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Hurricane Season 2011: Tropical Storm Sonca (Western North Pacific Ocean)
09.20.11
 
TRMM saw moderate rainfall throughout Sonca on Sept. 18 at 1805 UTC. › View larger image
TRMM saw moderate rainfall throughout Sonca on Sept. 18 at 1805 UTC. Red areas are heavy rainfall at 2 inches (50 mm) per hour. Yellow and green areas indicate moderate rainfall between .78 to 1.57 inches (20 to 40 mm) per hour.
Credit: NASA/SSAI, Hal Pierce
NASA's TRMM Satellite Sees Heavy Rainfall Wane in Tropical Storm Sonca

The Tropical Rainfall Measuring Mission (TRMM) satellite captured a look at the rainfall occurring in Tropical Storm Sonca and noticed only heavy rainfall in its southwestern quadrant on Sept. 18. Afterward, Sonca moved through cooler waters and weakened and mostly produced moderate rainfall while becoming extra-tropical.

TRMM captured an image of Typhoon Sonca's rainfall when it was off the east coast of the main Japanese island of Honshu at 1805 UTC (2:05 p.m. EDT) on Sept. 18, while moving away from Japan toward the north-east. TRMM saw moderate rainfall throughout Sonca falling at a rate between .78 to 1.57 inches (20 to 40 mm) per hour. Sonca was still a powerful typhoon with wind speeds of about 85 knots (~98 mph) at that time pass but Sonca weakened to a tropical storm on September 19, 2011 while moving over the colder waters of the northern Pacific Ocean to the north-east of Japan.

On Sept. 20 the Joint Typhoon Warning Center issued their final advisory on the weakened Tropical Storm Sonca at 0300 UTC (11 p.m. EDT Sept. 19). At that time, Sonca's maximum sustained winds had decreased from typhoon strength down to 60 knots. It was moving to the east-northeast at 32 knots and away from land areas. Its center was about 650 miles east of Misawa, Japan near 39.9 North and155.5 East. Sonca will continue moving northeast into the North Pacific Ocean and finish transitioning to an extra-tropical storm at sea.

Text credit: Hal Pierce/Rob Gutro,
SSAI/NASA Goddard Space Flight Center, Greenbelt, Md.



September 19, 2011

This infrared image from AIRS shows Tropical Storm Roke (left) and Tropical Storm Sonca (right). › View larger image
This infrared image from the AIRS instrument on NASA's Aqua satellite from Sept. 19 at 12 a.m. EDT, shows Tropical Storm Roke (left) about 630 miles southwest of Yokosuka, Japan, and Tropical Storm Sonca (right) about 395 miles ESE of Misawa, Japan. The purple areas are as cold as -62F/-52 C and are where the strongest thunderstorms and heaviest precipitation is occurring.
Credit: NASA/JPL, Ed Olsen
This visible image from the AIRS instrument shows Tropical Storm Roke (left) and Tropical Storm Sonca (right) › View larger image
This visible image from the AIRS instrument of Tropical Storm Roke (left) and Tropical Storm Sonca (right) shows that the cloud cover extends further than what is seen on infrared, as infrared reveals the highest, coldest cloud heights.
Credit: NASA/JPL, Ed Olsen
This image of Typhoon Sonca was captured on Sept. 18 at 03:20 UTC (Sept. 17 at 11:20 p.m. EDT) › View larger image
This image of Typhoon Sonca was captured on Sept. 18 at 03:20 UTC (Sept. 17 at 11:20 p.m. EDT) as it was making its way past Japan in the western North Pacific Ocean.
Credit: NASA Goddard MODIS Rapid Response Team
NASA Satellite Sees Two Tropical Systems Near Japan

NASA's Aqua satellite captured infrared and visible images of two tropical cyclones near Japan today. Typhoon Roke is near extreme southeastern Japan, while Typhoon Sonca is near east central Japan. Roke is expected to make landfall, while Sonca is not.

NASA infrared images and the visible images tell different stories. The infrared imagery taken from the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite takes cloud temperatures, which tell a lot about the system. The colder the cloud top temperature, the higher and stronger the thunderstorms within the storm. That means more uplift or energy in the storm. Wherever the coldest, highest cloud tops are, that's where the heaviest rains are likely falling.

In Roke, AIRS infrared imagery showed a large area concentrated around the storm's center. Infrared satellite imagery also showed deepening convective (thunderstorm) bands wrapping into a ragged eye. In Sonca, the area of strongest thunderstorms was not as large when AIRS captured an image on Sept. 19 at 12 midnight (EDT). That suggests that Roke has more power than Sonca. In addition, convection on Sonca's northern edge appears to be weakening.

