Hurricane Simon, a Category 4 storm, moved dangerously close to Mexico's Pacific coast on October 11, 2026, with sustained winds of roughly 210 kilometers per hour. Although the storm's eye remained about 50 kilometers offshore, it brought torrential rain and flooding to coastal communities such as Manzanillo. The rugged Sierra Madre mountains appeared to weaken the storm, shrinking the area affected by its winds and reducing the threat to inland regions, though mudslides remained a concern.
While Simon churned across the ocean, NASA satellites detected something remarkable far above the clouds. Atmospheric gravity waves—disturbances that move through air rather than water—spread outward from the hurricane. These waves formed when powerful updrafts near the eyewall pushed warm, moist air upward into towering cumulonimbus clouds, sending ripples into the stratosphere and mesosphere.
The waves became visible because of airglow, a faint natural light produced by gases high in Earth's atmosphere. The VIIRS instrument's day-night band on the NOAA-21 satellite can detect subtle brightness variations caused by waves passing through this glowing layer. With very little moonlight reflecting off the surface, the delicate ripple patterns stood out clearly, allowing one of the rare satellite images of such atmospheric waves to be captured.
Forecasters later described confidence in Simon's track and intensity as "very low confidence," as the storm behaved unpredictably. Regardless of its exact path, large ocean swells were expected to create hazardous conditions along parts of Mexico's southwestern and west-central coastlines in the days that followed.