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Hurricane Season 2011: Tropical Cyclone Cherono (Southern Indian Ocean)
03.22.11
 
March 22, 2011

NASA's TRMM Satellite Sees Heavy Rainfall in Cherono's Fading Remnants

satellite image of Cherono TRMM captured an area of heavy rainfall still occurring in the remnants of Cyclone Cherono on March 22 at 0225 UTC. The yellow and green areas indicate moderate rainfall between .78 to 1.57 inches (20-40 mm) per hour. Red areas are considered heavy rainfall at almost 2 inches (50 mm) per hour. Credit: NASA/SSAI, Hal Pierce
› Larger image
NASA and the Japanese Space Agency's Tropical Rainfall Measuring Mission (TRMM) satellite flew over the center of the remnants of the once Cyclone Cherono and saw some heavy rain still existing in the storm as it dissipates.

The TRMM satellite passed directly above the remnants of tropical cyclone Cherono in the South Indian Ocean on March 22, 2011 at 0225 UTC (March 21 at 10:25 p.m. EDT). TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) showed that Cherono, although weakened, still had some life and was producing very heavy rainfall of over 50 mm/hr (~2 inches) south-southeast of Reunion Island.

The image of Cherono's rainfall was created by Hal Pierce of the TRMM team at NASA's Goddard Space Flight Center in Greenbelt, Md. Rain rates in the center of the image swath are from the TRMM PR, the only spaceborne radar of its kind, while those in the outer portion are from the TMI. The rain rates are overlaid on infrared (IR) data from the TRMM Visible Infrared Scanner (VIRS).

For more information about TRMM, visit: http://www.trmm.gsfc.nasa.gov/.

Text credit:Hal Pierce, SSAI/NASA's Goddard Space Flight Center, Greenbelt, Md.



March 21, 2011

AIRS image of Cherono› View larger image
These three days of AIRS infrared imagery show how wind shear took its toll on Cyclone Cherono and weakened it to a remnant low pressure area. On March 19 (left) it was a tropical storm with a band of thunderstorms around west of center. On March 20 the banding was gone and strong convection (purple) was limited to north of the center of circulation. By March 21 Cherono had become asymmetric from wind shear and weakened to a remnant low. Credit: NASA JPL, Ed Olsen
NASA Infrared Satellite Imagery Shows Cyclone Cherono Dwindling

Three days of NASA infrared satellite imagery provides a clear picture to forecasters of the effect wind shear has had on former Cyclone Cherono. Wind shear increased near Cyclone Cherono this weekend and weakened it down to a remnant low pressure area in the Southern Indian Ocean. Today, March 21, Cherono's remnants are moving away from Mauritius and still causing ocean swells.

NASA's Aqua satellite flew over former Tropical Cyclone Cherono each day over the last three days and the Atmospheric Infrared Sounder (AIRS) instrument captured the effects of the increased wind shear in infrared imagery.

AIRS infrared imagery on March 19 at 09:35 UTC showed a concentrated center of circulation with a band of thunderstorms stretching from southwest to northwest outside the center of Cherono's circulation. At that time Cherono was still a tropical storm. On March 20 at 21:11 UTC, AIRS imagery revealed that those bands of thunderstorms around Cherono had disappeared as a result of the increased wind shear. On Sunday, March 20, the strongest convection (rapidly rising air that forms the thunderstorms that power a tropical cyclone) was located to the north of the center of circulation.

By March 21 at 09:17 UTC, NASA AIRS infrared imagery showed that Cherono had become asymmetric from wind shear. When a tropical cyclone becomes asymmetric it weakens. Think of a tropical cyclone as a haystack: when the bottom of the haystack is blown outward (as with wind shear), the top of the haystack collapses. The same kind of thing happens with the layers of atmospheric circulation in the storm's center.

The Mauritius Meteorological Service warns that as the remnant low pressure area formerly known as Cyclone Cherono continues to move away today, March 21. As a result, rough surf and heavy ocean swells can be expected today and residents are being warned not to go in the ocean, especially beyond reef areas.

The last warning on Cherono from the Joint Typhoon Warning Center came on Saturday, March 19, when Cherono was still a Tropical Storm with maximum sustained winds near 40 mph (35 knots/ 64 kmh). at that time it was located about 595 miles east of La Reunion Island near 19.7 South and 65.0 East, and was moving west-southwest near 9 mph (8 knots/ 14 kmh).

Over this past weekend, vertical wind shear increased battering the structure of Cyclone Cherono and weakening the circulation. Now the remnant low continues to move away from Mauritius and is expected to dissipate over the next day or two.

