amid floodwaters after more than a foot of rain fell in Lake Charles and 10 inches in Baton Rouge.
GOES-16 monitored several supercells—storms with rotating updrafts—that spawned tornadoes. A variety of GOES-16 imagery highlights the severity of the storms. Visible satellite imagery captured detailed information about cloud properties, including the presence of overshooting tops and gravity waves, which indicate a storm may be severe.
Infrared imagery provides information on the temperature of the cloud tops. The colder the cloud top, the more likely the storm is producing heavy rain and severe weather. Combining visible and infrared data into one image is called “sandwich” imagery. The mix of visible data and temperature from infrared imagery helps identify key formations in a storm. Dark red areas are colder cloud tops, which indicate areas of greater storm intensity.
GOES-16 also revealed significant lightning activity within the storms. Rapid increases in lightning activity often precede severe and tornadic thunderstorms and monitoring lightning activity helps forecasters identify storms that are likely to become dangerous.
Meanwhile, the ATMS instrument on the NOAA-20 and Suomi-NPP satellites measured the temperature and water vapor of the storm, helping forecasters make predictions on the storm’s direction and intensity.
GOES-16 (GOES East) orbits 22,236 miles above the equator, at the same speed Earth rotates. This means the satellite has a constant view of the same area and can capture storms in motion. The ability to monitor clouds and atmospheric conditions in near-real time helps forecasters track rapidly changing weather conditions and give advance warning of severe thunderstorms, tornadoes, and flooding.
The NOAA-20 and Suomi-NPP satellites orbit the Earth from pole to pole at an altitude of 512 miles, providing high-resolution imagery and taking temperature and moisture measurements throughout the atmosphere.