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Hellen (Southern Indian Ocean)
April 2, 2014

[image-97][image-124]NASA Sees Tropical Cyclone's Hellen's Lively Remnants

Powerful Tropical Cyclone Hellen rapidly weakened after hitting northwestern Madagascar but Hellen's remnants have recently started to show signs of life. The TRMM satellite flew over these remnants in the Mozambique Channel on April 2, 2014 at 0143 UTC.

A rainfall analysis using the Tropical Rainfall Measuring Mission's (TRMM) Microwave Imager (TMI) and Precipitation Radar (PR) instruments found that some strong convective thunderstorms had developed in the area. It was revealed by TRMM PR data that rain was falling at a rate of over 75 mm/~ 3 inches in a few locations.

TRMM's Precipitation Radar (PR) data were used to create a 3-D image that showed the structure in the convective thunderstorms near the center of Hellen's remnants. The 3-D view showed that a few of these tall thunderstorms were reaching heights of over 16 km/9.9 miles.

At 1800 UTC/2:00 p.m. EDT on April 1, the center of Hellen's remnants were located near 18.3 south and 42.3 east, about 271 nautical miles/311.9 miles/501.9 km west of  Antananarivo, Madagascar. Maximum sustained winds were estimated as high as 25 knots/28.7 mph/46.3 kph, and minimum sea level pressure was near 1004 millibars. The low-level circulation center appeared slightly elongated and the convection and thunderstorm development is disorganized.

The Joint Typhoon Warning Center expects the remnant low to move on a westward track toward Mozambique over the next couple of days. The system has a low chance of regenerating in the next 24 hours.

Text credit: Hal Pierce/Rob Gutro
SSAI/NASA's Goddard Space Flight Center

 

 

 


[image-78] [image-94]Apr. 01, 2014 - NASA Caught Tropical Cyclone Hellen's Rainfall Near Peak

When Tropical Cyclone Hellen was near the "peak of her career" NASA's TRMM satellite picked up on her popularity in terms of tropical rainfall. Hellen was a very heavy rainmaker in her heyday with heavy rain rates. Hellen weakened to a remnant low pressure area by April 1, but has now re-emerged in the Mozambique Channel.

Tropical Cyclone Hellen formed in the Mozambique Channel northwest of Madagascar on March 28, 2014. Hellen became a very powerful tropical cyclone with peak sustained winds of 130 knots/about 150 mph/241 kph on March 30, 2014. Hellen's eye came ashore in northwestern Madagascar on March 31 with winds predicted to be about 95 knots/109 mph/176 kph. 

NASA and the Japan Aerospace Exploration Agency's Tropical Rainfall Measuring Mission satellite known as TRMM passed above Hellen on March 30, 2014 at 17:47 UTC/1:47 p.m. EDT when the tropical cyclone was close to peak power.

A TRMM rainfall analysis that was derived from TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) data collected found that rain was falling at a rate of over 44 mm/1.7 inches per hour near the eye. Bands of moderate to heavy rain were shown moving over the northwestern coast of Madagascar.

TRMM PR data were collected at the same time in a swath that passed near the northern edge of tropical cyclone Hellen's eye wall. Those data were used to create a simulated 3-D view of Hellen's precipitation and also revealed that some powerful storms in Hellen's eye wall were reaching heights of over 13 km/8 miles.

Hellen seemed to run out of steam over Madagascar and the Joint Typhoon Warning Center issued the final warning on the tropical low pressure area on April 1 at 0300 UTC/March 31 at 11 p.m. EDT. AT that time, Hellen was centered near 17.0 south latitude and 46.1 east longitude, about 130 nautical miles/~150 miles/~241 km north-northwest of Antananarivo, Madagascar. Hellen was trudging to the south-southeast at 5 knots/5.7 mph/9.2 kph as it continued weakening. 

Thirty minutes after the last warning from the JTWC, Hellen's remnants had moved back over water in the Mozambique Channel. The JTWC noted that because of favorable conditions such as warm water and low wind shear, the storm could regenerate in the next couple of days.