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



March 18, 2011

This 3-D image from TRMM shows that Cyclone 18S has towering clouds or › View larger image
This 3-D image of Cyclone 18S (now Cherono) was created from NASA and JAXA's TRMM satellite data on March 17 at 0212 UTC. The image shows that Cyclone 18S has towering clouds or "hot towers" over 15 kilometers (9 miles) high! Those high, hot towers are an indication of a strong and strengthening storm.
Credit: NASA/SSAI, Hal Pierce
TRMM rainfall rates within Tropical Cyclone 18S on March 17 at 0212 UTC. › View larger image
TRMM rainfall rates within Tropical Cyclone 18S on March 17 at 0212 UTC. TRMM showed that much of the rainfall occurring within the tropical cyclone was moderate (yellow and green), falling at a rate between 20 and 40 mm (.78 and 1.57 inches) per hour. There were some areas within the storm, however, where heavy rain (red) was falling at a rate of 50 mm (2 inches) per hour.
Credit: NASA/SSAI, Hal Pierce
AIRS showed strong convection (purple) with cloud top temperatures as cold as -52C/-63F. › View larger image
NASA's Aqua satellite passed over Tropical Cyclone 18S (now Cherono) on March 17 at 20:35 UTC and the AIRS instrument onboard captured an infrared image of the storm. The AIRS data showed strong convection (purple) with cloud top temperatures as cold as -52C/-63F, confirming the hot tower clouds from the TRMM satellite.
Credit: NASA/JPL, Ed Olsen
A 3-D Look at Tropical Storm Cherono from NASA Shows Strengthening

NASA's Aqua and TRMM satellites have noticed that thunderstorms are higher and stronger and rainfall has increased as Tropical Depression 18S became Tropical Storm Cherono in the Southern Indian Ocean today. NASA satellite data was used to create a 3 dimensional image of Cherono that showed powerful towering thunderstorms near its center that indicated it was strengthening.

On March 17, 2011 at 0212 UTC the Tropical Rainfall Measuring Mission (TRMM) satellite passed over tropical cyclone 18S (later named Cherono) that had formed and was intensifying in the open waters of the South Indian Ocean. 18S was already well organized and TRMM's Precipitation Radar (PR) showed that powerful thunderstorm towering clouds were located near 18S' center of circulation. These towering clouds know as chimney clouds or hot towers release a lot of energy and can serve to strengthen a tropical cyclone.

The TRMM data was used to put together an image of the strengthening storm in 3-D by Hal Pierce of the NASA TRMM Team at NASA's Goddard Space Flight Center in Greenbelt, Md. The 3-D image revealed that then Tropical Cyclone 18S had towering clouds or "hot towers" over 15 kilometers (9 miles) high! Those high hot towers were an indication of a strong and strengthening storm, and the next day, March 18, Cyclone 18S strengthened into Tropical Storm Cherono. The data for the image was captured by the TRMM satellite as it passed above on March 17 at 0212 UTC.

TRMM also captured the rainfall within Tropical Cyclone 18S showed that much of the rainfall occurring within the tropical cyclone was moderate, falling at a rate between 20 and 40 mm (.78 and 1.57 inches) per hour. There were some areas within the storm, however, where heavy rain was falling at a rate of 50 mm (2 inches) per hour. At the time TRMM passed, 18S was expected to attain strong tropical storm intensity and it did early this morning, March 18.

TRMM images are pretty complicated to create. At Goddard, rain rates in the center of the swath (the satellite's orbit path over the storm) are created from the TRMM PR instrument. The TRMM PR is the only space borne radar of its kind. The rain rates in the outer portion of the storm are created from a different instrument on the satellite, called the TRMM Microwave Imager. The rain rates are then overlaid on infrared data from the TRMM Visible Infrared Scanner. For more information about TRMM, visit: http://www.trmm.gsfc.nasa.gov/.

NASA's Aqua satellite passed over Tropical Cyclone 18S (now Cherono) on March 17 at 20:35 UTC and the Atmospheric Infrared Sounder (AIRS) instrument onboard captured an infrared image of the storm. The AIRS data showed strong convection (rapidly rising air that forms the thunderstorms that make up a tropical cyclone) with cloud top temperatures as cold as -52C/-63F confirming the hot tower clouds seen in the TRMM satellite data. The infrared data from AIRS also showed that bands of thunderstorms were wrapping into the center of the storm and that Cherono had taken on more of a signature shape of a developed tropical storm.

On March 18 at 0900 UTC, Tropical Storm Cherono had maximum sustained winds near 45 knots (52 mph/ 83 kmh). Tropical storm-force winds (winds of 34 knots/39 mph/63 kmh and higher) extended out 80 miles (128 km) from the center. Cherono's center of circulation was about 515 miles (828 km) south-southeast of Diego Garcia, near 16.5 South latitude and 72.4 East longitude. It was moving to the west-southwest near 10 knots (11 mph/18 kmh) and generating 17-foot (5 meter) high seas.

By the end of the weekend, Cherono is expected to start moving past Port Louis and La Reunion Island. Its center and strongest winds are expected to remain at sea; however, those islands will likely receive some heavy rainfall, gusty winds and strong surf on the islands east and south sides.

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



March 17, 2011

NASA's Aqua satellite flew 18S and captured the cold, strong thunderstorms (purple) surrounding the center. › View larger image
On March 17 at 08:05 UTC (4:05 a.m. EST) NASA's Aqua satellite flew over the eastern half of Tropical Storm 18S and captured the cold, strong thunderstorms (purple) surrounding the center. Those areas represent very high, cold, thunderstorm cloud tops where temperatures are as cold as or colder than -63F/-52C.
Credit: NASA/JPL, Ed Olsen
NASA Sees System 98S Become Tropical Storm 18S in the Southern Indian Ocean

Yesterday, infrared data from NASA's Aqua satellite confirmed that the low pressure area in the Southern Indian Ocean known as System 98S had become a tropical depression and saw indications it would strengthen. Today it has become a tropical storm named 18S.

