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Tropical Cyclone Sandra (Southern Pacific Ocean)
03.14.13
 
MODIS image of Sandra› Larger image
This infrared image of an elongated Cyclone Sandra was captured on March 14 at 1146 UTC (7:46 a.m. EDT) by the MODIS instrument aboard NASA's Terra satellite. Credit: NASA/NRL
NASA Satellite Reveals Cyclone Sandra Stretching Out

Cyclone Sandra is fading in the South Pacific Ocean and a recent image from NASA's Terra satellite shows that wind shear has stretched the storm from east to west.

When a storm elongates and is no longer circular it weakens, and Cyclone Sandra has stretched out as a result of moving into an area of stronger wind shear.

The MODIS instrument aboard NASA's Terra satellite captured an infrared image of Cyclone Sandra on March 14 at 1146 UTC (7:46 a.m. EDT) the showed the remaining thunderstorms in the system were over the "right front quadrant" according to the Joint Typhoon Warning Center. Satellite imagery also showed that stratocumulus cloud fiends were streaming in from the east. Stratocumulus clouds indicate that there is stable air moving into the low pressure area, which would prevent rising air and the formation of thunderstorms (which make up a tropical cyclone).

On March 13 at 0300 UTC, the Joint Typhoon Warning Center issued their final bulletin on Sandra. At that time, Sandra's maximum sustained winds were near 40 knots (46 mph/74 kph) and weakening. Sandra was located about 465 nautical miles south-southwest of Noumea, New Caledonia, near 29.1 south and 162.1 east. Sandra continues to weaken as it moves south at 20 knots (23.0 mph/37.4 kph) and is expected to dissipate in another day.

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



March 13, 2013

TRMM image of Sandra› Larger image
TRMM's Microwave Imager (TMI) data showed Sandra's rainfall on March 11, 2013 at 2124 UTC. Moderate rainfall appears in green. Sandra's previous and forecast locations are shown overlaid in white on this rainfall analysis. NASA/SSAI, Hal Pierce

TRMM image of Sandra› Larger image
TRMM's Precipitation Radar (PR) had a very good view of Sandra as it passed directly above the tropical cyclone on March 11, 2013 at 1312 UTC. Heavy rainfall (red and pink) was falling south of the center. Credit: NASA/SSAI, Hal Pierce
NASA Sees Large Decrease in Cyclone Sandra's Rainfall Intensity

NASA's Tropical Rainfall Measuring Mission satellite, also known as TRMM, flew over Cyclone Sandra twice in one day and noticed a large decrease in rainfall intensity over a nine hour period.

On March 11, 2013, NASA's TRMM satellite twice flew above weakening tropical cyclone Sandra as it was passing to the west of New Caledonia in the southern Pacific Ocean. TRMM's Precipitation Radar (PR) had a very good view of Sandra as it passed directly above the tropical cyclone on March 11 at 1312 UTC (9:12 a.m. EST). TRMM PR measured rainfall at the extreme rate of over 206 mm (~8 inches) per hour in an area southwest of Sandra's eye. Those TRMM PR data also showed that very little rain was occurring north of the weakening tropical cyclone's eye.

New Caledonia escaped the heaviest precipitation as the center of Sandra remained off-shore.

Later on that day at 2124 UTC (4:24 p.m. EDT), TRMM's Microwave Imager (TMI) data identified diminished rainfall rates. The heaviest rains occurring south of Sandra's center at that time was falling at a rate of 30 mm (1.18 in) per hour. Wind shear continues to increase from the north and push the precipitation south of Sandra's center. Sandra's center has since become fully exposed to outside winds as the intensity of rainfall has diminished.

On Mar. 13 at 0300 UTC, Sandra's maximum sustained winds were near 55 knots (63.2 mph/101.9 kph). Sandra was located near 24.1 south and 161.5 east, about 270 nautical miles (310.7 miles/500 km ) west-southwest of Noumea, New Caledonia. Sandra was moving to the south-southwest at 8 knots (9.2 mph/14.8 kph).

Sandra is moving into an area of high vertical wind shear and colder sea surface temperatures that are expected to make the storm transform into a cold-core system before it dissipates over the next couple of days.

NASA's TRMM satellite data was used to create this 3-D flyby animation showing cloud heights and rainfall intensity on March 11. Cyclone Sandra's rainfall intensity was generally around 30 mm/1.18 inches per hour at the time of this flyover. Credit: NASA/SSAI, Hal Pierce


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



March 12, 2013

AIRS image of Sandra› Larger image
This infrared image of Cyclone Sandra was taken by the AIRS instrument aboard NASA's Aqua satellite on March 12 at 0235 UTC. The most powerful thunderstorms (purple) and heaviest rainfall appeared over the ocean. Credit: NASA JPL, Ed Olsen

MODIS image of Sandra› Larger image
The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA's Aqua satellite captured a visible image of Tropical Cyclone Sandra in the Coral Sea on March 11, 2013 at 23:50 UTC (9:50 p.m. EDT) showing the storm's southeastern quadrant was affecting New Caledonia. Credit: NASA Goddard MODIS Rapid Response Team
NASA Infrared Imagery Shows Dry Air Affecting Cyclone Sandra

Dry air wrapping around the northern and western quadrants of Cyclone Sandra are sapping its strength. NASA's Aqua satellite passed over Sandra and captured infrared imagery of the storm as it continues moving past New Caledonia.

