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Tropical Cyclone Imelda (Southern Indian Ocean)
04.16.13
 
MODIS image of Imelda› Larger image
NASA's Aqua satellite passed over Tropical Cyclone Imelda on April 16 at 0943 UTC (5:43 a.m. EDT). Aqua captured this visible image that clearly showed the center of circulation, and most of the precipitation southeast of the center. Credit: NASA/NRL
NASA Imagery Shows Wind Shear Hammering Cyclone Imelda

Cyclone Imelda has lost both her punch and her hurricane status as the storm moved into an area of higher wind shear and cooler waters in the Southern Indian Ocean. NASA’s Aqua satellite provided an image of Imelda that showed wind shear that has been hammering the storm, had pushed the bulk of the storm’s precipitation southeast of the center.

Wind shear at higher levels has increased to as high as 30 knots (34.5 mph/55.5 kph), according to upper level analysis of the atmosphere that was conducted by the Joint Typhoon Warning Center. That stronger wind shear is weakening Imelda quickly.

NASA's Aqua satellite passed over Tropical Cyclone Imelda on April 16 at 0943 UTC (5:43 a.m. EDT) and the Moderate Resolution Imaging Spectroradiometer instrument captured a visible image of the storm that clearly showed most of the precipitation had been pushed southeast of the center from wind shear. Animated multispectral satellite imagery showed that the low level circulation center was fully exposed and there was no deep convection or strong thunderstorms developing over the previous 12 hours.

The last official warning on Imelda was issued on April 16 at 0900 UTC (5 a.m. EDT), when Imelda’s maximum sustained winds had fallen to 35 knots (40 mph/65 kph). The weakening tropical storm was located near 21.2 south and 62.9 east, about 410 nautical miles (471.8 miles/ 759.3 km) east of La Reunion island and moving to the southeast at 5 knots (5.7 mph/9.2 kph).

Imelda is expected to continue weakening and should dissipate in the next day or two.

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



April 15, 2013

MODIS image of Imelda› Larger image
NASA's Aqua satellite passed over Tropical Cyclone Imelda on April 14 at 5:55 a.m. EDT. Aqua captured this visible image that clearly shows the eye of the storm. La Reunion Island is left of the storm. Credit: NASA Goddard MODIS Rapid Response Team

MODIS image of Imelda› Larger image
NASA's Aqua satellite passed over Tropical Cyclone Imelda on April 15 at 2:15 a.m. EDT. Aqua captured this visible image that showed Imelda’s eye had filled in with clouds and the storm appears to be elongating. Credit: NASA Goddard MODIS Rapid Response Team
Cyclone Imelda’s Eye Opens and Closes for NASA’s Aqua Satellite

Cyclone Imelda reached hurricane strength on April 14 and its eye “opened” and became apparent on visible imagery on imagery from NASA’s Aqua satellite. By April 15, the eye had “closed” and become filled in with clouds.

When NASA's Aqua satellite passed over Tropical Cyclone Imelda on April 14 at 0955 UTC (5:55 a.m. EDT), the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard captured a visible image that clearly showed the eye of the storm. The image was created by the MODIS Rapid Response Team at NASA’s Goddard Space Flight Center in Greenbelt, Md.

On April 15 at 0615 UTC (2:15 a.m. EDT), MODIS captured another image of Imelda and the storm’s eye appeared “closed.” The eye had actually become filled in with a large cold dense overcast (clouds). The storm also appeared to be somewhat elongated from west to east.

On April 15 at 0900 UTC (5 a.m. EDT), Imelda’s maximum sustained winds were near 65 knots (75 mph/120.4 kph). Imelda’s center was located near 19.8 south latitude and 61.9 east longitude, about 360 nautical miles (414.3 miles/666.7 kph) east-northeast of La Reunion Island. Imelda is moving south at 9 knots (10.3 mph/ 16.6 kph).

Microwave satellite imagery from the AMSU-B instrument on NOAA’s polar orbiting satellite showed that the convection around the low-level center is weakening. Forecasters at the Joint Typhoon Warning Center expect that Imelda will continue to weak as wind shear continues to increase (which is causing the storm to elongate).

