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Hurricane Irma Strengthens

Hurricane Irma Strengthens

On September 5, 2017, Hurricane Irma intensified into a strong and “potentially catastrophic” category 5 storm. By definition, category 5 storms deliver maximum sustained winds of at least 157 miles (252 kilometers) per hour. Irma’s winds that morning approached 180 miles per hour—the strongest ever measured for an Atlantic hurricane outside of the Gulf of Mexico or north of the Caribbean.

The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this nighttime view of the storm in the early hours of September 5. The image was acquired by the VIIRS “day-night band,” which detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe signals such as city lights, auroras, wildfires, and reflected moonlight. In this case, the clouds were lit by the nearly full Moon. The image is a composite, showing storm imagery combined with VIIRS imagery of city lights.

When the image was acquired, the storm’s center was moving due west. A National Hurricane Center forecast called for the hurricane to turn west-northwest toward the northern Leeward Islands. After that, the potential track area shows Irma’s path could move over areas between Puerto Rico, Cuba, and Florida.

NASA Earth Observatory image by Joshua Stevens and Jesse Allen, using VIIRS day-night band data from the Suomi National Polar-orbiting Partnership. Caption by Kathryn Hansen.

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