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Tropical Storm Emang (Southern Indian Ocean)
01.17.13
 
MODIS image of Emang› Larger image
NASA's Aqua satellite passed over Tropical Storm Emang on Jan. 17 at 0812 UTC (3:12 a.m. EST) and captured this infrared image of the storm. The strongest storms are southwest of the center (where the two areas of brightest white clouds appear). Credit: NASA Goddard MODIS Rapid Response Team
NASA Sees Tropical Storm Emang Unraveling

As Tropical Storm Emang appeared to be unraveling in the Southern Indian Ocean, NASA's Aqua satellite passed overhead and captured an infrared look at the dying storm.

NASA's Aqua satellite passed over Tropical Storm Emang on Jan. 17 at 0812 UTC (3:12 a.m. EST) and the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument captured an infrared image of the storm. The MODIS image showed two areas of strongest convection and thunderstorms, both southeast of the center of circulation. The low-level center of the storm was fully exposed to outside winds. Satellite imagery also showed that the storm has been elongating, and whenever a storm becomes "stretched out" it weakens the circulation, just as a flat tire cannot rotate well.

An earlier satellite overpass of Emang showed shallow (weak) banding of thunderstorms in the southeastern quadrant when NASA's Tropical Rainfall Measuring Mission satellite passed overhead at 0607 UTC (1:07 a.m. EST).

The Joint Typhoon Warning Center (JTWC), the organization that forecasts tropical cyclones in the Southern Indian Ocean and other oceans, issued their final bulletin on Emang on Jan. 17 at 0900 UTC (4 a.m. EST). At that time, Emang's maximum sustained winds were near 35 knots (40 mph/64.8 kph). Emang's center is located near 14.9 south latitude and 75.2 east longitude, about 510 nautical miles (586.9 miles/944.5 km) southeast of Diego Garcia. Emang is moving slowly to the west-southwest at 7 knots (8 mph/ 13 kph).

The JTWC noted that Emang is located under convergent upper-level flow. That means that air is coming together in the upper atmosphere and being pushed downward to the lower level of the atmosphere, which is preventing air at the surface to rise, condense and form more thunderstorms to keep Emang going (because a tropical cyclone is made up of hundreds of thunderstorms).

The JWTC expects Emang to dissipate by Jan. 18 over open ocean.

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



Jan. 16, 2013

TRMM image of Emang› Larger image
On Jan. 16 at 0702 UTC (2:02 a.m. EST) NASA's TRMM satellite saw mostly moderate rain (in green) in Tropical Storm Emang. There was one small area of heavy rainfall (red) near the center. Credit: SSAI/NASA, Hal Pierce
NASA Sees One Area of Strength in Tropical Storm Emang

Tropical Storm Emang continues to move through open waters in the Southern Indian Ocean and NASA's TRMM satellite noticed one area of heavy rainfall near the center.

On Jan. 16 at 0702 UTC (2:02 a.m. EST) NASA's Tropical Rainfall Measuring Mission (TRMM) satellite passed over Emang, and captured rainfall rates. TRMM identified that moderate rain was falling throughout most of the tropical cyclone, and heavy rainfall was occurring near the storm's center. TRMM estimated the heavy rain falling at a rate of 2 inches (50 mm) per hour.

On Jan. 16 at 0900 UTC (4 a.m. EST), Tropical Storm Emang had maximum sustained winds near 35 knots (40 mph/64.8 kph). Emang was located near 14.2 south latitude and 77.7 east longitude, about 580 nautical miles (667.5 miles/1,074 km) southeast of Diego Garcia. Emang is moving slowly to the west at 3 knots (3.4 mph/5.5 kph). Emang is currently not a threat to any land areas.

Emang is expected track west-southwest and may affect La Reunion Island by Jan. 21. However, as it tracks west, after briefly intensifying, wind shear and cooler water temperatures are expected to weaken the storm.

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



AIRS image of Emang› Larger image
NASA infrared data on Tropical Storm Emang captured by NASA's Aqua satellite on Jan. 15 at 0823 UTC (3:23 a.m. EST) showed that the largest area of powerful thunderstorms (purple) were in the northern half of the storm. That are is where heaviest rain was falling. Credit: NASA JPL, Ed Olsen
Infrared NASA Imagery Shows Sinking Air, Elongation in Tropical Storm Emang

The Atmospheric Infrared Sounder instrument that flies on NASA's Aqua satellite provides valuable data to tropical cyclone forecasters, and revealed sinking air, a small area of powerful thunderstorms, and a slightly elongated Tropical Storm Emang.

