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Hurricane Season 2008: Tropical Cyclone Gula (Indian)

Feb. 1, 2008

TRMM Captures Twin Cyclones in Southern Indian Ocean

TRMM image of Fame and Gula Credit: Hal Pierce (NASA GSFC/SSAI)
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Two cyclones were captured in close proximity to each other by the Tropical Rainfall Measuring Mission satellite (or TRMM) on two separate occasions: Fame, once a Category 1 cyclone that re-emerged over open water after crossing Madagascar, and Gula, a slightly stronger cyclone passing southward through the east-central portion of the Indian Ocean just east of the island of Mauritius.

The cyclones are visible in the same overpass both times. The first image was taken at 14:43 UTC (6:43 pm local time) Jan. 29, 2008, and shows the horizontal distribution of rain intensity within the two storms. 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).

The rain rates are overlaid on infrared (IR) data from the TRMM Visible Infrared Scanner (VIRS). At the time of this image, Gula in the upper right was a Category 1 storm with maximum sustained winds estimated at 80 knots (92 mph) by the Joint Typhoon Warning Center. It reached a peak intensity of 85 knots after this image was taken. Fame, meanwhile, was a much weaker tropical storm with maximum sustained winds estimated at 35 knots (40 mph). Neither system has a defined eye, nor is very well organized.

TRMM image of Fame and Gula Credit: Hal Pierce (NASA GSFC/SSAI)
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When the circulations of two cyclones come within close proximity to each other, they can interact. One possible interaction is known as the Fujiwara effect, wherein the cyclones begin to circle around one another and draw closer together. Sometimes the stronger circulation can impede or dominate the weaker one and absorb it.

The second image taken two days later at 13:01 UTC (5:01 pm local time) on January 31 shows the centers (denoted by the red symbols) are much closer together. The fact that their orientation relative to one another has also changed in a cyclonic sense indicates that their likely was some interaction between the two storms. Also, both storms have weakened. Fame located on the left has weakened to a tropical depression while Guna has weakened to a tropical storm. Fame caused widespread damage as it passed over Madagascar and is being blamed for 2 deaths there.

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

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

Jan. 31, 2008

Fame is Fleeting; Nearby Gula Heads South

Image of Fame and Gula produced with satellite data Credit: NASA/JPL
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On January 31, forecasters are eyeing two cyclones in the Southern Indian Ocean, Fame and Gula. Gula is located to the northeast of a rapidly weakening Cyclone Fame.

At 12:00 GMT (7 a.m. EST) on Jan. 31, Tropical Cyclone Fame was located approximately 230 nautical miles west-southwest of La Reunion, near 22.7 degrees south latitude and 52.2 east longitude. Fame has tracked west-southwestward recently at 8 knots (9 mph). Fame's winds are down to 35 knots (40 mph), and Fame truly is fleeting.

At the same time, Tropical Cyclone Gula was located near 22.0 degrees south latitude and 58.4 degrees east longitude, or 170 nautical miles east-southeast of La Reunion. Gula is a stronger cyclone than Fame, packing maximum sustained winds of 45 knots (52 mph). Gula is moving faster than Fame, and has tracked south-southwest near 20 knots (23 mph) recently.

Computer models project that Fame will either dissipate or be absorbed into nearby Tropical Cyclone Gula in the next 24 hours.

This image of Fame and Gula was created on Jan. 30 at 21:11 GMT (4:11 p.m. EST) by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite.

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 the storms. Fame is located in the bottom left of the image, and a more well-organized Gula is located in the center of the image, just to the northeast of Fame.

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

Jan. 30, 2008

Tropical Cyclone Gula Raining in the Southern Indian Ocean

Satellite image of Tropical Cyclone Gula Credit: Hal Pierce (SSAI/NASA GSFC)
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Tropical cyclone Gula, also known as 14S was packing maximum sustained winds near 70 knots (80 mph) making it a Category 1 cyclone on the Saffir-Simpson scale. The storm is named after a Babylonian goddess of healing.

On Wednesday, Jan. 30, Gula was located near 16.6 degrees south latitude and 60.0 east longitude, approximately 380 nautical miles northeast of La RĂ©union Island. La RĂ©union is located in the Indian Ocean and is east of Madagascar. Gula has been tracking southward at 6 knots (6 mph).

Images from the Advanced Microwave Sounding Unit (AMSU) instrument on NASA's Aqua satellite have revealed that the system has weakened over the past 12 hours. Forecasters at the Joint Typhoon Warning Center noted that the deepest convection (rapidly rising air that forms clouds and rain) is primarily confined to the northern semi-circle of the storm.

The image above was created from data from the Tropical Rainfall Measuring Mission (TRMM) satellite on Jan. 30 at 12:46 a.m. EST (5:46 UTC). The TRMM image shows the horizontal pattern of rain intensity within the Gula. Gula had moderate rainfall between 35 and 40 millimeters/hour (1.4 to 1.6 inches/hour) in the northwest and southwest quadrants of the storm, as seen in areas of red in this image.

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

Related link:

> NASA's TRMM Web site

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