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Hurricane Season 2008: Nicholas (Indian Ocean)
02.15.08
 


Feb. 21, 2008

Active Cyclones in the South Indian Ocean

TRMM image of Tropical Cyclone Nicholas Credit: Hal Pierce, NASA GSFC/SSAI
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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
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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
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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

Nicholas Fading Near Far Western Australian Coast

Image of remnants of Tropical Cyclone Nicholas Credit: NASA/JPL
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Tropical Cyclone Nicholas is fading near the western Australian coast, and the Joint Typhoon Warning Center (JTWC) has just issued their final advisory on it.

On Feb. 20 at 1500 UTC (10:00 a.m. EST), Nicholas was near 25.9 degrees south latitude and 114.3 degrees east longitude. It's approximately 205 nautical miles south of Learmonth, Australia. Over the past 6 hours, Nicholas has tracked south-southeastward at 12 knots (13 mph). The storm has maximum sustained winds near 25 knots (29 mph).

The JWTC noted that "The system continues to weaken due to land interaction and moderate vertical wind shear. Based upon satellite intensity estimates, as well as synoptic observations, the storm is now below warning criteria." The remnants are expected to continue to track generally in a southerly direction over the next 12 hours. The low-level remnant circulation will remain near the western Australian coast as it tracks southward, but regeneration is not expected because of cooler sea surface temperatures and wind shear (winds that tear a storm apart).

This visible image of Nicholas was created on Feb 20 at 5:41 UTC (12:41 a.m. EST) by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite. Nicholas is visible as the swirl of clouds on the left side of the image, and Australia is the green landmass to the right of the storm.

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



Feb. 15, 2008

Cyclone Nicholas Headed for Landfall in Western Australia

AIRS image of Tropical Cyclone Nicholas Credit: NASA/JPL
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Tropical Cyclone Nicholas is forecast to make landfall in Western Australia over the weekend of Feb. 16.

On Feb. 15, Nicholas was in the southern Indian Ocean, with maximum sustained winds near 70 knots and higher gusts. Nicholas was moving west-southwest near 6 knots (6 mph). At 1200 UTC (7:00 a.m. EST), Nicholas was near 16.4 degrees south latitude, and 118.8 degrees east longitude, or 440 miles northeast of Learmonth, Australia. Satellite imagery indicates that Nicholas is a well-developed storm.

Forecasters expect Nicholas' track to shift to the southwest, and it is expected to make landfall 100 miles west of Port Hedland, on Feb. 17.

Cyclone Nicholas is visible as the circular purple and blue area to the northwest of Australia (top left) in this infrared image. The image was created by data from the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite on Feb. 15 at 5:23 UTC (12:53 a.m. EST).

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 Nicholas. The infrared signal 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