Featured Images

Text Size

Hurricane Season 2008: Ivan (Indian Ocean)
02.11.08
 

Feb. 21, 2008

Active Cyclones in the South Indian Ocean

TRMM image of Tropical Cyclone Nicholas Credit: Hal Pierce, NASA GSFC/SSAI
> Larger image With tropical cyclone season near its peak in the South Indian Ocean, two cyclones were recently active in the region: Nicholas a one-time Category 1 cyclone that made landfall in far Western Australia and Ivan a powerful Category 4 cyclone that devastated parts of Madagascar. The Tropical Rainfall Measuring Mission satellite (known as TRMM) was placed into service in November of 1997. From its low-earth orbit, TRMM can provide valuable images and information on tropical cyclones around the Tropics using a combination of passive microwave and active radar sensors.

The first image shows Cyclone Nicholas as it was moving to the southwest parallel to the west coast of Australia at 17:17 UTC 17 February (2:17 am 18 February Australian WDT) 2008. The image shows the horizontal pattern of rain intensity within the storm. Rain rates in the center swath are from the TRMM Precipitation Radar (PR), the first precipitation radar in space, while rain rates in the outer swath are from the TRMM Microwave Imager (TMI).

TRMM image of Tropical Cyclone Ivan Credit: Hal Pierce, NASA GSFC/SSAI
> Larger image The rain rates are overlaid on infrared (IR) data from the TRMM Visible Infrared Scanner (VIRS). Nicholas' rain field is asymmetric, which is characteristic of a less intense storm. There is, however, good banding (or curvature) in the rain bands, which is indicative of a developed circulation. At the time of this image, Nicholas was a Category 1 storm with maximum sustained winds estimated at 70 knots (81 mph) by the Joint Typhoon Warning Center. After this image was taken, the system turned south and came ashore near Coral Bay on Australia's remote northwest coast. No damage or injuries were reported due to the storm.

The second image shows cyclone Ivan, a much more powerful storm, as it was bearing down on the island of Madagascar. The image was taken at 06:21 UTC (9:21 am local time) on February 16th. A large, well-defined eye is apparent, and the storm is much more symmetric than was evident with Nicholas. At the time of this image, Ivan was a Category 3 storm with maximum sustained winds estimated at 100 knots (115 mph). It would make landfall the next morning (local time) on the east coast of Madagascar, killing 11. The hardest hit area was the island of Sainte Marie (the small island located just off the main coastline) where 9 people died.

TRMM image of Tropical Cyclone Ivan Credit: Hal Pierce, NASA GSFC/SSAI
> Larger image The last image was taken simultaneously with the previous and shows a 3D picture of Ivan courtesy of the TRMM PR. A ring of taller towers (highlighted in red) reveals areas of deep convection (e.g., thunderstorms) that are associated with the eyewall. The western eyewall is the most prominent in this image. Other areas of deep convection are associated with outer rainbands. The South Indian Ocean typically has 17 tropical cyclones in an average year. So far, there have been 9 tropical systems in the South Indian Ocean this year.

TRMM is a joint mission between NASA and the Japanese space agency JAXA.

Text credit: Steve Lang, NASA's Goddard Space Flight Center/Science Systems and Applications Incorporated


Feb. 20, 2008

Ivan's Remnants Sliding off Madagascar, Fading

Satellite image of fading Tropical Cyclone Ivan Credit: NASA/JPL
> Larger image What was once tropical cyclone Ivan is now a remnant low pressure area, sliding off the island nation of Madagascar.

On Wednesday, February 20, 2008, Ivan's remnant clouds were stretched out over Madagascar and into the southern Indian Ocean. Organized storms always have a circular look to them. Ivan has lost that structure as it continues to dissipate.

This image of Ivan was created on Feb 20 at 10:41 UTC (5:41 a.m. EST) by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite. In the image, Ivan is the elongated purple object stretched over the island of Madagascar.

This AIRS image shows the temperature of the cloud tops or the surface of the Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of Ivan's remnants.

The infrared signal of the AIRS instrument does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of the Earth, revealing warmer temperatures (red).

Text credit: Rob Gutro, NASA's Goddard Space Flight Center


Feb. 14, 2008

Tropical Cyclone Ivan a Category 1

Visible light image of Tropical Cyclone Ivan Credit: NASA/JPL
> Larger image Tropical Cyclone Ivan won't go away. Ivan is still spinning around in the Indian Ocean, and as of Valentine's Day, Feb. 14 at 900 UTC (4:00 a.m. EST). Ivan is a Category 1 cyclone with maximum sustained winds near 65 knots (74 mph).

Ivan is located near 13.5 degrees south latitude and 59.1 degrees east longitude. That's about 515 nautical miles north-northeast of Reunion.

Reunion is an island located in the Indian Ocean. It's located east of Madagascar. Ivan has tracked westward at 9 knots (10 mph) and has intensified. Forecasters agree that Ivan will continue to strengthen as it moves over warm waters.

These two images of Ivan were created on Feb 7 at 9:41 UTC (4:41 a.m. EST) by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite. One image is a visible image, the other is infrared.

Infrared image of Tropical Cyclone Ivan Credit: NASA/JPL
> Larger image The infrared AIRS image shows the temperature of the cloud tops or the surface of the Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of Ivan's clouds.

The infrared signal of the AIRS instrument does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of the Earth, revealing warmer temperatures (red).

Text credit: Rob Gutro, NASA's Goddard Space Flight Center


Feb. 11, 2008

Category 2 Cyclone Ivan in Indian Ocean

AIRS image of Tropical Cyclone Ivan Credit: NASA/JPL
> Larger image Cyclone Ivan is just over the bounds of a Category 2 hurricane, with maximum sustained winds of 85 knots (97 mph) and gusts of 105 knots (120 mph).

At 6:00 Zulu Time (1:00 a.m. EST) on Feb. 11, Ivan was located near 14.2 degrees south latitude and 65.1 degrees east longitude, or 595 nautical miles southwest of Diego Garcia. Ivan was tracking north-northwest at 3 knots (3 mph).

This visible image of Ivan was created on Feb 10 at 2:17 p.m. EST (19:17 UTC) by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite.

Text credit: Rob Gutro, NASA's Goddard Space Flight Center
 
› Back To Top