Satellites See Fred Become Second Major Hurricane in Atlantic

Three NASA satellites had Fred in their sights when he became a major hurricane. QuikScat eyed his winds, Terra eyed his cloud cover, and Aqua eyed his cloud temperature, ice and precipitation.

At 11 a.m. EDT today, September 9, Hurricane Fred strengthened to a category three hurricane on the Saffir-Simpson Scale. That gives Fred the title of the “second major hurricane of the Atlantic Ocean season.”

Fred however poses no threat to land, as he’s far in the eastern Atlantic Ocean. In fact, Fred is 540 miles west of the southern-most Cape Verde Islands (off the coast of Africa). He’s near 13.9 north and 32.4 west. His maximum sustained winds are near 120 mph, but he’s moving northwest and into cooler waters, meaning he’ll start to weaken. His minimum central pressure is 958 millibars.

NASA’s Aqua satellite flew over Fred, and the Atmospheric Infrared Sounder (AIRS) instrument onboard captured infrared, visible and microwave imagery of the hurricane.

Infrared imagery measures temperatures and not only can it see cold, high cloud tops in tropical cyclones, but also the warm ocean waters that power the cyclones (if the sea surface temperatures are over 80F). Cold cloud top temperatures provide clues about the power of the thunderstorms in a tropical cyclone. The colder the clouds are, the higher they are, and the more powerful the thunderstorms are that make up the cyclone. Fred’s cloud temperatures were colder than minus 63 Fahrenheit, indicating very cold, high, strong thunderstorms within. The ocean waters beneath Fred are also over 80F, but as he tracks farther north, those temperatures will decline.

AIRS data is also coupled with data from the Advanced Microwave Sounding Unit (AMSU) that flies with AIRS on Aqua to create microwave images of storms. The AMSU image uses the radiances of the 89 GHz channel, and the cold areas in those images indicate where there is precipitation or ice in the cloud tops.

NASA’s Terra satellite also flew over Fred earlier today, September 9 at 8:55 a.m. EDT, and using the Moderate Imaging Spectroradiometer (MODIS) instrument captured an image of the storm that clearly shows Fred’s eye in the center of circulation.

Satellite Imagery Shows a Non-Symmetric Linda

Tropical Storm Linda doesn’t appear to be strengthening, and NASA infrared satellite imagery has shown that her shape isn’t symmetric confirming that. Satellite data also shows the bulk of her clouds and thunderstorms are northwest of her center.

Infrared imagery from the Atmospheric Infrared Sounder (AIRS) instrument on NASA’s Aqua satellite on September 9 around 6 a.m. EDT showed the bulk of Linda’s thunderstorms and high clouds lie to the northwest of Linda’s center of circulation. The other clouds and associated thunderstorms are scattered to her south and southeast.

At 11 a.m. EDT on September 9, Linda had maximum sustained winds near 65 mph. Based on satellite data and forecasts from the National Hurricane Center, she isn’t expected to strengthen in the next 24 hours. Linda is moving northwest near 8 mph and is expected to turn north-northwest in the next day or two. She poses no threat to land, however as her center is 1,300 miles west-southwest of the southern tip of Baja California, near 16.5 north and 128.7 west. Her estimated minimum central pressure is 994 millibars.

Forecasters at the National Hurricane Center noted that she still has the opportunity to strengthen a little in the next 24 hours, but thereafter she’ll be in cooler waters and the wind shear will increase, shooting down her chances of becoming a hurricane unless it happens before that time.