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Kate (Southern Indian Ocean)
December 31, 2014

[image-132]NASA Sees Tropical Cyclone Kate Meeting its End

NASA's Aqua satellite passed over Tropical Cyclone Kate on Dec. 31 and took an image of the storm that showed how wind shear had ripped it apart.

When NASA's Aqua satellite flew over Kate on Dec. 31 at 0800 UTC (3 a.m. EST), the MODIS instrument aboard took a visible picture of the storm. The MODIS image clearly showed that wind shear had pushed the thunderstorms that make up the tropical cyclone, south of the center leaving the northern and eastern quadrants of the storm almost devoid of clouds. Northeasterly wind shear had increased quickly and had taken the storm from a hurricane to a minimal tropical storm in 12 hours.

At 0300 UTC on Dec. 31 (10 p.m. EST on Dec. 30), Kate was hurricane strength with maximum sustained winds near 85 knots (97.8 mph/157.4 kph). Twelve hours later by 1500 UTC (10 a.m. EST), Kate's maximum sustained winds had dropped to just 35 knots (40 mph/62 kph). At that time Kate was centered near 20.9 south latitude and 85.5 east longitude, about 815 nautical miles (937 miles/1,509 km) southwest of Cocos Island, Australia. Kate was moving to the west-southwestward at 11 knots (12.6 mph/20.3 kph).

The Joint Typhoon Warning Center (JTWC) issued their final bulletin on Kate at 1500 UTC (10 a.m. EST). The JTWC forecast discussion noted "Animated multispectral satellite imagery shows the low level circulation center has unraveled and become fully exposed as the central convection has greatly eroded and sheared southwestward. Upper level analysis indicates the system has drifted into the mid-latitude westerlies into an area of strong vertical wind shear."

In addition to the increased wind shear, Kate moved into waters cooler than the 26.6 C/80F needed to maintain its strength.  Cooler waters and increased wind shear are expected to cause Kate to dissipate by January 1, 2015.

Rob Gutro
NASA's Goddard Space Flight Center


[image-114]Dec. 30, 2014 - NASA Sees Heaviest Rainfall North of Tropical Cyclone Kate's Eye

As Tropical Cyclone Kate continues moving southwest through the Southern Indian Ocean, NASA/JAXA's Tropical Rainfall Measuring Mission or TRMM satellite passed overhead on Dec. 30 and measured the rainfall rates happening throughout the storm.  Kate had strengthened since Dec. 29 and developed an eye.

The TRMM satellite flew over Kate on Dec.  30, 2015 at 0542 UTC (12:42 a.m. EST/U.S.). TRMM found that Kate was generating the heaviest rainfall rate of about 1.2 inches per hour north of the center as the storm strengthened.  TRMM data showed that rainfall rates around 1 inch per hour circled the center of the storm, with weaker rainfall rates in the southeastern quadrant of the storm.

At the Naval Research Laboratory, the TRMM rainfall rate data was overlaid on visible imagery from Europe's METEO-7 satellite to provide an entire picture of the storm that showed the rainfall and clouds. The METEO-7 satellite data showed that Kate maintained a circular shape and had a large band of thunderstorms wrapping into the center from the western quadrant.

At 1500 UTC (10 a.m. EST) on Dec. 30, Tropical Cyclone Kate's winds had increased to 105 knots (120.8 mph/194.5 kph). Kate's cloud-filled 5 nautical-mile-wide (5.7 mile/9.2 km) eye was centered near 8.2 south latitude and 89.1 east longitude, about 555 nautical miles (639 miles/1,029 km) south-southwest of Cocos Island, Australia. It was moving to the south-southwest at 10 knots (11.5 mph/18.5 kph).

The Joint Typhoon Warning Center (JTWC) noted that Kate will continue to track around the southwestern edge of a subtropical ridge (elongated area) of high pressure that is situated over Western Australia. JTWC forecasters expect Kate to begin weakening as it moves through cooler waters in the next couple of days, and dissipate within four days.

Rob Gutro
NASA's Goddard Space Flight Center


[image-69]Dec. 29, 2014 - NASA's Aqua Satellite Sees Tropical Cyclone Kate in Open Ocean

Tropical Cyclone Kate peaked in strength on Dec. 28, and NASA's Aqua satellite passed over the storm on Dec. 29 as it began weakening over the open waters of the Southern Indian Ocean.