Infrared data from the Atmospheric Infrared Sounder (AIRS) instrument that flies aboard NASA's Aqua satellite saw strong convection when it passed over System 98S, indicating that the tropical depression was strengthening. AIRS data from today, March 17 at 08:05 UTC (4:05 a.m. EST) continues to show increasing strong convection (rapidly rising air that forms the thunderstorms that power a tropical cyclone) surrounding the storm's center. Those areas represent very high, cold, thunderstorm cloud tops where temperatures are as cold as or colder than -63F/-52C.

Satellite imagery also shows the convective banding of thunderstorms that are wrapping into the center of the tropical storm's circulation indicating organization and strengthening.

On March 17, 2011 at 0900 UTC (5 a.m. EST), Tropical Storm 18S (TS18S) was located near 14.9 South latitude and 75.7 East longitude, about 500 nautical miles south-southeast of Diego Garcia. TS18S has maximum sustained winds near 35 knots (40 mph/64 kmh) and is moving west near 14 knots (16 mph/25 kmh).

Currently Tropical Storm 18S is in an area of low vertical wind shear, but that's expected to change as trough (elongated area) of low pressure in the upper atmosphere is expected to increase winds and cause subsidence (the sinking of air that will prevent the growth of thunderstorms that power the tropical cyclone).

Tropical Storm 18S is forecast by the Joint Typhoon Warning Center to move in a west-southwesterly direction and is expected to bring rains, gusty winds and rough surf to La Reunion Island early next week.

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



March 16, 2011

AIRS captured the cold, strong thunderstorms surrounding the center of System 98S in the Southern Indian Ocean. › View larger image
On March 15 at 08:17 UTC NASA's Aqua satellite captured the cold, strong thunderstorms (purple) surrounding the center of the low pressure area called System 98S in the Southern Indian Ocean.
Credit: NASA/JPL, Ed Olsen
NASA Imagery Shows Strong Thunderstorms Continue in Developing System 98S

System 98S has been battered with wind shear over the last couple of days and is still holding together as a tropical depression. Infrared satellite imagery from NASA's Aqua satellite revealed an area of strong convection and thunderstorms around the low pressure area's center yesterday, indicating that the low is maintaining strength even in adverse conditions.

On March 16, System 98S was located about 615 nautical miles southeast of Diego Garcia, near 14.2 South latitude and 80.3 East longitude in the Southern Indian Ocean. The Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite has been capturing imagery of the low pressure area and today showed that the low level circulation center east of the main area of convection is partially exposed to outside winds.

AIRS infrared imagery also showed that convection had begun flaring or increasing on the western side of the circulation center during the morning hours, indicating strengthening. Flaring convection means the creation of more towering thunderstorms. Thunderstorms power a tropical cyclone. There was also an indication in microwave satellite imagery that thunderstorms were wrapping around the low level center.

Maximum sustained winds are now between 25 and 30 knots (29 to 34 mph/46 to 55 kmh) despite moderate vertical wind shear of 15 to 20 knots (17 to 23 mph/ 28 to 37 kmh). System 98S is in a region of warm water which is needed to continue feeding the low. The Joint Typhoon Warning Center said that System 98S has a fair chance of becoming a tropical storm in the next 24 hours.

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



March 14, 2011

AIRS revealed some strong convection around System 98S' center of circulation on March 14, 2011 at 07:35 UTC. › View larger image
The AIRS instrument that flies aboard NASA's Aqua satellite revealed some strong convection (purple) around the center of System 98S' center of circulation on March 14, 2011 at 07:35 UTC (3:35 a.m. EST). Although the low level circulation center was partially exposed to outside winds, convection has increased.
Credit: NASA/JPL, Ed Olsen
Infrared Satellite Imagery Shows Potential for Tropical Development of System 98S

A Low pressure area in the Southern Indian Ocean is showing signs of strengthening and organizing on infrared satellite imagery from NASA today.

The Atmospheric Infrared Sounder (AIRS) instrument that flies aboard NASA's Aqua satellite revealed some strong convection around the center of System 98S' center of circulation on March 14, 2011 at 07:35 UTC (3:35 a.m. EST). Although the low level circulation center was partially exposed to outside winds, convection has increased.

A large area of thunderstorms had cloud top temperatures that were as cold as or colder than -63 Fahrenheit/-52 Celsius, a threshold in AIRS data that indicates strong convection (rapidly rising air that forms thunderstorms that power a tropical cyclone.

At 1000 UTC (7 a.m. EST) on March 14, System 98S was located about 620 nautical miles west of the Cocos Islands near 11.4 South and 86.2 East. Vertical wind shear is low, between 15 and 20 knots and sea surface temperatures are warm enough to sustain and power a tropical cyclone, so the Joint Typhoon Warning Center gives System 98S a fair chance of developing into a tropical depression.

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