The Atmospheric Infrared Sounder or AIRS instrument aboard NASA's Aqua satellite captures infrared imagery. Infrared light provides information about the temperatures and heights of clouds, and reveals their locations.
On Dec. 15, 2012, AIRS imagery captured a powerful warm ring of thunderstorms surrounding the eye of Evan as it was located about 150 miles (235 km) east-southeast of Suva, Fiji. The eye was about 15 miles (25 km) in diameter at the time of the AIRS image. AIRS data show that cloud top temperatures surrounding the eye were as cold as -85 degrees Fahrenheit (-65 degrees Celsius), indicating very high thunderstorms that reached about 11 km (6.8 miles) into the troposphere.
AIRS also revealed fragmented convection along Evan's weakening southern side, over cooler waters. The coldest cloud-top temperatures shown in the AIRS imagery were in scattered cells in Evan's northern hemisphere, reaching -76 degrees Fahrenheit (-60 degrees Celsius).
At 11 a.m. EST (1600 UTC) on Dec. 15, Evan's maximum sustained wind speeds were near 75 mph (120 kph), making it a Category 1 hurricane on the Saffir-Simpson Scale. Evan was centered near latitude 19.0 south longitude 178.5 east, about 145 miles (230 km) east of Suva, Fiji. Evan has tracked south-southwestward for about the last 24 hours because it is still embedded within the southwesterly flow of the monsoon trough. Evan was moving south-southwestward at 12 mph (19 kph).