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








April 12, 2013

MODIS image of Imelda› Larger image
NASA's Aqua satellite passed over Tropical Cyclone Imelda on April 12 at 1010 UTC (6:10 a.m. EDT). The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard Aqua captured this visible image that showed the strongest thunderstorms and most of the precipitation east of the center. Credit: NASA Goddard MODIS Rapid Response Team
NASA Satellite Imagery Shows Cyclone Imelda One-Sided

An upper-level low pressure system is sapping the cloud and thunderstorm development on the western side of Cyclone Victoria in the Southern Indian Ocean. New NASA satellite imagery showed that the bulk of rainfall was located east of the storm’s center.

At 0900 UTC (5 a.m. EDT) on April 12, Tropical Cyclone Imelda was tropical storm strength with maximum sustained winds near 45 knots (51.7 mph/83.3 kph). Imelda was centered near 14.1 south latitude and 58.9 east longitude, about 465 miles north-northeast of La Reunion Island. Imelda is moving to the south-southeast at 6 knots (7 mph/11.1 kph) and away from La Reunion.

NASA's Aqua satellite passed over Tropical Cyclone Imelda on April 12 at 1010 UTC (6:10 a.m. EDT). The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard Aqua captured a visible image that showed the strongest thunderstorms and most of the precipitation east of the center. Imelda’s center of circulation was also easily seen on satellite imagery, and the center is now fully exposed.

So what’s causing the suppression of clouds? An upper-level trough (elongated area) of low pressure moving in from the west is extending over the storm and causing subsidence, or the sinking of air. To maintain a tropical cyclone, air needs to rise to form clouds and thunderstorms. When air sinks to the surface clouds are unable to form.

Forecasters at the Joint Typhoon Warning Center (JTWC) issued a bulletin about Imelda at 0900 UTC (5 a.m. EDT) that noted the environment Imelda is moving through has become increasingly unfavorable to maintain the tropical cyclone and forecasts Imelda gradually dissipating over the next three days.

April 11, 2013

MODIS image of Imelda› Larger image
NASA's Aqua satellite passed over Tropical Cyclone Imelda on April 11 at 0925 UTC (5:25 a.m. EDT). The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard Aqua captured this visible image that showed a well-developed Tropical Cyclone Imelda in the Southern Indian Ocean. Credit: NASA Goddard MODIS Rapid Response Team

AIRS image of Imelda› Larger image
This infrared image taken from the AIRS instrument aboard NASA's Aqua satellite on April 10 at 0923 shows that the strongest convection and thunderstorms (purple) have been pushed east of center from wind shear. Credit: NASA JPL, Ed Olsen
Cyclone Imelda Turned the Corner on NASA Satellite Imagery

An area of low pressure moving toward Cyclone Imelda from the west has turned the storm to the south from its westward track, as NASA’s Aqua satellite passed overhead and captured a visible and an infrared image of the powerful storm that showed the effects of wind shear.

NASA's Aqua satellite passed over Tropical Cyclone Imelda on April 11 at 0925 UTC (5:25 a.m. EDT). The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard Aqua captured a visible image that showed a well-developed Tropical Cyclone Imelda in the Southern Indian Ocean that has now turned to the south. The MODIS image shows tightly-curved, powerful bands of thunderstorms stretching from the north to the east and south of the center of circulation, all wrapping into the center. MODIS imagery was created by the MODIS Rapid Response Team at NASA’s Goddard Space Flight Center in Greenbelt, Md.

At the same time, the Atmospheric Infrared Sounder (AIRS) instrument that flies with MODIS aboard Aqua, captured an infrared image of Imelda. The image showed that the strongest convection and thunderstorms had been pushed east of center from wind shear. Those powerful thunderstorms had cloud top temperatures colder than -63 Fahrenheit (-52 Celsius), and were dropping heavy rainfall. The AIRS image was created at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Microwave satellite imagery indicated that the strongest convection and most powerful thunderstorms are occurring in the storm’s eastern quadrants as a result of an increase in wind shear. Powerful thunderstorms are also occurring over the center of circulation.

On April 11 at 0900 UTC (5 a.m. EDT), Cyclone Imelda had maximum sustained winds near 75 knots (80.5 mph/129.6 kph). Imelda is located near 13.1 south latitude and 57.9 east longitude, about 515 nautical miles (593 miles/954 km) north-northeast of La Reunion. Since interacting with the approaching area of low pressure from the west and then turning south, Imelda has slowed down, and is moving at just 2 knots (2.3 mph/3.7 kph).