An infrared image of Cyclone Sandra was taken by the AIRS (Atmospheric Infrared Sounder) instrument aboard NASA's Aqua satellite on March 12 at 0235 UTC. The infrared image showed that the most powerful thunderstorms and heaviest rainfall appeared over the ocean and west of the island. Cloud top temperatures were as cold as -63F (-52C) in the strongest thunderstorms. The AIRS data also revealed a band of strong thunderstorms east of the center that extended from central to northern New Caledonia.

Infrared satellite imagery on March 13 revealed that the bands of thunderstorms wrapping around Sandra's center had become disorganized. Sandra is encountering increasing vertical wind shear and cooler sea surface temperatures. The western and northern sides of the storm are also being impacted by dry air, which is sapping the moisture and limiting thunderstorm development.

On March 13 at 1500 UTC (11 a.m. EDT), Cyclone Sandra had maximum sustained winds near 75 knots (86.3 mph/138.9 kph). Sandra was located 250 nautical miles (287 miles/463 km) west of Noumea, New Caledonia, near 22.4 south and 161.9 east. Sandra was moving to the south at 10 knots (11.5 mph/18.5 kph).

At 1609 UTC (12:09 p.m. EST), Sandra continued to pull away from New Caledonia, and the Airport at Promenade Pierre Vernier, Noumea, reported a light misty rain with sustained winds from the east- northeast at 8.7 knots (10 mph/16.1 kph).

Sandra is expected to begin transitioning into an extra-tropical cyclone in the next two days as it moves farther south.

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



March 11, 2013

MODIS image of Sandra› Larger image
The MODIS instrument aboard NASA's Aqua satellite captured this visible image of Tropical Cyclone Sandra in the Coral Sea on March 10, 2013 at 23:10 UTC (7:10 p.m. EDT) as it nears New Caledonia. Credit: NASA Goddard MODIS Rapid Response Team.

AIRS image of Sandra› Larger image
This infrared image of Cyclone Sandra was captured on March 10 at 0247 UTC by the Atmospheric Infrared Sounder instrument aboard NASA's Aqua satellite. It shows cloud top temperatures, and strongest storms with coldest cloud-tops appear in purple. Note that the eye is visible. Credit: NASA JPL, Ed Olsen
NASA Sees Cyclone Sandra Threatening New Caledonia

NASA's Aqua satellite passed over powerful Cyclone Sandra twice as it approached the island nation of New Caledonia. Aqua's instruments provided visible and infrared looks at Sandra, revealing powerful thunderstorms around the center and a clear eye. Warnings are in effect in New Caledonia as Cyclone Sandra threatens heavy rain, surf and strong winds.

Aqua passed over Cyclone Sandra on March 10 at 0247 UTC and again at 23:10 UTC (7:10 p.m. EDT). Both times, the MODIS and AIRS instruments aboard captured visible and infrared images, respectively, of the storm.

The Atmospheric Infrared Sounder (AIRS) instrument aboard NASA's Aqua satellite provided scientists with an infrared look at Cyclone Sandra's cloud top temperatures on March 10 at 0247 UTC (March 9 at 10:47 p.m. EDT). The strongest thunderstorms circled the center of the eye, which was visible at that time. Infrared imagery showed that the strong thunderstorms had cloud top temperatures of -63F (-52C). Cloud tops that cold indicate powerful, high thunderstorms with the potential to drop heavy rainfall.

A visible image from the Moderate Resolution Imaging Spectrometer (MODIS) instrument taken later at 23:10 UTC (7:10 p.m. EDT) showed that Cyclone Sandra's eye had become cloud-filled, indicating possible weakening. The extent of the strong thunderstorms that AIRS imagery revealed early had lessened by the 23:10 UTC (7:10 p.m. EDT). The strong thunderstorms had also become somewhat more fragmented and less organized.

Cyclone Sandra's sustained winds reached 105 knots (121 mph/194.5 kph) early on March 11 weakened down to 90 knots (103.6 mph/166.7 kph) by 1500 UTC (11 a.m. EDT). At that time, Sandra was centered near 18.5 south latitude and 162.0 east longitude, about 350 nautical miles northwest of Noumea, New Caledonia. Sandra continued to move to the south-southeast at 5 knots (5.7 mph/9.2 kph).

Warnings are in effect for New Caledonia. The territory is on an Amber alert, specifically the extreme north of the mainland. On March 12 at 5:00 a.m. local time, the communities to the north of the line Ponérihouen-Pouembout will go on Amber alert; the communities of Koumac, Poum, Ouégoa and Bélep will go on Red Alert.

