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Tropical Storm 18S (Southern Indian Ocean)
03.01.13
 
MODIS image of 18S› Larger image
The MODIS instrument aboard NASA's Aqua satellite captured this infrared image of the remnants of Tropical Storm 18S on March 1 at 0615 UTC (1:15 a.m. EST). Some strong thunderstorms (bright white areas, bottom of image) were developing south of the center. Credit: NRL/NASA
NASA's Aqua Satellite Sees a Fighter in Cyclone 18S Remnants

The remnants of Cyclone 18S continue their struggle for survival in the environment of the Southern Indian Ocean, and NASA's Aqua satellite saw some signs of strength on March 1. Wind shear continues to prevent the low from strengthening.

When NASA's Aqua satellite passed over the remnants of Cyclone 18S on March 1 at 0615 UTC (1:15 a.m. EST), the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument's captured an infrared view of the storm that revealed some areas of powerful convection. Convection is rising air that helps form the thunderstorms that make up a tropical cyclone. MODIS imagery showed several areas south of the center of circulation where thunderstorms were flaring.

On March 1, Tropical Cyclone 18S's (18S) remnants had maximum sustained winds near 25 knots (28.7 mph/46.3 kph) and a minimum central pressure near 1003 millibars. 18S was centered near 14.2 south latitude and 101.4 east longitude in the Southern Indian Ocean. That's about 290 nautical miles (333.7 miles/ 537.1 km) east-southeast of Cocos Island.

Wind shear has been the foe of Tropical Cyclone 18S since it formed, and continued to be one on March 1. The Joint Typhoon Warning Center (JTWC) indicated that 18S is still in an area of moderate to strong easterly vertical wind shear blowing between 20 and 30 knots (23 mph to 34 mph/37 kph to 64.7 kph). As a result of the wind shear, 18S has a low chance of consolidating into a tropical depression over the next day or two.

Text Credit: Rob Gutro
NASA's Goddard Space Flight Center, Greenbelt, Md.


February 28, 2013

AIRS image of 18S› Larger image
NASA's Aqua satellite captured an image of the remnant low pressure area at 0710 UTC (2:10 a.m. EST) on Feb. 28 and showed that the strongest thunderstorms were on the western side of the center. Credit: NRL/NASA
NASA Sees Remnants of Cyclone 18S Still Struggling

NASA's Aqua satellite passed over the remnants of Tropical Storm 18S on Feb. 28, and imagery indicated hat it was still battling wind shear.

On Feb. 28, the remnant low pressure area appeared to have a stronger circulation in a visible image from NASA's Aqua satellite. The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument captured an image of the remnant low at 0710 UTC (2:10 a.m. EST). The center was located near 15.1 south latitude and 99.7 east longitude, about 240 nautical miles (276.2 miles/444.5 km) southeast of the Cocos Islands in the Southern Indian Ocean. The MODIS image showed that convection (rising air that creates thunderstorms that make up the storm) had increased in the western half of the storm within the last day. Although thunderstorms are re-developing, they continue to be pushed to the western side of the storm because of easterly wind shear.

The storm is facing two factors that are preventing it from reorganizing: cool waters and wind shear. Because sea surface temperatures are just below 80 degrees Fahrenheit (26.6 Celsius), development is being hindered. Vertical easterly wind shear of up to 20 knots (23 mph/37 kph) is also preventing the storm from redeveloping. On Feb. 28, the Joint Typhoon Warning Center gave the remnants of 18S a low chance of reorganizing in the next day or two.

Text Credit: Rob Gutro
NASA's Goddard Space Flight Center, Greenbelt, Md.


February 27, 2013

MODIS image of 18S› Larger image
This infrared image of Tropical Depression 18S was captured on Feb. 27 at 15:52 UTC (10:52 a.m. EST) by the Moderate Resolution Imaging Spectroradiometer or MODIS instrument that flies aboard NASA's Terra satellite. Wind shear has pushed the bulk of 18S's rainfall to the west. Credit: NASA/NRL
NASA's Terra Satellite Sees Demise of Tropical Depression 18S

Wind shear has been battering Tropical Storm 18S since it was born, and today it weakened to a remnant low pressure area in the Southern Indian Ocean. NASA's Terra satellite captured an infrared image of the depression that showed strong wind shear had pushed the bulk of rain to the west of the system's center.

The Moderate Resolution Imaging Spectroradiometer or MODIS instrument that flies aboard NASA's Terra satellite captured an infrared image of 18S's remnants on Feb. 27 at 15:52 UTC (10:52 a.m. EST). The image, which shows temperatures based on the shades of white (bright white is coldest), provided a clear picture of the strong easterly wind shear battering the tropical cyclone. The clouds that appear brightest white in the image are the coldest and highest cloud tops and strongest thunderstorms associated with the depression. Those powerful thunderstorms were being pushed west of the center of Tropical Depression 18S. The lower, warmer clouds circling center of circulation took on a ghostly appearance in the infrared image.

At 1552 UTC (10:52 a.m. EST) on Feb. 27, the remnants of Tropical Depression 18S had maximum sustained winds near 30 knots (34 mph/64.7 kph). It was located near 15.5 degree south latitude and 98.8 east longitude. Tropical Depression 18S had a minimum central pressure of 1000 millibars.