The Joint Typhoon Warning Center forecasters expect Imelda to continue tracking generally southward over the next two days and then shift to the southeast as it starts moving around the edge of a ridge of high pressure.

The sea surface temperatures in the vicinity are still quite warm, between 28 and 29 Celsius (82.4 and 84.2 Fahrenheit) which forecasters believe may help Imelda strengthen a little more over the next two days. After that time, wind shear is expected to increase and quickly weaken the storm.

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



April 10, 2013

AIRS image of Imelda› Larger image
This infrared image of Cyclone Imelda was captured on April 9 at 0935 UTC (5:35 a.m. EDT) by the AIRS instrument that flies aboard NASA's Aqua satellite. The areas of purple indicate strong thunderstorms with heavy rainfall, whose cloud top temperatures are as cold as -63F/-52C. Credit: NASA JPL, Ed Olsen
NASA Infrared Image Identifies Several Areas of Power in Cyclone Imelda

Cyclone Imelda has continues to strengthen, and infrared NASA satellite imagery indicated powerful convection throughout the storm.

Infrared satellite imagery indicates cloud top temperatures, and the colder the temperatures, the higher the cloud top is in the troposphere. Higher cloud tops indicate stronger uplift in the air, and that means stronger thunderstorms can develop. When NASA's Aqua satellite passed over Cyclone Victoria on April 9 at 0935 UTC (05:35 a.m. EDT), the Atmospheric Infrared Sounder instrument captured infrared data on the strengthening cyclone.

On April 10 at 0900 UTC (5 a.m. EDT), Imelda's maximum sustained winds were near 70 knots (80.5 mph/129.6 kph), making it a category one Cyclone. Imelda was centered near 12.1 south latitude and 58.2 east longitude, about 570 nautical miles north-northeast of La Reunion. Imelda is moving to the west-southwest at 4 knots (4.6 mph/7.4 kph) and has slowed in forward movement.

Imelda is moving around the northwestern edge of a ridge (elongated area) of high pressure and is in an area of light wind shear. A trough of low pressure is expected to push Imelda to the southeast.

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



April 09, 2013

NASA Sees Heaviest Rain on Cyclone Imelda's Western Side

TRMM image of Imelda› Larger image
The TRMM satellite captured rainfall rates in Cyclone Imelda on April 8, 2013 at 0447 UTC. The most powers storms were on the western side of the storm dropping rain a rate of over 86mm/hr (~3.4 inches) (in red). Credit: NASA/SSAI, Hal Pierce

TRMM image of Imelda› Larger image
TRMM showed that some powerful thunderstorms on Imelda's western side reached 9.3 miles high. Credit: NASA/SSAI, Hal Pierce
Tropical Cyclone Imelda's heaviest rainfall is occurring on its western side according to precipitation data obtained from NASA's Tropical Rainfall Measuring Mission (TRMM) satellite as it passed overhead on April 8.

The TRMM satellite flew directly over an intensifying tropical cyclone called Imelda in the South Indian Ocean on April 8, 2013 at 0447 UTC (12:47 a.m. EDT). The rainfall analysis used data collected with TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) instruments. The analysis showed a large area of rainfall on the western side of the developing tropical cyclone. TRMM PR found that some powerful convective storms in that area were dropping rain a rate of over 86 mm (~3.4 inches) per hour.

TRMM's Precipitation Radar (PR) can be used to provide vertical profiles of rain from the surface up to a height of about 12 miles (20 kilometers). At NASA's Goddard Space Flight Center in Greenbelt, Md. a 3-D image of tropical cyclone Imelda was created using TRMM PR data that showed some thunderstorms west of Imelda's center of circulation towered to heights of above 15 kilometers (~9.3 miles).

At 0900 UTC (5 a.m. EDT) on April 9, Imelda's maximum sustained winds had increased to 50 knots (57.5 mph/92.6 kph). Imelda was centered near 11.6 south latitude and 61.2 east longitude, about 490 nautical miles (564 miles/907.5 km) west-southwest of Diego Garcia. Imelda was moving to the west-southwest near 13 knots 14.9 mph/24.8 kph). Satellite data on April 9 noticed the beginning of an eye-like feature forming, indicating that the storm continues to intensify.

