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Hurricane Season 2010: Tropical Cyclone Gelane (Southern Indian Ocean)
02.22.10
 
February 22, 2010

Gelane is Now a Low Pressure Area Raining on Mauritius

Tropical cyclone Gelane faded into a low pressure area over the weekend after reaching category four cyclone strength last week. The final warning on the storm was issued on Sunday, February 21. It is now bringing some showers to Mauritius.

At 2100 UTC (4 p.m. ET) on Feb. 21, Gelane's maximum sustained winds had weakened to 30 knots (34 mph) and continued weakening through the overnight hours. The storm's last official position was near 20.2 degrees South latitude and 60.5 East longitude, about 170 miles east of Port Louis, Mauritus.

The forecast for today, February 22, from the Mauritius Meteorological Services at 2 p.m. ET said that the low, formerly known as Gelane was about 136 miles (220 kilometers) east-southeast of Mauritius and moving slowly southward. Over the next day, skies will be variably cloudy with some passing showers. Those showers may be more frequent over higher elevations to the east and south. Winds will range from 9-22 mph (15-25 km/hr) with higher gusts. The seas will remain rough, so the public was advised not to venture into the open sea.

Text credit: Rob Gutro, NASA/Goddard Space Flight Center



February 19, 2010

The MODIS instrument on NASA's Aqua satellite caught an impressive visible image of Gelane on February 19. > View larger image
The MODIS instrument on NASA's Aqua satellite caught an impressive visible image of Gelane on February 19 at 09:45 UTC (4:45 a.m. ET) that clearly showed the eye of this Category 4 cyclone.
Credit: NASA MODIS Rapid Response Team
Gelane's eye is visible in this infrared image, and it's surrounded by very high, powerful thunderstorms. > View larger image
The AIRS instrument on NASA's Aqua satellite captured Gelane on Feb. 19 at 4:41 a.m. ET (09:41UTC). Even Gelane's eye is visible in this infrared image, and it's surrounded by very high, powerful thunderstorms with cloud tops as cold as -63F.
Credit: NASA/JPL, Ed Olsen
Small and Mighty Cyclone Gelane Reaches Category Four Strength

NASA satellites monitoring and studying Cyclone Gelane over the last several days have watched the storm become more powerful and more compact. Gelane is now a powerful category four cyclone on the Saffir-Simpson scale. Some regional warnings have been posted for this weekend as the storm approaches.

The Moderate Resolution Imaging Spectroradiometer or MODIS instrument on NASA's Aqua satellite caught an impressive visible image of Gelane on February 19 at 09:45 UTC (4:45 a.m. ET) that clearly showed the eye of this Category 4 cyclone. Additionally, animated multispectral satellite imagery indicates a small 10 nautical mile-round eye. Satellite imagery also helped forecasters determine that the diameter of the storm is about 120-150 nautical miles in diameter.

At this time, Gelane's center remains in the open waters of the Southern Indian Ocean and it is a small storm so hurricane-force winds are not reaching any land areas. At 10 a.m. ET (15:00 UTC) on Friday, February 19, Gelane was 315 miles east-northeast of Port Louis, Mauritius, near 17.3 South and 62.1 East. It had maximum sustained winds near 125 knots (143 mph/231 kph). Hurricane-force winds extended to about 30 miles from the center, while tropical-storm force winds extended 85 miles from the center. The storm is kicking up 29-foot high waves in the open ocean, but residents in nearby Port Louis and Reunion Island will experience rough surf over the weekend as the center of Gelane passes to their east-southeast.

Regional warnings are already in effect. La Reunion island is on "tropical cyclone pre alert." Gelane is far east of the island forecasters believe that it will not get much closer. Meanwhile, residents on the island of Rodrigues are under a tropical cyclone alert category II. The alert means that winds of 120 km/h or higher are likely within 12 to 24 hours. Currently, gusts of up to 90 km/h are forecast. Rodrigues is an island located about 341 miles (550 kilometers) northeast of the island of Mauritius. The island has an area of about 42 square miles (110 square kilometers).

The Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite captured Gelane on Feb. 19 at 4:41 a.m. ET (09:41UTC). Even Gelane's eye was visible in the infrared image. AIRS data showed that Gelane's small 10-mile in diameter center was surrounded by very high, powerful thunderstorms with cloud tops as cold as -63F (-53C).

Gelane was moving south at 7 mph (6 knots/11 km/hr) on Friday, and is forecast to start moving west-southwest this weekend and maintain its slow pace. Over the weekend, Gelane is expected to move into adverse atmospheric conditions (wind shear) and will start weakening.

Text credit: Rob Gutro, NASA/Goddard Space Flight Center



February 18, 2010

TRMM noticed Gelane's eye was much smaller than how it appeared on February 16 at about only 10 nautical miles in diameter. > View larger image
TRMM noticed Gelane's eye was much smaller than how it appeared on February 16 at about only 10 nautical miles in diameter. Heaviest rainfall is in the southwest quadrant of the eye, where rain rates were as high as 2 inches per hour (red).
Credit: NASA/SSAI, Hal Pierce
In a Wink, the TRMM Satellite Sees Gelane's Smaller Eye

The Tropical Rainfall Measuring Mission or TRMM satellite noticed that Tropical Cyclone Gelane's eye is smaller than it was a couple of days ago. TRMM passed over tropical cyclone Gelane in the Southern Indian Ocean early on February 18 and noticed the decrease in size.

TRMM caught Gelane at 09:34 UTC (4:34 a.m. ET). This time the TRMM satellite passed over during the daytime so a visible image from TRMM's VIRS instrument was also used to create a composite satellite image for the TRMM precipitation analysis. TRMM images are created at NASA's Goddard Space Flight Center in Greenbelt, Md. and TRMM is managed by NASA and the Japanese Space Agency, JAXA.

TRMM noticed that Gelane's eye was much smaller than how it appeared in the February 16 image. The eye is now about only 10 nautical miles in diameter. TRMM noticed that the heaviest rainfall now appears in the southwest quadrant of the eye, where rain rates were as high as 2 inches per hour.

At 10 a.m. ET (15:00 UTC) today, February 18, Gelane's maximum sustained winds were near 95 knots with higher gusts. It was about 400 nautical miles northeast of La Reunion Island, near 15.5 South and 62.2 East. It was moving at a slow 5 mph (4 knot) crawl in a south-southeasterly direction.

Gelane is now in an area of moderate vertical wind shear, but is still expected to strengthen a little more before the winds and cooler waters in its path start affecting the storm's strength. The storm is forecast to continue moving south and then south-southeast.

Text credit: Hal Pierce, NASA/SSAI and Rob Gutro, NASA/Goddard Space Flight Center



February 17, 2010

TRMM showed Gelane's heaviest rainfall (in red) of up to 2 inches per hour. > View larger image
TRMM showed that the heaviest rainfall (in red) up to 2 inches per hour, were falling in the western and southern areas of the storm.
Credit: NASA/SSAI, Hal Pierce
The AIRS instrument on NASA's Aqua satellite captured a visible image of Gelane on February 17. > View larger image
The AIRS instrument on NASA's Aqua satellite captured a visible image of Gelane on February 17 at 0953 UTC (4:53 a.m. ET).
Credit: NASA/JPL, Ed Olsen
The cold areas in this image (yellow-green) indicate where there is precipitation or ice in the cloud tops. > View larger image
Data from NASA's Aqua satellite AIRS and AMSU instruments combined on Feb. 17 to make a microwave image of Gelane. The cold areas in this image (yellow-green) indicate where there is precipitation or ice in the cloud tops. The blue areas suggest cold, high thunderstorms.
Credit: NASA/JPL, Ed Olsen
TRMM Saw 16S Explode in Strength as Cyclone Gelane

Tropical Cyclone 16S was a tropical storm yesterday, and today the storm is at Category Two Cyclone (hurricane) strength. NASA satellites have flown over the storm daily and have watched the warm ocean temperatures and light wind shear, allow it to intensify.

