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Hurricane Season 2012: Tropical Depression Ethel (Southern Indian Ocean)
01.23.12
 
NASA's Aqua satellite captured an infrared image of Tropical Storm Ethel (left) on January 21, 2012 at 09:05 UTC (4:05 a.m. EST) that showed an area of strong convection and strong thunderstorms (purple) around the center of Tropical Storm Ethel, moving in the open waters of the Southern Indian Ocea › View larger image
NASA's Aqua satellite captured an infrared image of Tropical Storm Ethel (left) on January 21, 2012 at 09:05 UTC (4:05 a.m. EST) that showed an area of strong convection and strong thunderstorms (purple) around the center of Tropical Storm Ethel, moving in the open waters of the Southern Indian Ocean.
Credit: NASA JPL, Ed Olsen
NASA Infrared Image Sees Ethel Going Extratropical

Infrared imagery from NASA's Aqua satellite revealed an area of strong convection and strong thunderstorms around the center of Tropical Storm Ethel, even as the storm continues to weaken and become extratropical.

The Joint Typhoon Warning Center (JTWC) issued its final advisory on Tropical Storm Ethel, at 1500 UTC (10 a.m. EST), Sunday, January 22, 2012. At that time, Ethel's maximum sustained winds were near 45 knots (52 mph/83 kph) and weakening as Ethel continues moving through the Southern Indian Ocean.

Ethel was about 635 nautical miles southeast of Port Louis, near 28.8 South and 65.9 East. It was moving to the south-southeastward at 20 knots (23 mph/37 kph).

The Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite captured an image of Tropical Storm Ethel on January 21, 2012 at 09:05 UTC (4:05 a.m. EST) that showed an area of strong convection and strong thunderstorms around the storm's center.

Satellite imagery revealed that wind shear uncoupled the storm's rainfall from the low level circulation center. Ethel was also becoming extratropical. The JTWC forecast for Ethel called for the storm to accelerate and weaken over the next day.

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



Jan. 20, 2012

When NASA's Aqua satellite passed over Ethel on January 19 at 4:17 a.m. EST the AIRS instrument measured the temperatures of Ethel's cloud tops. › View larger image
When NASA's Aqua satellite passed over Ethel on January 19 at 4:17 a.m. EST the AIRS instrument measured the temperatures of Ethel's cloud tops. Thunderstorm cloud tops around the entire center of circulation were colder than -63 Fahrenheit, as well as in some of the bands of thunderstorms that circled the center to the east and north.
Credit: NASA JPL, Ed Olsen
NASA Reveals Cyclone Ethel's Power in Frigid Cloud Tops

NASA's Aqua satellite saw icy cold cloud top temperatures in Tropical Storm Ethel on January 19, which hinted at intensification. On January 20, Ethel had indeed strengthened into cyclone with hurricane-force winds.

Infrared satellite imagery gives forecasters a clue to how high the cloud tops are that belong to thunderstorms that make up a tropical cyclone. The rule is - the higher the cloud top, the stronger the uplift and the stronger the thunderstorm.

When NASA's Aqua satellite passed over Ethel on January 19 at 09:17 UTC (4:17 a.m. EST) the Atmospheric Infrared Sounder (AIRS) instrument measured the temperatures of Ethel's cloud tops. Thunderstorm cloud tops around the entire center of circulation and in some of the bands of thunderstorms that circled the center to the east and north, were colder than -63 Fahrenheit (-52 Celsius). Those cold temperatures represent strong uplift and power within Ethel that hinted that it would intensify into a cyclone today, January 20. Today's infrared satellite data showed a symmetrical tropical cyclone with very strong convection (rising air that forms the thunderstorms that make up the cyclone) and strong thunderstorms around the center of circulation. A comparison of infrared satellite imagery from Jan. 19 and 20 showed that the area of strong thunderstorms has expanded, hinting that the hurricane-force winds are expanding in coverage from the center.

