Featured Images

Text Size

Hurricane Season 2011: Tropical Storm 5A (Northern Indian Ocean)
12.01.11
 
TRMM's first image of Tropical Storm 05A was taken at 13:21 UTC (6:21 pm local time) November 29, 2011 › View larger image
TRMM's first image of Tropical Storm 05A was taken at 13:21 UTC (6:21 pm local time) November 29, 2011 and shows the horizontal pattern of rain intensity within the storm. The most prominent features are two long, thin rainbands containing mostly light (blue areas) to occasional areas of moderate (shown in green) rain that spiral in towards the center, revealing the presence of the storm's cyclonic circulation. The upper-level cloudiness (shown in white) is displaced well to the northwest of the low-level circulation and is a manifestation of the strong vertical wind shear affecting the storm.
Credit: NASA/SSAI, Hal Pierce
This TRMM image of Tropical Storm 05A was taken in the morning at 04:14 UTC (9:14 a.m. local time) on November 30. › View larger image
This TRMM image was taken the morning at 04:14 UTC (9:14 a.m. local time) on November 30. The upper-level clouds now extend back over the center, and there is an area of moderate rain (green area) in the northeast quadrant of the storm, but overall there is still very little rain associated with the system and still almost none near the center.
Credit: NASA/SSAI, Hal Pierce
Tropical Storm 05A was captured by the AIRS instrument on NASA's Aqua satellite on Dec. 1 at 08:47 UTC › View larger image
This infrared image of the remnants of Tropical Storm 05A was captured by the AIRS instrument on NASA's Aqua satellite on Dec. 1 at 08:47 UTC (3:47 a.m. EST). The blue areas represent the highest, coldest cloud tops. There is no circulation apparent on this image and no center as clouds and precipitation are now scattered.
Credit: NASA JPL, Ed Olsen
NASA's TRMM Satellite Catches Rainfall in Arabian Sea's Fading Tropical Cyclone

Tropical Storm 05A, the fifth of the season in the North Indian Ocean, has been steadily making its way northwestward across the Arabian Sea over the past few days but is now expected to weaken, reducing the threat to Oman, southern Iran and Pakistan. NASA's TRMM satellite captured images of rainfall and cloud heights while passing over the storm from its orbit in space. Tropical Storm 5A fell apart this morning and is being watched for regeneration.

The storm formed back on November 26th in the North Indian Ocean about 170 km (~105 miles) west of the southern tip of India and has maintained the same minimal tropical storm intensity with sustained winds of around 35 knots (~40 mph) while moving steadily to the northwest into the central Arabian Sea.

The Tropical Rainfall Measuring Mission satellite (known as TRMM) captured two images of the storm as it was moving through the Arabian Sea. TRMM was placed into service way back in November of 1997 and has proven to be a valuable platform for observing tropical cyclones in the Tropics using its combination of passive microwave and active radar sensors.

TRMM's first image of Tropical Storm 05A was taken at 13:21 UTC (6:21 p.m. local time) November 29, 2011 and shows the horizontal pattern of rain intensity within the storm. Rain rates in the center swath are from the TRMM Precipitation Radar (PR), and those 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). TRMM reveals that there is actually very little rain associated with the storm. The most prominent features are two long, thin rainbands containing mostly light to occasional areas of moderate rain that spiral in towards the center, revealing the presence of the storm's cyclonic circulation. The upper-level cloudiness is displaced well to the northwest of the low-level circulation and is a manifestation of the strong vertical wind shear affecting the storm.

The next image was taken the following morning at 04:14 UTC (9:14 a.m. local time) on November 30. The upper-level clouds now extend back over the center, and there is an area of moderate rain (green area) in the northeast quadrant of the storm, but overall there is still very little rain associated with the system and still almost none near the center.

On Dec. 1 at 08:47 UTC (3:47 a.m. EST an infrared image of the remnants of Tropical Storm 05A was captured by the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite. The highest, coldest cloud tops were widely scattered. There is no circulation apparent on the image, and clouds and precipitation are now scattered. The estimated location of the storm's center is near 19.2 North and 63.0 East, about 410 miles south-southwest of Karachi, Pakistan. The Joint Typhoon Warning Center gives this storm a low chance of regeneration.

In early November, Tropical Storm Keila made landfall in southern Oman, killing 14 people. Although the cyclone season is rather long in the North Indian Ocean, stretching from April through December, in an average year there are typically just over 5 named storms with only 2 becoming full tropical cyclones.

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

Text credit: Steve Lang
NASA TRMM Team/NASA's Goddard Space Flight Center, Greenbelt, Md.