On Dec. 28 at 2100 UTC (4 p.m. EST) Tropical Cyclone Kate had maximum sustained winds near 70 knots (80.5 mph/120.6 kph). It was centered near 14.6 south latitude and 92.1 east longitude, about 265 nautical miles (305 miles/491 km) west-southwest of Cocos Island.

The Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard Aqua captured a visible picture of Kate as it passed overhead on Dec. 29 at 8:15 UTC (3:15 a.m. EST). The MODIS image showed that bands of thunderstorms were spiraling into the center of the storm, despite having weakened slightly from the previous day.

On Dec. 29 at 9:00 UTC (4 a.m. EST) Tropical Cyclone Kate had maximum sustained winds near 65 knots (74.8 mph/120.4 kph) making Kate a minimal Category 1 hurricane on the Saffir-Simpson wind scale. It was centered near 14.9 south latitude and 91.7 east longitude, about 345 nautical miles (397 miles/638 km) west-southwest of Cocos Island. Kate continued moving away from Cocos Island- and in a southwesterly direction at 4 knots (4.6 mph/7.4 kph).

Satellite imagery also showed that the strongest convection (rising air that forms thunderstorms) continued around the storm's center and weak bands of thunderstorms are wrapping into the center. The Joint Typhoon Warning Center (JTWC) noted on Dec. 29 that it appeared that an eye feature was trying to form.

The JTWC discussion noted that "upper-level analysis indicates a decreasing environment as moderate to strong (20 to 30 knots) easterly vertical wind shear is offset by good outflow that is beginning to decrease. A tropical cyclone needs good outflow (where winds spread out at the top of the hurricane) to maintain strength. Outflow means that air spreads out over the top of the storm assisting in its development. When outflow is weakened, the storm weakens.

Kate is tracking slowly along the western part of a subtropical ridge of high pressure that is centered over Western Australia and will continue steering the storm in a southwestern direction.  The Joint Typhoon Warning Center calls for gradual weakening over the next two days as Kate moves into cooler waters which will cause the system's demise in a couple of days.

Rob Gutro
NASA's Goddard Space Flight Center


[image-77]Dec. 26, 2014 - NASA's Aqua Satellite Sees Tropical Cyclone Kate Passing Cocos Keeling Islands

Residents of the Cocos Keeling Islands in the Southern Indian Ocean had a Christmas day visitor they didn't want in the form of Tropical Cyclone Kate. Kate moved through the islands and triggered warnings on Dec. 25 before started moving away to the west. NASA's Aqua satellite caught a picture of Kate on Dec. 25 that showed the heaviest thunderstorms were west of the islands.

NASA's Aqua satellite passed over Kate on Dec. 25 at 0705 UTC (2:05 a.m. EST) and the Moderate Resolution Imaging Spectroradiometer or MODIS instrument captured a visible image of the storm. The MODIS image showed that the strongest thunderstorms (which appeared bright white on satellite imagery) were west of the islands although the islands were still being affected by the storm's northeastern quadrant at the time. Animated infrared satellite imagery shows the system has developed a cloud-filled eye as central convection has deepened.

On December 25 at 1500 UTC (10 a.m. EST) Kate had maximum sustained winds near 35 knots (40 mph/62 kph). Kate was centered near 12.4 south and 96.2 east, just 30 nautical (34.5 miles/55.5 km) miles southwest of Cocos Island, Australia. Kate was moving to the west at 8 knots (9.2 mph/14.8 kph). At that time, Kate was being battered by moderate wind shear from the northeast, and that wind shear was pushing the bulk of clouds and showers southwest of the low-level center.

By Dec. 26 after Kate had just passed the islands, it began to intensify, as maximum sustained winds increased to 70 knots (80.5 mph/129.6 kph). Forecasters at the Joint Typhoon Warning Center expect Kate to strengthen to 85 knots (97.8 mph/157.4 kph) on Dec. 27 before weakening again.

Kate was centered near 12.5 south latitude and 94.1 east longitude, or about 155 nautical miles (178.5 miles/287.3 km) west of Cocos Island. Kate was moving to the west at 3 knots (3.4 mph/5.5 kph).

