AI Insight
Hurricane Simon, a Category 4 tropical cyclone, passed approximately 50 kilometers off Mexico's Pacific coast on October 11, 2026, with sustained winds reaching 250 kilometers per hour at peak intensity. Satellite imagery from VIIRS instruments captured both the hurricane's visible structure and atmospheric gravity waves extending into the mesosphere, visible through airglow emissions in nighttime observations. The storm's interaction with the Sierra Madre mountains reduced its wind field size and intensity somewhat, though it still delivered heavy rainfall and flooding to coastal areas including Manzanillo.
Why it matters
This event demonstrates the capability of modern satellite remote sensing to observe hurricane effects beyond the troposphere, including gravity waves propagating into the upper atmosphere. The observations highlight ongoing challenges in forecasting tropical cyclone behavior near complex coastal terrain and the persistent threat of major hurricanes to Mexico's Pacific coast population centers.
Understand the Science
Hurricane Simon, the latest in a long progression of tropical cyclones in the Eastern Pacific this season, passed close to the Mexican coast as a category 4 storm on October 11, 2026. Sustained winds reached 250 kilometers (155 miles) per hour as it crept north-northwest.
Simon’s eye was about 50 kilometers (30 miles) offshore, between Manzanillo and Puerto Vallarta, when the VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite acquired this image around 2:30 p.m. local time (20:30 Universal Time) on October 11.
By that time, sustained winds were about 210 kilometers (130 miles) per hour, according to the National Hurricane Center (NHC), and the storm’s inner core was brushing up against the coast. The topography of the Sierra Madre mountains appeared to temper the storm’s intensity somewhat and shrink the size of its wind field, the NHC noted. Still, the major hurricane delivered heavy rain and flooding to coastal areas, including the port city of Manzanillo, and raised the risk of mudslides in mountainous areas, according to news reports.
In the early morning hours of October 11, satellites captured the storm’s effects extending into the upper atmosphere. This nighttime image (above), acquired with VIIRS on the NOAA-21 satellite, shows atmospheric gravity waves radiating from the hurricane. These ripples form when latent heat released near the tropical cyclone’s eyewall drives strong convection, building tall cumulonimbus clouds with updrafts that can send waves into the stratosphere and mesosphere.
But these waves are not always observable. Winds in the upper atmosphere can dissipate them before they reach the mesosphere, where they show up as ripples in airglow—faint light emitted by gases at those high altitudes. The VIIRS day-night band is sensitive to airglow but also detects reflected moonlight, which can wash it out. On the night this image was acquired, minimal illumination from the Moon helped the airglow stand out.
On the morning of October 13, forecasts of Simon’s intensity and path remained “very low confidence,” as the storm’s evolution continued to defy meteorologists’ expectations. The system may steer north and enter the Gulf of California before making landfall. Large swells causing dangerous nearshore conditions were expected along portions of the southwestern and west-central coasts of Mexico in the coming days.
NASA Earth Observatory images by Michala Garrison, using VIIRS data from NASA EOSDIS LANCE, GIBS/Worldview, the Suomi National Polar-orbiting Partnership, and the Joint Polar Satellite System (JPSS). Story by Lindsey Doermann.
References & Resources
- Hoffmann, L., et al. (2018) Satellite observations of stratospheric gravity waves associated with the intensification of tropical cyclones. Geophysical Research Letters, 45, 1692–1700.
- NASA (2018, October 22) Why NASA Watches Airglow, the Colors of the (Upper Atmospheric) Wind. Accessed October 13, 2026.
- NASA Earth Observatory (2026, June 1) Gravity Waves From Super Typhoon Sinlaku. Accessed October 13, 2026.
- National Hurricane Center (2026, October 13) Hurricane SIMON Advisory Archive. Accessed October 13, 2026.
- Reuters (2026, October 12) Hurricane Simon crawls along Mexico’s Pacific coast, bringing floods and evacuations. Accessed October 13, 2026.
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