Nov. 30, 2011

MODIS captured a visible image of Tropical Storm 5A on Nov. 30, 2011 at 06:40 UTC (1:40 a.m. EST) . › View larger image
NASA's Terra satellite flew over the Arabian Sea on Nov. 30, 2011 at 06:40 UTC (1:40 a.m. EST) and captured a visible image of Tropical Storm 5A. The image showed a large extent of clouds (about 200 miles) from 5A's northern quadrant.
Credit: NASA Goddard MODIS Rapid Response Team
This infrared image shows the coldest cloud top temperatures and strongest thunderstorms left in Storm 5A. › View larger image
This infrared image shows the coldest cloud top temperatures and strongest thunderstorms (in purple) remaining in Tropical Storm 5A on Nov. 29 at 21:11 UTC (4:11 p.m. EST). Cloud-top temperatures were colder than -63 Fahrenheit.
Credit: NASA JPL, Ed Olsen
NASA Satellite Sees Strong Wind Shear Taking Final Toll on Tropical Storm 5A

For the last two days, strong wind shear in the Arabian Sea has pushed most of the clouds and showers associated with Tropical Storm 5A away from its center. Today, Nov. 30, NASA satellite imagery shows wind shear continues to push those clouds to the north and west of 5A's center and is taking a big toll on the entire cyclone.

At 03:00 UTC on Nov. 30 (or 10 p.m. EST, Nov. 29), the Joint Typhoon Warning Center issued their final advisory on Tropical Storm 5A (5A). At that time, it was about 485 nautical miles (558 miles/898 km) south-southeast of Karachi, Pakistan near 17.5 North latitude and 63.8 East longitude. 5A's maximum sustained winds were still holding at 35 knots (40 mph/65 kmh) but wind shear was battering and weakening the storm. 5A was moving westward at 11 knots (13 mph/20 kmh) and is expected to turn to the southwest on Dec. 1.

Infrared imagery from NASA's Atmospheric Infrared Sounder (AIRS) instrument on the Aqua satellite showed a partially exposed low level center of circulation today, and the strongest convection and thunderstorms over the Tropical Storm 5A's western quadrant. The convection (rapidly rising air that forms those thunderstorms that make up the storm) is waning because it continues to be battered by southerly vertical wind shear between 20 and 30 knots (23 and 35 mph/ 37 and 55 kmh). There were also no bands of thunderstorms visible in the AIRS infrared image, another indication that the storm was weakening.

The Joint Typhoon Warning Center (JTWC) has forecast Tropical Storm 5A to turn to the southwest tomorrow, December 1 as a result of a shortwave trough (elongated area of low pressure) that will push it in that direction. The trough will steer Tropical Storm 05A away from the Oman coast. JTWC also expects 5A to dissipate late in the day tomorrow.

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








Nov. 29, 2011

On Nov. 29, 2011 MODIS captured a visible image of Tropical Storm 5A at 12:55 a.m. EST. › View larger image
NASA's Terra satellite flew over the Arabian Sea on Nov. 29, 2011 and captured a visible image of Tropical Storm 5A at 12:55 a.m. EST. The image showed a large extent of clouds (about 200 miles) from 5A's northern quadrant that stretched from the center of the storm to Gujarat, a state in western India.
Credit: NASA Goddard MODIS Rapid Response Team
NASA's Terra Satellite Sees Tropical Storm 5A's Long Reach

Tropical Storm 5A continues to spin in the Arabian Sea, and although a minimal tropical storm, its clouds and form appeared impressive on NASA satellite imagery, Tropical Storm 5A also appeared to have a "reach" of over 200 miles that enabled it to touch western India.

NASA's Terra satellite flew over the Arabian Sea on Nov. 29 and captured a visible image of Tropical Storm 5A at 5:55 UTC (8:55 a.m. local time, Somalia/12:55 a.m. EST). The image showed a large extent of clouds (about 200 miles) from 5A's northern quadrant that stretched from the center of the storm to Gujarat, a state in western India. The cloud cover extends that far and in that direction because of strong southerly wind shear. Despite the fact that 5A is just a tropical storm, satellite imagery revealed what appears to be an eye in the center of circulation. The center also appears well-defined through multispectral satellite imagery. Despite a well-formed center, it is now also fully exposed to outside winds, meaning that it has a chance to weaken more quickly from outside influences.

Tropical Storm 5A's maximum sustained winds were near 35 knots (40 mph/65 kmh) on Nov. 29 at 1500 UTC (10 a.m. EST). It was centered about 515 nautical miles (592 miles/954 km) south of Karachi, Pakistan, near 16.4 North and 65.9 East. 5A was moving to the north-northwest at 5 knots (6 mph/9 kmh).