Text credit:  Harold F. Pierce / Rob Gutro
SSAI/NASA Goddard Space Flight Center


[image-51]Mar. 31, 2014 - Tropical Cyclone Hellen Makes Landfall in Madagascar

Tropical Cyclone Hellen made landfall in west central Madagascar as NASA's Aqua satellite passed overhead capturing temperature data on its towering thunderstorms.

When NASA's Aqua satellite passed over Madagascar on March 31 at 10:47 UTC/6:47 a.m. EDT and the Atmospheric Infrared Sounder or AIRS instrument aboard captured infrared data on Hellen. AIRS data showed powerful thunderstorms circling the center of circulation with cloud top temperatures in excess of -63F/-52C indicating they were high into the troposphere. Thunderstorms reaching those heights also have the potential for heavy rainfall

Hellen developed during the week of March 23 in the Mozambique Channel, the body of water that lies between the island nation of Madagascar and Mozambique on the African mainland. By March 26, at 20:00 UTC/4 p.m. EDT, the tropical low, then known as System 95S was centered near 10.7 south latitude and 39.4 east longitude. The low level center was actually over land just inland from the coast, and sitting over the Tanzania and Mozambique border.

It was on March 26, that the Joint Typhoon Warning Center or JTWC noted that the low had a high chance for becoming a tropical depression in the next 24 hours.  JTWC noted that enhanced infrared satellite imagery on March 26 revealed that the low-level circulation center has consolidated and there were bands of thunderstorms wrapping into it. JTWC estimated that maximum sustained winds are between 25 to 30 knots/ 28.7 to 34.5 mph/46.3 to 55.5 kph.

At that time, the tropical low was in an area that had low vertical wind shear and warm sea surface temperatures that forecasters at JTWC said would provide the fuel for thunderstorms to develop and assist the low's growth. Over the next several days, System 95S moved east and back into the Mozambique Channel where it rapidly intensified into Tropical Cyclone Hellen and reached Category IV status on the Saffir-Simpson Scale when maximum sustained winds peaked near 140 knots/161.1 mph/259.3 kph.

By March 31 at 1500 UTC/11 a.m. EDT, Hellen's maximum sustained winds dropped to 85 knots/97.8 mph/ 157.4 kph because of the interaction with Madagascar. It was centered near 16.2 south latitude and 45.9 east longitude, about 180 nautical miles/207.1 miles/333.4 km north-northwest of Antananarivo, Madagascar.

The NOAA-19 satellite showed that the bulk of strongest thunderstorms were south of the center as a result of wind shear. In addition there is dry air moving into the center of circulation which is also helping to weaken Hellen. 

Hellen was moving slowly to the south-southeast at 5 knots/5.7 mph/9.2 kph, and the JWTC expects it to curve to the southwest and re-enter the Mozambique Channel.

Text credit:  Rob Gutro
NASA's Goddard Space Flight Center

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AIRS image of Hellen
When NASA's Aqua satellite passed over Madagascar on March 31 at 10:47 UTC/6:47 a.m. EDT it showed powerful thunderstorms circling the center of Hellen (purple).
Image Credit: 
NASA/JPL, Ed Olsen
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On March 30, the TRMM satellite showed some powerful storms in Hellen's eye wall were reaching heights of over 13 km/8 miles.
On March 30, the TRMM satellite showed some powerful storms in Hellen's eye wall were reaching heights of over 13 km/8 miles.
Image Credit: 
SSAI/NASA, Hal Pierce
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This 3-D simulated flyby of Tropical Cyclone Hellen on March 30, showed some powerful storms in Hellen's eye wall were reaching heights of over 13 km/8 miles.
Image Credit: 
SSAI/NASA, Hal Pierce
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Remnants of Hellen
The TRMM satellite flew over Hellen's remnants in the Mozambique Channel on April 2, 2014 at 0143 UTC and saw some thunderstorms topped out near 9.9 miles high.
Image Credit: 
SSAI/NASA, Hal Pierce
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This is a simulated 3-D flyby animation using TRMM PR data that shows some of the thunderstorms in Tropical Cyclone Hellen's remnants were near 9.9 miles high.
Image Credit: 
SSAI/NASA, Hal Pierce
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Page Last Updated: April 2nd, 2014
Page Editor: Lynn Jenner