On January 20, 2012 at 1500 UTC (10 a.m. EST) the Joint Typhoon Warning Center (the organization that forecasts tropical cyclones in the Southern Indian Ocean) noted that Ethel had maximum sustained winds near 65 knots (75 mph/120 kmh) and was the strength of a Category one hurricane on the Saffir-Simpson Scale. Ethel was located about 410 nautical miles (471 miles/759 km) east of Port Louis near 19.7 South latitude and 64.5 East longitude. Port Louis is the largest city and the capital of Mauritius, which borders the Indian Ocean. Ethel was moving south at 10 knots (12 mph/~18 kmh) and away from Mauritius.

Although Maritius is not in the forecast path of Cyclone Ethel, the island of Rodrigues is under the gun. A Class III tropical cyclone warning is still in effect for Rodrigues today, January 20, 2012. Tropical storm winds, moderate to heavy rainfall and heavy surf are forecast for the island. Once past Rodrigues, Cyclone Ethel will continue moving southward toward cooler waters which will sap her strength over the weekend.

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



Jan. 19, 2012

NASA's Aqua satellite passed over Tropical Storm Ethel in the Southern Indian Ocean on January 19, 2012 at 09:30 UTC (4:30 a.m. EST). › View larger image
NASA's Aqua satellite passed over Tropical Storm Ethel in the Southern Indian Ocean on January 19, 2012 at 09:30 UTC (4:30 a.m. EST). The MODIS instrument aboard Aqua captured a visible image of the storm, and showed that it had good circulation with an identifiable center of circulation.
Credit: NASA Goddard MODIS Rapid Response Team
NASA Satellite Sees Birth of Tropical Storm Ethel, Now Threatening Rodrigues

NASA's Aqua satellite passed over Tropical Storm Ethel on January 19, 2012 after she was born in the Southern Indian Ocean. The island of Rodrigues is now under Tropical Cyclone Warnings as Ethel approaches and strengthens.

When Aqua passed over newborn Ethel at 09:30 UTC (4:30 a.m. EST) on Jan. 19, the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard Aqua captured a visible image of the storm, and showed that it had good circulation. The strongest storms appear to be around the center and northwest of center. Bands of thunderstorms from the east-southeast appear to spiral into Ethel's center on the MODIS satellite imagery.

At 0300 UTC on January 19 (10 p.m. EST, Jan. 18) Tropical Storm Ethel had maximum sustained winds near 35 knots (40 mph/65 kmh). Ethel was 810 miles east-northeast of La Reunion Island, centered near 14.2 South longitude and 67.7 East latitude. Ethel was moving to the west-southwest at 11 knots (~13 mph/20 kmh).

Currently, Ethel threatens the island of Rodrigues. Rodrigues is the smallest of the Mascarene Islands and was home to 40,000 people in 2006. It is a dependency of Mauritius. According to Wikipedia, it is located 348 miles (560 km) east of Mauritius island. It is surrounded by a coral reef and is about 43 square miles (109 kmĀ²).

The Mauritus Meteorological Service (MMS) has posted a tropical cyclone class two warning for Rodrigues. A class two warning means that within 12 hours, the warning area will likely experience hurricane-force wind gusts of 75 mph (120 kilometers) per hour. The MMS calls for downpours and gusty winds today, with rain becoming heavier and more frequent on January 20. Sustained winds are expected to be near 25 mph (40 kmh) with gusts as high as 56 mph (90 kmh) during the evening hours on Jan. 19, 2012. Seas are expected to be rough. For updates in French and Creole, visit: http://metservice.intnet.mu/?page_id=625.

Because Ethel is in an area with warm sea surface temperatures (warmer than the 80F/26.6C threshold needed to maintain a tropical cyclone) and low wind shear, she is expected to strengthen quickly into hurricane (cyclone) strength. Afterward, Ethel is expected to encounter increased wind shear conditions which will again weaken the storm.

The cyclone is forecast to intensify rapidly to hurricane strength before adverse atmospheric conditions prompt a weakening trend.

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