Infrared data on Tropical Storm Emang's cloud top temperatures was captured by the Atmospheric Infrared Sounder (AIRS) instrument on Jan. 15 at 0823 UTC (3:23 a.m. EST). AIRS data showed that the largest area of powerful thunderstorms were in the northern half of the storm. That area showed cold cloud top temperatures of -63F (-52C) indicating high, powerful thunderstorms where the heaviest rain was falling.

The AIRS data also showed that sinking air or subsidence was occurring in the southwestern quadrant of the storm, which is weakening the convection there.

AIRS data also showed that the low level center of circulation had become slightly elongated, stretching from southwest to northeast. For a tropical cyclone to intensify, its circulation centers from the surface to upper atmosphere basically have to stack up. When the center becomes elongated the storm usually has a difficult time intensifying.

On Jan. 15 at 0900 UTC, Tropical Storm Emang's maximum sustained winds were near 35 knots (40.2 mph/64.8 kph). Emang is moving slowly to the south-southwest at 4 knots (4.6 mph/7.4 kph). Emang was centered near 13.5 south latitude and 78.6 east longitude, about 525 nautical miles (604.2 miles/ 972.3 km) southeast of Diego Garcia. Diego Garcia is a coral atoll in the central southern Indian Ocean.

Forecasters at the Joint Typhoon Warning Center expect atmospheric conditions to improve over the coming days, so that Emang can organize and strengthen. Fortunately, the storm is no threat to land.

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



Jan. 14, 2013

TRMM image of Emang› Larger image
NASA's TRMM satellite captured rainfall rates in Tropical Storm Emang on Jan. 13 at 0404 UTC. Moderate (green) and heavy rainfall (red) was occurring around the center of circulation, where rainfall rates ranged from 30 mm (1.18 inches) to 50 mm (2 inches) per hour. Credit: NASA/SSAI Hal Pierce
NASA Sees Strength in Newborn Tropical Cyclone Emang

Tropical Cyclone Emang developed in the Southern Indian Ocean on Sunday, Jan. 13 about 525 nautical miles east-southeast of Diego Garcia. At that time, infrared satellite imagery revealed that the low level circulation center was partially exposed to outer winds, and there was a burst of thunderstorm development over the northwestern quadrant.

NASA's Tropical Rainfall Measuring Mission (TRMM) satellite captured rainfall rates in Tropical Storm Narelle on Jan. 13 at 0907 UTC (5:07 a.m. EST). Moderate and heavy rainfall was occurring around the center of circulation, where rainfall rates ranged from 30 mm (1.18 inches) to 50 mm (2 inches) per hour. That heavy rainfall is a sign that there is strong convection occurring within the storm, and forecasters at the Joint Typhoon Warning Center expect the storm will consolidate and organize more over the coming week.

On Monday, Jan. 14, at 0900 UTC (4 a.m. EST), Emang's maximum sustained winds were near 35 knots (40 mph/64.8 kph). Emang's center moved near 12.5 south latitude and 79.4 east longitude, about 500 nautical miles (575.4 miles/ 926 km) southeast of Diego Garcia. Emang was moving to the southwest at just 3 knots (3.4 mph/5.5 kph). Emang is located in is a weak steering environment. It is moving slowly under the influence of a building subtropical ridge (elongated area) of high pressure located to the south of the storm.

Monday's satellite data showed that the low-level center had now become fully exposed to outside winds, and there were shallow bands of thunderstorms around the northwestern edge of the storm. Emang is currently being battered with moderate (up to 20 knots/23 mph/37 kph) vertical wind shear.

Forecasters at the Joint Typhoon Warning Center expect improvements in environmental conditions which will improve the storm's organization. Emang is expected to slowly intensify over the next couple of days as it travels over open ocean. By the end of the week, Emang is expected to reach peak intensity as a cyclone of 65 knots (74.8 mph/120.4 kph).

Emang is currently not a threat to any land areas.

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