On February 16 at 1937 UTC (2:37 p.m. ET) the Tropical Rainfall Measuring Mission (TRMM) satellite passed over powerful tropical cyclone Gelane as it was moving through the open waters of the South Indian Ocean.

TRMM acts as a rain gauge in space and can analyze how much rain is falling in different parts of a tropical cyclone, while the satellite passes overhead in space. To get those rainfall totals, data from several TRMM instruments have to come into play. The rainfall analysis from TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) instruments overlaid on an infrared image from TRMM's Visible and Infrared Scanner (VIRS). TRMM showed that the heaviest rainfall (up to 2 inches per hour) were falling in the western and southern areas of the storm.

When TRMM passed over Gelane, its precipitation radar demonstrated its capability to see through the dense clouds in the center of the cyclone and reveal that Gelane had a well defined eye. Tropical cyclone Gelane was increasing in strength at that time with sustained wind speeds estimated to be over 80 knots (92 mph).

On February 17 at 10 a.m. ET (1500 UTC), Cyclone Gelane's maximum sustained winds were still near 80 knots (92 mph). Because Gelane is a compact storm, those cyclone-force winds extend only 15 miles from the storm's center.

Gelane was about 550 nautical miles northeast of La Reunion Island, near 14.2 South and 61.7 East. Gelane was moving south at 9 mph (8 knots) and generating waves 20 feet high. Gelane is expected to shift its movement to the southeast while still intensifying over the next couple of days.

Data from two instruments on NASA's Aqua satellite were combined on Feb. 17 to make a microwave image of Gelane. Data from the Atmospheric Infrared Sounder (AIRS) was coupled with data from the Advanced Microwave Sounding Unit (AMSU) to create microwave images of storm. 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.

The cold areas in Gelane indicated precipitation or ice in the cloud tops and cold, high thunderstorm tops with heavy rainfall.

Residents of Mauritius, La Reunion and the outlying islands should monitor this storm for possible watches over the next four days.

Text credit: Rob Gutro, NASA/Goddard Space Flight Center





February 16, 2010

Tropical Storm 16S when it was still coming together with strong convection (purple) was flaring up in its center. > View larger image
NASA’s Aqua satellite flew over Tropical Storm 16S on February 15 at 5:05 a.m. ET (1005 UTC) when it was still coming together and noticed that some strong convection (purple) was flaring up in its center.
Credit: NASA/JPL, Ed Olsen
NASA Sees Sixteenth South Indian Cyclone Form

During the early morning hours on Tuesday, February 16, the sixteenth tropical cyclone formed in the South Indian Ocean and NASA captured an infrared image of its cold clouds, watching as it strengthens.

Tropical Cyclone 16S has already powered up into a tropical storm, and is headed in the direction of Port Louis and Reunion Island in the next couple of days.

At 10 a.m. ET (1500 UTC) on February 16, Tropical Storm 16S (TS 16S)) had maximum sustained winds near 52 mph (45 knots). It was about 575 nautical miles north-northeast of La Reunion Island, near 13.1 South and 60.6 East, so it has a good way to go before affecting the island. It was moving south at 9 mph (8 knots).

NASA’s Aqua satellite flew over Tropical Storm 16S on February 15 at 5:05 a.m. ET (1005 UTC) when it was still coming together and noticed that some strong convection was flaring up in its center. Convection is rapidly rising air that creates the thunderstorms that power tropical cyclones. Some of the thunderstorms in TS16S’s center at that time were already very strong, and very high, with cloud top temperatures colder than -63 degrees Fahrenheit!

This morning’s multispectral satellite imagery showed even deeper convection near the low level circulation center in addition to rain bands that are starting to wrap into TS 16’s center.

TS 16S is expected to intensify over the next two days on its southern journey because of low wind shear and warm waters in its path.

Residents of Port Louis, Reunion Island and Mauritius should watch local forecasts and monitor this storm.

Text credit: Rob Gutro, NASA/Goddard Space Flight Center