Satellites caught usually invisible waves rippling high above Category 4 Hurricane Simon

Satellites caught faint, concentric ripples spreading through the upper atmosphere above Category 4 Hurricane Simon on Oct. 11, 2026. A nighttime image from the VIIRS instrument aboard NOAA-21, captured in the early morning of Oct. 11, shows atmospheric gravity waves radiating from the storm as a semicircle of ripples in mesospheric airglow. Waves like these are usually invisible from space, which is what made the picture notable when NASA Earth Observatory published it on Oct. 14.

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Simon peaked with sustained winds of about 250 km/h (155 mph). At about 2:30 p.m. local time on Oct. 11, its eye sat roughly 50 km (30 miles) offshore, between the Mexican coastal cities of Manzanillo and Puerto Vallarta, with winds down to about 210 km/h (130 mph) according to the National Hurricane Center.

Latent heat at the eyewall becomes a wave in the airglow

The explanation comes from NASA Earth Observatory’s Hurricane Simon image story, written by Lindsey Doermann with imagery by Michala Garrison and republished by ScienceDaily. Latent heat released near the eyewall drives strong convection and towering cumulonimbus clouds. Updrafts inside those clouds push waves upward into the stratosphere and mesosphere, and in the mesosphere the waves modulate airglow, the faint light given off by gases at high altitude. The result is the rippling pattern that the day-night band of VIIRS recorded over the Pacific.

Airglow, as the Sinlaku write-up defines it, is light emitted when atoms and molecules excited by sunlight during the day release their excess energy later, which is why a sensor built for low light can see it after dark. Two satellites contributed. A daytime image from VIIRS on Suomi NPP, taken at about 2:30 p.m. local time (20:30 UTC) on Oct. 11, shows the hurricane’s cloud structure, while the nighttime NOAA-21 pass supplies the waves themselves.

Why upper-atmosphere winds usually erase the pattern

The Sierra Madre mountains, according to the National Hurricane Center, weakened the storm somewhat and shrank its wind field, but they did not stop the rain. The same write-up explains why such images are rare. Strong high-altitude winds can break up gravity waves before they become visible, and the day-night band can be washed out by reflected moonlight. On the night of Oct. 11, moonlight was minimal, which left the airglow ripples easier to pick out. Both conditions had to line up, the waves surviving the winds aloft and a dark sky behind them, for the pattern to show.

NASA’s earlier case offers a comparison. In a June 1, 2026 image story on Super Typhoon Sinlaku, Earth Observatory described concentric rings that resemble “ripples on a pond” in a VIIRS image from NOAA-20 taken April 12, 2026, with infrared data from the AIRS instrument on NASA’s Aqua satellite showing the same rings in the stratosphere. AIRS also showed the pattern on April 13 and 14. Sinlaku had strengthened from a Category 2 to a Category 5 storm in the 24 hours before the VIIRS image, and the page notes that light stratospheric winds and low moonlight helped the waves show.

Gravity waves as a possible intensification signal

Researchers have studied whether such waves carry information about a storm’s strength. A 2018 paper by Hoffmann, Wu and Alexander in Geophysical Research Letters is titled “Satellite Observations of Stratospheric Gravity Waves Associated With the Intensification of Tropical Cyclones,” and the NASA Sinlaku page says researchers believe such observations could help monitor storm intensification. The Simon write-up itself stops short of any claim about forecasting and gives no wavelength, period or speed for the waves.

That restraint matters for reading the image. What the pictures establish is that a Category 4 hurricane off Mexico’s Pacific coast produced waves reaching the mesosphere, and that a satellite sensor sensitive to faint light was positioned to see them on a dark night. Hurricane Polo had struck Mexico’s Baja California Peninsula as a Category 2 storm a week before Simon, so the same stretch of coast had little time between systems.

The sequence of the two satellite views is worth keeping straight. The waves were recorded in the early morning of Oct. 11, hours before the afternoon Suomi NPP image placed the eye roughly 50 km off the coast, so the ripples describe a storm that was still at or near its peak strength. The Sinlaku page adds that tropical cyclones can affect stratospheric weather and space weather, one reason researchers pay attention to what a hurricane does well above the clouds. NASA does not say whether Simon’s waves were measured against any intensity change, and no scientist is quoted in the write-up.

The storm on the ground, and an uncertain track

Below the ripples, the storm was causing real harm. Reporting from Oct. 11 described Mexican President Claudia Sheinbaum urging coastal residents in Jalisco, Colima, Nayarit and Michoacan to remain sheltered until authorities declared the danger had passed. Manzanillo resident Cecilia Palomar said of her flooded home: “The whole house was flooded.” At the 9 a.m. advisory on Oct. 11 the National Hurricane Center put Simon’s maximum sustained winds at about 230 km/h, moving north-northwest at about 11 km/h, and forecasters warned of damaging winds, dangerous storm surge and large waves even without a direct landfall. Precautionary evacuations were under way, emergency shelters opened, and the military and National Guard were deployed in Manzanillo, where residents of the Alameda neighborhood waded through shin-deep water while soldiers bailed out homes. Puerto Vallarta’s airport closed temporarily, and 28 municipalities in Jalisco and Colima were placed under the highest cyclone alert.

NASA’s page records the National Hurricane Center’s judgment as of Oct. 13 that forecasts of Simon’s intensity and path carried “very low confidence,” with one possibility being a northward turn into the Gulf of California before landfall. Heavy rain flooded coastal communities including Manzanillo and raised the risk of mudslides, and large ocean swells were expected to bring hazardous conditions to parts of Mexico’s southwestern and west-central coasts.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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