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Hurricane Season 2012: Tropical Storm Koji (Southern Indian Ocean)
03.12.12
 
MODIS captured this true-color, visible image of Tropical Cyclone Koji on March 10, 2012 at 08:15 UTC. › View larger image
The MODIS instrument onboard NASA's Aqua satellite captured this true-color, visible image of Tropical Cyclone Koji on March 10, 2012 at 08:15 UTC moving through the southern Indian Ocean.
Credit: NASA Goddard MODIS Rapid Response Team
NASA Sees Cyclone Koji Fading at Sea

Cyclone Koji is fading at sea on Monday, March 12, 2012, and NASA satellites have watched the system weaken over the last several days. On March 10, 2012 at 08:15 UTC the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument onboard NASA's Aqua satellite captured a true-color, visible image of Tropical Cyclone Koji moving through the southern Indian Ocean. The satellite imagery shows that Koji was starting to stretch, and that's a result of increasing wind shear. That wind shear picked up on March 11 and 12.

On March 12, 2012 at 0900 UTC (5 a.m. EDT), the final warning was issued on Cyclone Koji. At that time its maximum sustained winds were down to 35 knots (40 mph/~65 kph). It was located about 1,310 nautical miles south-southeast of Diego Garcia, near 27.9 South and 82.1 East. It was moving to the southeast at 13 knots (~15 mph/24 kph).

On March 12, satellite imagery showed that the center was fully exposed and the storm continued to elongate more. The storm was also missing any strong thunderstorms around its center, likely as a result of the cooler waters it is now tracking through.

The forecasters at the Joint Typhoon Warning Center noted that strong wind shear and cool sea surface temperatures are responsible for Koji's fade out. Koji is located under upper-level northwesterly flow with strong 30-40 knots (34.5-46.0 mph /55.5 - 74.0 kph) vertical wind shear and is tracking over cool sea surface temperatures that are around 23 degrees Celsius (73.4 F). A tropical cyclone needs sea surface temperatures near 26.6C (80F) to maintain strength. Anything colder than that will weaken the storm.

Koji is weakening rapidly and is forecast to dissipate later on March 12 as a result of the strong wind shear and cool waters.

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



Mar. 9, 2012

TRMM revealed powerful storm towers around KOJI's center were reaching heights of almost 15km (~9.3 miles). › View larger image
TRMM data from the flight over tropical storm Koji are shown in the 3-D image above. Those data reveal that an eye hadn't formed but powerful storm towers around KOJI's center were reaching heights of almost 15km (~9.3 miles).
Credit: NASA/SSAI, Hal Pierce
This image from NASA's TRMM satellite shows rainfall in the Tropical Storm Koji on March 8 › View larger image
This image from NASA's TRMM satellite shows rainfall in the Tropical Storm Koji on March 8. Strong storms were dropping rainfall at a rate of over 50mm per hr / ~2 inches (red). Light to moderate rainfall is depicted in blue and green was falling at a rate between .78 to 1.57 inches (20 to 40 mm) per hour.
Credit: NASA/SSAI, Hal Pierce
NASA's TRMM Satellite Sees Hot Towers in Cyclone Koji

Hot towers, or towering thunderclouds that give off an excessive amount of latent heat, usually indicate a tropical cyclone will strengthen in six hours, and NASA's TRMM satellite saw some of them as it passed by Tropical Storm Koji.

The Tropical Rainfall Measuring Mission (TRMM) satellite passed directly above an intensifying tropical storm in the South Indian Ocean called Koji on March 8, 2012 at 2053 UTC (3:53 p.m. EST). A rainfall analysis was made from TRMM Microwave Imager (TMI) and Precipitation Radar (PR) data. Those TRMM data reveal that Koji was getting organized with bands of heavy rainfall spiraling into the storm's center.

One of its most important features of TRMM's Precipitation Radar (PR) instrument is its ability to provide three dimensional profiles of precipitation from the surface up to a height of about 20km (12 mile). PR data from the flight over tropical storm Koji are shown in the 3-D image above. Those data reveal that an eye hadn't formed but powerful storm towers around KOJI's center were reaching heights of almost 15 km (~9.3 miles).