Imelda is no threat to any land areas. It is expected to continue moving west before turning to the southeast as a result of a low pressure area moving toward it from the west. The Joint Typhoon Warning Center expects the storm to strengthen to hurricane strength over the next several days.

Text Credit: Hal/PierceRob Gutro
NASA's Goddard Space Flight Center, Greenbelt, Md.

TRMM Flyby of Tropical Cyclone Imelda on April 8, 2013. Credit: NASA



April 08, 2013

NASA Sees Cyclone Imelda Getting Wound Up

MODIS image of Imelda› Larger image
NASA's Aqua satellite passed over Tropical Storm Imelda on April 8 at 0605 UTC (2:05 a.m. EDT). The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard Aqua captured a visible image of Tropical Cyclone Imelda becoming more tightly wound in the Southern Indian Ocean. Credit: NASA Goddard MODIS Rapid Response Team
Tropical Cyclone Imelda is churning in the open waters of the Southern Indian Ocean and NASA's Aqua satellite captured a visible image of the storm that showed bands of thunderstorms were wrapping tightly into the center of circulation.

On Friday, April 5, Imelda was a low pressure area designated "93S" that appeared ripe for development on NASA satellite imagery. On Saturday, April 6, 93S consolidated and became a tropical depression. Now, that depression has strengthened into a tropical storm, and is expected to continue strengthening to hurricane-force.

When NASA's Tropical Rainfall Measuring Mission (TRMM) satellite passed over Imelda on April 8 at 0408 UTC (12:08 a.m. EDT) it revealed low-level bands of thunderstorms over the western semicircle, while northeast of the center, the bands of thunderstorms were fragmented and weak. Since then, those bands have organized.

NASA's Aqua satellite passed over the low pressure area on April 8 at 0605 UTC (2:05 a.m. EDT) and the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument captured a visible image of Tropical Cyclone Imelda in the Southern Indian Ocean. MODIS imagery showed a large band of thunderstorms wrapping into the center of circulation from the south. That band of thunderstorms has been slowly consolidating over the 12 hours previous.

On April 8 at 0900 UTC (5 a.m. EDT) Imelda had maximum sustained winds near 40 knots (46.0 mph/74.0 kph). Imelda was centered near 11.0 south latitude and 64.7 east longitude, about 490 nautical miles west-southwest of Diego Garcia and moving to the west at 12 knots (13.8 mph/22.2 kph). Diego Garcia is an atoll in the shape of a footprint that is made up of coral. It is located south of the equator in the central Indian Ocean, in British Indian Ocean Territory.

Forecasters at the Joint Typhoon Warning Center (JTWC) noted that the easterly vertical wind shear has relaxed slightly to 10 to 15 knots (11.5 to 17.2 mph/18.5 to 27.8 kph). JTWC forecasters expect Imelda to continue tracking west southwestward for the next two days and strengthen.

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



April 05, 2013

NASA's Aqua Satellite Sees Developing Tropical Depression in So. Indian Ocean

MODIS image of System 93S› Larger image
NASA's Aqua satellite passed over the low pressure area on April 5 at 0826 UTC (4:26 a.m. EDT) and the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument captured a visible image of the low. Credit: NASA/NRL
NASA satellite data has revealed that a low pressure area in the Southern Indian Ocean has been getting better organized, and appears ripe for development into a tropical depression.

On April 5 at 1300 UTC (9 a.m. EDT), System 93S was located near 11.3 south latitude and 74.7 east longitude, about 270 nautical miles (310.7 miles/500 km) south-southeast of Diego Garcia. NASA's Aqua satellite passed over the low pressure area on April 5 at 0826 UTC (4:26 a.m. EDT) and the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument captured a visible image of the low.

Satellite imagery showed that convective bands (thunderstorms) had strengthened and wrapped more tightly into the well-defined center of circulation. Sustained winds near 30 knots (34.5 mph/55.5 kph) are feeding into the center from the western and southern quadrants, according to the Joint Typhoon Warning Center.

System 93S is moving over ocean waters as warm as 29 degrees Celsius (84.2 Fahrenheit, which are warm enough to support further tropical cyclone development. The Joint Typhoon Warning Center estimates that System 93S' maximum sustained winds are between 28 and 33 knots (32.2 and 37.9 mph /51.8 and 61.1 kph).

It appears that System 93S may become Tropical Depression 19S over the weekend of April 6 and 7.

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