According to the Joint Typhoon Warning Center (JTWC) an analysis of the upper level winds showed that the tropical storm was still in an area of strong (30-40 knot/34.5 to 46.0 mph/55.5 to 74.0 kph) easterly vertical wind shear. Moderate wind shear is expected to continue in the vicinity of the remnant low pressure area for another day.

Text Credit: Rob Gutro
NASA's Goddard Space Flight Center, Greenbelt, Md.


February 26, 2013

AIRS image of 18S› Larger image
An infrared look at Tropical Storm 18S by the AIRS instrument on NASA's Aqua satellite on Feb. 26, revealed wind shear continues to take its toll on the storm and keeps pushing its strongest (purple) precipitation away from the center of the storm. Credit: NASA JPL, Ed Olsen
NASA Infrared Data Shows Tropical Cyclone 18S Still Battling Wind Shear

An infrared look at Tropical Storm 18S by NASA's Aqua satellite revealed wind shear continues to take its toll on the storm and keeps pushing its main precipitation away from the center of the storm.

Wind shear is a major factor that can keep a tropical cyclone "down" or unable to consolidate and intensify because it keeps pounding the circulation of winds head on. Strong wind shear has been battering Tropical Cyclone 18S for a couple of days and is expected to continue the next couple of days.

On Feb. 26 at 1500 UTC (10 a.m. EST) Tropical Storm 18S was located about 1,000 nautical miles (1,151 miles/1,852 km) west-northwest of Learmonth, Australia, near 15.5 south and 98.0 east. TS18S still had maximum sustained winds near 35 knots (40.2 mph/64.8 kph) and was now moving to the south-southeast near 4 knots (4.6 mph/7.4 kph).

Satellite imagery shows that the main convection and thunderstorms are still being pushed away from the center of circulation from wind shear. Vertical wind shear has also caused the storm to stretch out making it difficult to find the center on satellite imagery. According to the Joint Typhoon Warning Center (JTWC), an analysis of the upper level winds showed that the tropical storm is in an area of strong (30-40 knot/34.5 to 46.0 mph/55.5 to 74.0 kph) easterly vertical wind shear.

Tropical Storm 18S is expected to drift under weak steering conditions for the next two days after which time another weather system will push the storm eastward toward Western Australia.

Text Credit: Rob Gutro
NASA's Goddard Space Flight Center, Greenbelt, Md.


February 25, 2013

AIRS image of 18S› Larger image
On Feb. 24 at 2:29 a.m. EST the AIRS instrument aboard NASA's Aqua satellite captured infrared data on TS18S. The coldest temperatures (purple) and highest cloud tops (and strongest thunderstorms) appeared in a large area around TD18S's center. Credit: NASA/JPL, Ed Olsen
NASA Spots Active Southern Indian Ocean's Tropical Storm 18S

The eighteenth tropical cyclone of the Southern Indian Ocean season formed over the weekend of Feb. 23-24 along with Cyclone Rusty as Cyclone Haruna crossed southern Madagascar. NASA's Aqua satellite measured Tropical Storm 18S' cloud top temperatures and saw powerful thunderstorms around the storm's core.

Cyclone Rusty is nearing a landfall in northwestern West Australia, while Tropical Storm 18S is headed in a similar direction.

Tropical Storm 18S (TS18S) was born on Feb. 24 and achieved tropical storm strengthe with maximum sustained winds near 35 knots (40 mph). It formed about 45 nautical miles southeast of the Cocos Islands, Australia near 12.7 south latitude and 97.3 east longitude.

Wind shear on Feb. 24 was affecting the storm, and pushing the strongest thunderstorms west of the center. NASA's TRMM satellite captured data on rainfall and noted the strongest rainfall was occurring west of the center at a rate of more than 1.4 inches per hour.

On Feb. 24 at 0729 UTC (2:29 a.m. EST), the Atmospheric Infrared Sounder (AIRS) instrument aboard NASA's Aqua satellite captured infrared data on TS18S. The data was created into a false-colored image at NASA's Jet Propulsion Laboratory in Pasadena, Calif. False coloration enables meteorologists to see distinction in temperatures, and the coldest temperatures and highest cloud tops (and strongest thunderstorms) appeared in a large area around TD18S's center. Cloud top temperatures around the center exceeded the -63 Fahrenheit (-52 Celsius) threshold, indicating that those areas were likely dropping heavy rainfall.

Satellite data has shown that wind shear is still affecting the tropical storm, and pushing the main convection to the west. That wind shear is expected to persist over the next couple of days before easing up.

On Feb. 25 at 1500 UTC (10 a.m. EST) Tropical Storm 18S was located about 980 nautical miles (1,128 miles/1,815 km) west-northwest of Learmonth, Australia, near 14.7 south and 99.0 east. TS18S had maximum sustained winds near 35 knots (40.2 mph/64.8 kph) and was moving to the southeast near 6 knots (6.9 mph/11.1 kph).

Forecasters at the Joint Typhoon Warning Center expect TS18S to take an easterly track, toward Port Hedland and Learmonth, Western Australia after the second of March. If that occurs, the residents of northwestern Australia will be recovering from Cyclone Rusty when Tropical Storm 18S approaches.

Text Credit: Rob Gutro
NASA's Goddard Space Flight Center, Greenbelt, Md.