Kate is forecast to move in a west-southwesterly direction over the next couple of days and weaken back to a depression as vertical wind shear increases.

Rob Gutro
NASA's Goddard Space Flight Center


[image-50]Dec. 24, 2014 - NASA-NOAA's Suomi NPP Satellite Spots Birth of Tropical Cyclone Kate 

The tropical low pressure area previously known as System 95S organized and strengthened into Tropical Cyclone Kate on Dec. 24 and the Cocos Keeling Islands are expected to feel its effects on Dec. 25 and 26. NASA-NOAA's Suomi-NPP satellite passed over Kate after it formed.

NASA-NOAA's Suomi NPP satellite flew over newborn Tropical Cyclone Kate on Dec. 24 at 06:39 UTC (1:39 a.m. EST) and the Visible Infrared Imaging Radiometer Suite or VIIRS instrument aboard captured a visible image of the storm. The VIIRS image showed strong thunderstorms around the center of circulation. There was also a large band of thunderstorms south of the center wrapping into it from the southwestern quadrant.

VIIRS is a scanning radiometer that collects visible and infrared imagery and "radiometric" measurements. Basically it means that VIIRS data is used to measure cloud and aerosol properties, ocean color, sea and land surface temperature, ice motion and temperature, fires, and Earth's albedo (reflected light).

According to the Australian Bureau of Meteorology (ABM), at 8:00 pm WST local time (7 a.m. EST) on Dec. 24, Tropical Cyclone Kate had maximum sustained winds near 65 kilometers per hour (40 mph). It is centered near 10.9 south latitude and 98.4 longitude, or about 225 km (139.8 miles) northeast of Cocos Island. Kate is moving to the west-southwest at 19 kph (11.8 mph).

ABM says "The system has intensified and has been name Tropical Cyclone Kate. It is possible that gales will commence on the [Cocos] islands before sunrise Thursday, Dec. 25 (Christmas Day). The period of greatest risk is likely to be during the afternoon and evening on Christmas Day.

ABM stated that cyclone impacts for the Cocos Keeling Islands should be expected during Christmas and Boxing Day. The Australian Federal Police have advised a Blue Alert for communities on Home and West Island. ABM noted that the center of the tropical cyclone is expected to pass close to the islands during the afternoon of Dec. 25 (local time) and will cause very rough seas as it approaches the Cocos Keeling Islands.

For updated forecasts, please visit the ABM website at:  http://www.bom.gov.au/cyclone,

Rob Gutro
NASA's Goddard Space Flight Center

Suomi NPP satellite flew over Tropical Cyclone Kate on Dec. 24
NASA-NOAA's Suomi NPP satellite flew over Tropical Cyclone Kate on Dec. 24 at 6:39 UTC (1:39 a.m. EST) after it formed in the Southern Indian Ocean.
Image Credit: 
NASA/NOAA
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hurricane with long tail over ocean, true color picture
NASA's Aqua satellite passed over Kate on Dec. 25 at 0705 UTC (2:05 a.m. EST) as it was moving through the Cocos Keeling Islands in the Southern Indian Ocean.
Image Credit: 
NASA Goddard MODIS Rapid Response
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Aqua image of Kate on Dec. 29
NASA's Aqua satellite captured this image of Kate on Dec. 29 at 8:15 UTC and showed bands of thunderstorms were spiraling into the center of the storm, despite having weakened slightly from the previous day.
Image Credit: 
NASA/NRL
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TRMM image of Kate
The TRMM satellite flew over Kate on Dec. 30, 2015 at 0542 UTC. Kate was generating heavy rain (1.2 inches per hour) north of the center (in red). TRMM data was overlaid on cloud images from Europe's METEO-7 satellite.
Image Credit: 
NASA/JAXA/NRL
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Terra image of Kate
NASA's Terra satellite captured this image of Tropical Cyclone Kate in the southern Indian Ocean on Dec. 30 at 04:35 UTC when it was hurricane force.
Image Credit: 
NASA Goddard MODIS Rapid Response
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Page Last Updated: December 31st, 2014
Page Editor: Lynn Jenner