The visible images help show that the cloud shield for these tropical cyclones extend further than the infrared images show. That's because the fringes of the storms may have lower, less powerful thunderstorms.

At 11 a.m. EDT on Sept. 19, Typhoon Roke had maximum sustained winds near 70 knots (80 mph/129 kmh). Those typhoon-strength winds extended 20 miles (32 km) from the center, while tropical-storm force winds extend out 110 miles from the center. So, the strongest winds were only about 40 miles (64 km) in diameter. Roke is about 220 miles (354 km) in diameter. Roke was located about 635 miles(1022 km) southwest of Yokosuka, Japan near 28.3 North and 130.4 East. The storm surge with Roke is expected to be strong as Roke is currently generating 26-foot high waves in the western North Pacific Ocean.

Stars and Stripes.com reported that at 4:30 p.m. local time in Japan on Monday, Sept. 19, Tropical Cyclone Condition of Readiness 3 was set for Yokosuka Naval Base at 4:04 p.m. and at 6 p.m. local time for the Naval Air Facility Atsugi. Roke's winds are expected to start affecting Yokosuka on Tuesday. Kyushu is under a tropical cyclone warning. Kyushu is the third largest island of Japan and southwest of Japan's four main islands. Warnings and watches can be found on the Japan Meteorological Agency's web page: http://www.jma.go.jp/en/warn/.

Roke is expected to move northeast and is currently forecast to make landfall near Kyoto and track inland. It will begin to weaken because of vertical wind shear and then move back out into cooler water in the western North Pacific by 1200 UTC (8 a.m. EDT) on Sept. 21.

Typhoon Sonca is about 395 miles (635 km) east-southeast of Misawa, Japan near 27.5 North and 148.8 East. Sonca's maximum sustained winds have increased to 75 knots (86 mph/138 kmh) and the storm is becoming extra-tropical. It is moving to the northeast and away from Japan at 26 knots. Sonca is a compact storm and not as large as Roke. Sonca also has a small, irregular-shaped eye. Infrared imagery showed that convection on the northern edge of the storm is weakening, as cloud temperatures are warmer. Sonca's tropical-storm force winds extend to about 90 miles (144 km) from the center making it about 180 miles (289 km) in diameter. Interestingly enough, the typhoon-force winds cover the same distance as Roke, about 40 miles (64 km) in diameter. Sonca is moving northeast as it undergoes extra-tropical transitioning to the east of Japan.

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



Sept. 16, 2011

TRMM saw moderate rainfall in Tropical Storm Sonca on Sept. 16, 2011 at 9:26 a.m. EDT. › View larger image
saw moderate rainfall in Tropical Storm Sonca on Sept. 16, 2011 at 9:26 a.m. EDT. Yellow and green areas indicate moderate rainfall between .78 to 1.57 inches (20 to 40 mm) per hour.
Credit: NASA/SSAI, Hal Pierce
NASA's TRMM Satellite Sees Moderate Rainfall Tropical Storm Sonca

When the Tropical Rainfall Measuring Mission (TRMM) satellite flew over Tropical Storm Sonca on Friday, Sept. 16 it found moderate rainfall mostly on the southern side of the storm. Chichi Jima can expect some of that rainfall over the weekend as Sonca passes east of the island.

TRMM passed over Tropical Storm Sonca and its precipitation radar instrument saw moderate rainfall occurring mostly on the southern side of the storm, while light-to-moderate rainfall was occurring throughout the storm. The southern edge of the storm had rainfall rates between .78 to 1.57 inches (20 to 40 mm) per hour. The TRMM satellite is managed jointly by NASA and the Japanese Space Agency.

At 11 a.m. EDT on Sept. 16, Tropical Storm Sonca had maximum sustained winds near 45 knots (52 mph). It was centered about 500 nautical miles east of Iwo To, Japan, near 23.5 North and 149.4 East. Sonca was moving to the west at 15 knots.

NASA's Aqua satellite has been flying over Sonca, and the Atmospheric Infrared Sounder (AIRS) instrument has been providing infrared imagery and temperature data of the storm. Infrared imagery has shown convection (rapidly rising air that forms the thunderstorms that power the tropical cyclone) around Sonca's center, in addition to bands of thunderstorms wrapping into the center. There is, however a good amount of dry air streaming into the western quadrant of the storm, which suppresses thunderstorm development. Infrared data has also shown that the sea surface temperatures are around 27 Celsius (just over 80 Fahrenheit) and warm enough to maintain a tropical cyclone.

