NASA - National Aeronautics and Space Administration

April 6, 2010

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The MODIS instrument onboard NASA's Aqua satellite captured this visible image of Tropical Storm Robyn on April 5 at 07:35 UTC as it was tracking through the Southern Indian Ocean.
Credit: NASA MODIS Rapid Response Team

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> View larger image AIRS captured in infrared image of Tropical Storm Robyn on April 5 at 07:29 UTC (3:29 a.m. EDT) and there were still some strong, high thunderstorms (purple) to the west of the storm's center. This image clearly shows that Robyn is no threat to any land areas. Credit: NASA/JPL, Ed Olsen NASA's Aqua Satellite Eyes Robyn Flying into History

Robyn is flying into the tropical cyclone history books for this year's Southern Indian Ocean cyclone season. Two instruments on NASA's Aqua satellite caught a glimpse of the storm while flying over it yesterday.

NASA's Aqua satellite is armed with several instruments that provide scientists with data on tropical cyclones. The Moderate Imaging Resolution Spectrometer or MODIS captures high resolution visible and infrared images. The Atmospheric Infrared Sounder or AIRS instrument captures infrared, visible and microwave imagery (coupled with another instrument on Aqua).

AIRS satellite imagery from yesterday, April 5, showed that there were still some high and strong thunderstorms to the west of Robyn's center. The MODIS instrument satellite image also reflects that finding because the higher thunderstorms are visible and appear as of the thunderstorm tops are bubbling up in the west side of the storm.

The Joint Typhoon Warning Center issued their final advisory on Robyn today, April 6 at 09:00 UTC (5 a.m. EDT). At that time, Robyn's maximum sustained winds were down to 39 mph (35 knots) and weakening. It was located about 365 nautical miles southwest of Cocos Island, near 15.5 South and 91.7 East. It is moving north-northwest near 4 mph (3 knots). Robyn has encountered stronger vertical wind shear and will continue to weaken. There is a possibility that the wind shear may weaken and allow Robyn to regenerate. If that happens it would be more appropriate to rename it "Phoenix." Meanwhile, forecasters continue to keep an eye on the system.

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

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April 5, 2010

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NASA's Aqua satellite flew over Tropical Storm Robyn on April 2, 1929 UTC and the AIRS instrument captured an infrared image of the storm's cloud temperatures. The images showed high, cold, thunderstorm cloud tops (purple) as cold as -63F.
Credit: NASA JPL, Ed Olsen Tropical Storm Robyn Nested Away from Land

Tropical Storm "Robyn" didn't have to fly south for the northern hemisphere winter, like the birds (Robins), it formed in the southern hemisphere this past weekend in the Southern Indian Ocean. Infrared satellite imagery from NASA's Aqua satellite revealed that the storm's strong thunderstorms and heavy rainfall are safely "nested" over open waters.

Formerly tropical depression 23S, Robyn strengthened into a tropical storm this weekend. As of Monday, April 5, Robyn had maximum sustained winds near 60 knots (69 mph) gusting to 75 knots (86 mph). It was located about 370 nautical miles southwest of Cocos Islands, Australia, near 16.1 South and 92.0 East. Robyn was moving south-southeast at 7 mph (6 knots) and as it moves it is kicking up waves up to 18 feet high.

The Cocos Islands and Keeling Islands, also called the Territory of Cocos (Keeling) Islands, is an Australian territory. There are twenty-seven coral islands and two atolls in the group of islands.

NASA's Aqua satellite has been flying over Tropical Storm Robyn since it developed on Friday, April 2. The Atmospheric Infrared Sounder (AIRS) instrument captured infrared imagery of the storm that showed high, cold, thunderstorm cloud tops as cold as -63 Fahrenheit (-52 Celsius). That data helped forecasters see that Robyn had powerful rain-making thunderstorms. AIRS provided valuable infrared data on Robyn's cloud top temperatures, which are important because they tell forecasters how high thunderstorms are and the rule is: the higher the thunderstorm, the more powerful the tropical cyclone. AIRS imagery revealed this morning that deep convection (rapidly rising air that condenses and forms thunderstorms that power a tropical cyclone) has decreased. Meanwhile, the low-level center of circulation continues to remain well-organized and the strongest winds are in the southwestern quadrant of the storm.

The Joint Typhoon Warning Center noted that Robyn's movement southeastward is taking the tropical storm further into an area of higher vertical wind shear (which can weaken and tear the storm apart). As a result, Robyn is expected to weaken over the next three days while remaining at sea.

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

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April 2, 2010

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The TRMM satellite passed over Tropical Storm 23S on April 2 at 0913 UTC, and its rainfall was light to moderate (blue-green).
Credit: NASA/SSAI, Hal Pierce Tropical Storm 23S Born in Southern Indian Ocean

According to data from the Tropical Rainfall Measuring Mission, or TRMM satellite mostly light to moderate rain is falling in the latest tropical cyclone born in the waters of the Southern Indian Ocean. TRMM can measure rainfall from its vantage point in space as it orbits the Earth and forecasters will be using TRMM data to continue monitoring the storm's intensity.

Tropical Storm 23S was born today, April 2 about 260 nautical miles west of Cocos Island, Australia, near 11.5 South and 92.5 East. It has maximum sustained winds of 39 mph (35 knots) and is moving southward at around 6 mph (5 knots). Although Cocos Island is not in the direct path of the storm, it was being affected with by thunderstorms in the storm's outer bands.

When the TRMM satellite passed over Tropical Storm 23S on April 2 at 0913 UTC (5:13 a.m. EDT) it measured light to moderate rainfall. Since then, infrared satellite imagery indicated that bands of thunderstorms have consolidated around the center of 23S's center of circulation. Rainfall is likely going to intensify in the system as it strengthens over the weekend. At times rain may be falling in some areas of the storm at up to 2 inches per hour.

Over the weekend, 23S is forecast to track south and intensify, according to the Joint Typhoon Warning Center. By Monday, 23S will run into a mid-latitude trough, or extended area of low pressure that will weaken it.

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