Sandra's center is expected to pass west of New Caledonia over the next two days while staying at sea. The eastern half of Sandra is expected to bring heavy surf, heavy rain and tropical-storm-force winds to New Caledonia with hurricane-force gusts as it passes by.

By March 14, Sandra is expected to transition into an extra-tropical storm and weaken over cooler and open waters of the Southern Pacific Ocean.

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



March 08, 2013

purple blobs bubble up through a blue-green soup, red-orange to the south. Outlines of australia can be seen to the southwest This infrared image of Cyclone Sandra was captured by the AIRS instrument that flies aboard NASA's Aqua satellite on March 8 at 1447 UTC (9:17 a.m. EST). Sandy's center and a band of thunderstorms east of center have strong (purple) thunderstorms dropping heavy rainfall. Credit: NASA JPL, Ed Olsen
› Larger image
NASA Satellite Sees Sandra Strengthening at Sea

Cyclone 19P in the Southern Pacific Ocean was renamed Sandra today, March 8, as NASA's Aqua satellite captured infrared data on the storm that indicated it would continue to strengthen. Residents of New Caledonia should prepare for impacts from Sandra early next week.

The Atmospheric Infrared Sounder (AIRS) instrument that flies aboard NASA's Aqua satellite captured an infrared image of Cyclone Sandra's cloud top temperatures on March 8 at 1717 UTC (12:17 p.m. EST). Strong thunderstorms around Sandra's center and in a band east of the center appeared as cold as -63 Fahrenheit (-52 Celsius), and are indicative of heavy rainfall.

As cloud tops grow taller in the troposphere, their temperatures grow colder (because temperatures drop with altitude in the troposphere). High cloud tops indicate a strong uplift of air that helps build the thunderstorms that make up a tropical cyclone. When uplift is strong, cloud tops sometimes punch through the top of the troposphere into the tropopause and even into the stratosphere.

Satellite imagery also showed central convection deepened (strengthened) over the storm's center since the previous day, indicating that Sandra is in a mode of strengthening.

Data from the Special Sensor Microwave Imager/Sounder (SSMIS) satellite instrument indicated an eye feature developing in Sandra early on March 8. Data from the SSMI is collected under the Defense Meteorological Satellite Program, which is a Department of Defense program responsible for designing, building, launching, and operating polar-orbiting environmental satellites.

On March 8 at 1200 UTC (7 a.m. EST/U.S.), Sandra's center was near 14.9 degrees south latitude and 157.7 degrees east longitude. The center of Cyclone Sandra was 645 nautical miles (742.3 miles/1,195 km) northwest of Noumea, New Caledonia. Sandra is moving to the east at 6 knots (7 mph/11.1 kph) and Sandra's maximum sustained winds had increased to near 60 knots (69 mph/111.1 kph).

Forecasters at the Joint Typhoon Warning Center noted on their update on March 8 that all environmental factors indicate that Sandra will continue to intensify over the next three days before weakening. Sandra is expected to pass west of New Caledonia on March 12, and bring heavy rain, possible flooding, strong winds and rough surf.

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



March 07, 2013

TRMM image of 19P› Larger image
NASA's TRMM satellite captured a look at the rainfall rates within System 92P on March 7 at 0023 UTC (March 6 at 7:23 p.m. EST) hours before it became a tropical cyclone. Red areas indicate heavy rain, falling at a rate of 2 inches/50 mm per hour. Green and blue areas indicate moderate rainfall. Credit: NASA/SSAI, Hal Pierce
NASA's TRMM Satellite Sees Tropical Cyclone 19P Form

NASA's Tropical Rainfall Measuring Mission satellite noticed areas of heavy rainfall in low pressure System 92P hours before it became the nineteenth tropical cyclone of the Southern Pacific Ocean.

NASA's TRMM satellite captured a look at the rainfall rates within low pressure System 92P on March 7 at 0023 UTC (March 6 at 7:23 p.m. EST), just hours before it became Tropical Cyclone 19P (TC 19P). TRMM data indicated that heavy rain was falling at a rate of 2 inches/50 mm per hour around the center of circulation, and that some of the thunderstorms were powerful as they topped heights of 9.3 miles (15 kilometers). Bands of thunderstorms around the storm expanded, strengthened and wrapped tighter around the storm's center today, March 7, according to the Joint Typhoon Warning Center (JTWC).

On March 7 at 1200 UTC (7 a.m. EST) the intensifying tropical storm had maximum sustained winds near 35 knots (40 mph/64 kph). TC 19P was centered near 15.4 south latitude and 156.9 east longitude about 660 nautical miles (759.5 miles/1,222 km) northwest of Noumea, New Caledonia. TC19P was moving to the east-northeast at 11 knots (12.6 mph/20.3 kph).

JTWC forecasters expect TC 19P to strengthen and curve to the southeast, affecting New Caledonia by March 11.

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