On March 8, 2012 at 0900 UTC (4 a.m. EST), Tropical Storm Koji had maximum sustained winds near 55 knots (63.2 mph/102 kph). It was located near 17.1 South and 86.1 East, about 1000 miles southeast of Diego Garcia and moving to the west at 12 knots (13.8 mph/22.2 kph).

Koji has been predicted to increase in intensity and reach hurricane force with peak winds of 70kts (~80 mph) on March 8, 2012. Koji is predicted to remain at hurricane force for only one day and then weaken while traveling southwestward of the open waters of the South Indian Ocean.

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









Mar. 8, 2012

MODIS captured Tropical Storm Koji on March 8, 2012 at 1616 UTC as it moved through the Southern Indian Ocean. › View larger image
NASA's MODIS instrument captured an infrared image of Tropical Storm Koji on March 8, 2012 at 1616 UTC as it moved through the open waters of the Southern Indian Ocean. Koji appears as a rounded area of clouds as the storm continued to consolidate and strengthen.
Credit: NRL/NASA
Tropical Cyclone 16S Becomes Tropical Storm Koji in the Southern Indian Ocean

Tropical Cyclone 16S was named Koji today as NASA satellites saw it moving through the open waters of the Southern Indian Ocean.

On March 8 at 900 UTC (4 a.m. EST) Tropical Storm Koji had maximum sustained winds near 45 knots (~52 mph/83.3 kph). It was located about 440 nautical miles west-southwest of Australia's Cocos Island and is centered near 15.9 South latitude and 90.0 East longitude. Koji is moving west-southwest at 16 knots (18.4 mph/29.6 kph) and will remain over open ocean.

Later in the day, NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) instrument captured an infrared image of Tropical Storm Koji on March 8, 2012 at 1616 UTC (11:16 a.m. EST) as it moved through the open waters of the Southern Indian Ocean. Koji appeared in infrared imagery as a rounded area of clouds, and there in no visible eye to the storm.

Satellite data did show that convection was strengthening. Thunderstorms were becoming stronger and wrapped more tightly around the center of circulation. Koji is expected to continue organizing and strengthening over the next couple of days before it runs into increasing wind shear and cooler sea surface temperatures that will sap its strength.

Koji is just north of a ridge of high pressure and is moving along the northern edge of it in a west-southwestern direction.

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



Mar. 7, 2012

Aqua passed over newborn Tropical Storm 16S on March 7 at 741 UTC (2:41 a.m. EST) › View larger image
When NASA's Aqua satellite passed over newborn Tropical Storm 16S on March 7 at 741 UTC (2:41 a.m. EST) it captured an infrared image of the storm's cloud top temperatures using the Atmospheric Infrared Sounder (AIRS) instrument. AIRS data showed that the coldest (purple) cloud top temperatures (colder than -63F/-52.7C) that included the bulk of the showers and strongest thunderstorms were around the storm's center, and in a band of thunderstorms wrapping into the center from the north.
Credit: NASA/JPL, Ed Olsen
NASA Sees Tropical Storm 16S Form in Southern Indian

The sixteenth tropical cyclone has formed in the southern Indian Ocean and NASA's Aqua satellite captured an image showing its center of circulation is organizing quickly.

When NASA's Aqua satellite passed over newborn Tropical Storm 16S on March 7 at 741 UTC (2:41 a.m. EST) it captured an infrared image of the storm's cloud top temperatures using the Atmospheric Infrared Sounder (AIRS) instrument. AIRS showed that the center was quickly organizing and consolidating and the storm appeared rounded on AIRS imagery.

AIRS data showed that the coldest cloud top temperatures (colder than -63F/-52.7C) and heaviest showers and strongest thunderstorms were around the storm's center, as well as in a band of thunderstorms that were wrapping into the center from the north.

Tropical Storm 16S had maximum sustained winds near 40 knots (46 mph/74 kph) on March 7, 2012. The strongest winds appeared to be in the southwestern quadrant of the storm. It was located about 155 nautical miles (178.4 miles/287.1 km) south-southwest of the Cocos Islands, Australia, and was moving southwestward at 10 knots (11.5 mph/18.5 kph).

Tropical Storm 16S is expected to move to the west-southwest through the southern Indian Ocean and not affect any land areas over the next several days.

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