September 6, 2017

Hurricane Irma seen by Suomi NPP satellite

Hurricane Irma seen by Suomi NPP satellite

On September 6, 2017, Hurricane Irma—an unusually powerful category 5 storm—slammed into the Leeward Islands on its way toward Puerto Rico and possibly the U.S. mainland.

By definition, category 5 storms deliver maximum sustained winds of at least 157 miles (252 kilometers) per hour. When it hit the Leeward Islands, Irma’s winds surpassed 185 miles (295 kilometers) per hour—making it the strongest storm to ever hit the islands and the strongest storm 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 6 as the eye was over the island of Barbuda. 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.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired the second image at 10:35 a.m. local time (14:35 Universal Time) on September 6, 2017. By then, the storm had also hit Anguilla and was poised to strike the Virgin Islands. While damages on Barbuda and Anguilla may not be as severe as feared, the islands of St. Barthelemy and St. Martin experienced extensive damage, according to news reports.

Irma’s winds are not only strong; they spread across a remarkably wide area. Hurricane force winds extend 50 miles (85 km) from the center; tropical-storm-force winds extend up to 185 miles (295 km).

Meteorologists recorded the lowest central pressure (914 millibars) ever for a storm outside of the Gulf of Mexico and western Caribbean. On September 6, Irma had already generated more accumulated cyclone energy—a term meteorologists use to describe the destructive potential of a hurricane based on the strength of its winds and their duration—than the first eight named storms of the Atlantic hurricane season combined, according to Philip Klotzbach of Colorado State University. Irma even broke a record for generating the most accumulated cyclone energy in a 24-hour period.

The latest National Hurricane Center forecast calls for the hurricane to turn west-northwest after grazing Puerto Rico, the Dominican Republic, and Haiti. After that, the potential track area shows Irma’s path will likely move over or near the Turks and Caicos Islands, the Bahamas, and may eventually make landfall on Florida.

Image Credit: NASA Earth Observatory
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