The Joint Typhoon Warning Center has forecast Tropical Storm Sonca to make an easterly pass by the island of Chichi Jima over the weekend and then head to the northeast into the open waters of the western North Pacific Ocean.

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



Sept. 15, 2011

satellite image of Sonca › View larger image
This infrared image of Tropical Storm Sonca was captured on Sept. 14 at 10:41 p.m. EDT. The purple area around the center of circulation indicates the coldest, highest cloud heights, where the heaviest rain was occurring. Satellite data also shows Sonca has taken on the signature "comma" shape of a tropical storm.
Credit: NASA JPL, Ed Olsen
Infrared NASA Satellite Imagery Confirmed Newborn Tropical Storm Sonca

Infrared satellite imagery from NASA's Aqua satellite yesterday showed powerful convection building in the low pressure area known as System 94W and provided forecasters with an inside look that the low was strengthening. System 94W did intensify and became Tropical Storm Sonca today.

Infrared imagery is gathered by the Atmospheric Infrared Sounder (AIRS) instrument that flies on NASA's Aqua satellite. It provides valuable information to forecast organizations such as the Joint Typhoon Warning Center and National Hurricane Center about cloud temperatures and heights and sea-surface temperatures.

Infrared data provides valuable clues about how a tropical cyclone is going to behave. High, cold clouds with temperatures colder than -63 Fahrenheit (-52 Celsius) within a tropical cyclone tell meteorologists that convection (rising air that forms thunderstorms that power a tropical cyclone) is strong, and further strengthening of the entire tropical cyclone is likely. When NASA satellites show that cloud temperatures are warming, it means there is less strength or uplift in the air to help form powerful thunderstorms.

When NASA's Aqua satellite flew over Tropical Storm Sonca on Sept. 14 at 10:41 p.m. EDT the AIRS instrument gathered that infrared temperature data about the thunderstorms that make up the storm. AIRS showed a large area around the center of circulation where the coldest, highest cloud heights, where the heaviest rain was occurring. Satellite data also showed Sonca has taken on the signature "comma" shape of a tropical storm.

Tropical Storm Sonca's maximum sustained winds are near 35 knots (40 mph) so it's just over the threshold of being a tropical storm. The storm is over 120 miles in diameter with tropical storm-force wind gusts out 60 miles from the center. Sonca is approximately 760 nautical miles east of the island of Iwo To, Japan and has tracked north-northwestward at 9 knots (10 mph).

Forecasters at the Joint Typhoon Warning Center are monitoring the progress of Sonca and using the infrared data that AIRS provides in addition data from other NASA satellites. Sonca is currently forecast to pass to the northeast of Chichi Jima, Japan over the weekend and bring gusty winds, heavy surf and rainfall to the island.

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



September 14, 2011

This infrared image of System 94W was taken on Sept. 14 at 1:59 UTC and it appears disorganized. › View larger image
This infrared image of System 94W was taken on Sept. 14 at 1:59 UTC and it appears disorganized (and not circular). The bulk of showers and clouds appear to be on the east side of the center of circulation.
Credit: NASA/JPL, Ed Olsen
NASA Sees Strong Convection in System 94W, Organizing Tropically

A low pressure area formed in the same area where Tropical Storm Roke formed last week, and infrared data from NASA's Aqua satellite revealed strength in convection and thunderstorms to the east of the storm's center.

System 94W's center of the circulation is hard to pick out in satellite data, but is likely west of a large area of clouds and rain. The Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite captured an infrared image on Sept. 14 at 1:59 UTC (Sept. 13 at 9:59 p.m. EDT). AIRS showed what appeared to be a comma-shaped area of strong convection (rapidly rising air that condenses and forms clouds and showers) east of the center. That area is also where AIRS measured the coldest cloud-top temperatures, indicating the thunderstorms are highest and rainfall is likely heaviest. There are also broken or isolated areas of convection north of the storm's center. Forecasters will be watching the infrared data to see if the area of strong thunderstorms expands as the low pressure area continues to develop.

The Joint Typhoon Warning Center (JTWC) places System 94W's center near 20.9 North and 154.3 East. That's 595 miles northeast of Saipan. The low is moving to the northwest at 7 knots (8 mph/13 kmh) and has maximum sustained winds as high as 23 knots (26 mph/42 kmh). The JTWC noted that atmospheric and sea surface temperatures (warmer than 28 Celsius/82 Fahrenheit) are conducive to helping System 94W get more organized, and it has a high chance of becoming a tropical depression in the next 24 to 36 hours.

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