Tropical Storm 5A is forecast to continue tracking northwestward across the Arabian Sea over the next two days. The Joint Typhoon Warning Center forecast calls for the wind shear to take its toll, however, and weaken 5A to a depression and perhaps a remnant low in that time.

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



Nov. 28, 2011

IR images of Tropical Storm 5A › View larger image
These two infrared images of Tropical Storm 5A from NASA's AIRS instrument (on the Aqua satellite) show the storm get better organized and more rounded between Nov. 26 and 27, 2011. The purple color indicates the strongest, coldest, highest cloud tops, where heavy rain is likely falling. The area of strong thunderstorms increased and became more organized on Nov. 27.
Credit: NASA JPL, Ed Olsen
Tropical Storm 5A More 'Well-Rounded' on NASA Infrared Imagery, for Now

Over the past several days Tropical Storm 05A has become better organized on infrared satellite imagery from NASA. Imagery from NASA's Aqua satellite over two days has shown that the cold cloud tops in the cyclone have become more rounded as the storm consolidates and strengthens.

NASA's Aqua satellite made two passes over Tropical Storm 05A (5A) and noticed the changes. The first pass happened on Nov. 26 at 08:23 UTC (3:23 a.m. EST and the infrared image from the Atmospheric Infrared Sounder (AIRS) instrument on Aqua revealed that 5A's clouds were not circular in nature, indicating a struggle within the storm to get organized. At that time, 5A was located near 9.3 North and 73.6 East, about 160 miles (257 km) west-southwest of Cochin, India.

By Nov. 27 at 21:23 UTC (4:23 p.m. EST) 5A had become circular in shape indicating that the storm did get better organized. At that time, maximum sustained winds were near 40 mph (35 knots/65 kmh) and it was 360 miles (579 km) south-southwest of Mumbai, India. That organization may be short-lived however, as wind shear increases and batters the circulation of the storm.

AIRS infrared imagery measures cloud top and sea surface temperatures, two factors that help determine the behavior of tropical cyclones. The colder the cloud tops are the higher the clouds and the stronger the thunderstorm (and heavier rain). The warmer the sea surface temperatures are, the higher the thunderstorm cloud tops are likely to rise and the stronger they are likely to become. Sea surface temperatures of at least 80F (26.6C) are needed to maintain a tropical cyclone, and they are currently near 84.2F (29C) in the Bay of Bengal where 5A lingers.

On Nov. 28 at 1500 UTC (10 a.m. EST), Tropical Storm 05A had maximum sustained winds still holding near 40 mph (35 knots/65 kmh). It was located 590 miles south of Karachi, Pakistan near 15.2 North and 67.8 East. 5A was moving to the northwest at 8 knots (9 mph/14 kmh) and generating seas of 17 feet (5.1 meters) high. Infrared imagery today shows that the banding of thunderstorms in the southeastern quadrant of the storm have thinned, a sign of weakening.

Forecasters say that it will track northwest across the Arabian Sea toward Somalia and strengthen a little more before running into wind shear that is expected to weaken the storm.

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



November 25, 2011

Aqua captured this infrared image of System 98B, developing into a tropical depression in the Northern Indian Ocean on Nov. 25, 2011. › View larger image
NASA's Aqua satellite captured this infrared image of System 98B, developing into a tropical depression in the Northern Indian Ocean on Nov. 25, 2011. The low pressure center is consolidating, and 98B is expected to become a tropical storm. Credit: NASA/NRL
NASA's Aqua Satellite Sees Tropical Depression 98B in North Indian Ocean

NASA's Aqua Satellite is watching a low pressure area in the northern Indian Ocean that has become a tropical depression. Tropical Depression 98B continues to consolidate and organize, and over the last 24 hours and bands of thunderstorms have formed around its center.

When bands of thunderstorms form around a developing low, it is an indication that the storm is strengthening and getting organized. The Moderate Resolution Imaging Spectroradiometer instrument on NASA's Aqua satellite captured an infrared image of System 98B that showed its cloud cover consolidating into a rounded area of clouds, indicating better circulation.

On Nov. 25, System 98B had maximum sustained winds between 25 and 30 knots (34 mph/55 kmh) which is tropical depression strength. It is located near 4.9 North latitude and 78.3 East longitude and is moving northwest at 13 knots (15 mph/24 kmh). That's about 150 miles (241 km) southwest of Colombo, Sri Lanka. It is forecast by the Joint Typhoon Warning center to continue moving to the northwest and may affect southwestern India over the next several days.

The Joint Typhoon Warning Center gives System 98B a high chance of becoming a tropical storm in the next 48 hours.

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