Featured Images

Text Size

Hurricane Season 2011: System 91W (Northwestern Pacific Ocean)
03.04.11
 
System 91W is the small blue and purple area in the South China Sea. › View larger image4
NASA's Aqua satellite AIRS instrument captured remnants of System 91W on March 4 at 05:29 UTC (12:59 a.m. EST). System 91W is the small blue and purple area in the South China Sea. The small area of purple in the middle of the image indicates strong thunderstorms still exist.
Credit: NASA/JPL, Ed Olsen
NASA's Aqua Satellite Watches System 91W Dissipate

The low pressure area called System 91W that showed some promise of developing into the first tropical depression of the Northwestern Pacific hurricane season has dissipated. NASA's Aqua satellite revealed some bursts of strong convection in its death throes earlier today.

NASA's Aqua satellite Atmospheric Infrared Sounder (AIRS) instrument captured remnants of System 91W on March 4 at 05:29 UTC (12:59 a.m. EST). The remnants of System 91W were just a small area in the South China Sea that stretched from west to east. It was last located near 10.4 North latitude and 113.2 East longitude. When AIRS captured an infrared image of the low's cloud top temperatures early today there was a small area of strong convection (rapidly rising air that forms the thunderstorms that power a tropical cyclone) where strong thunderstorms still existed.

By late morning on March 4 (Eastern Standard Time) System 91W had dissipated and was no longer suspect for development into a tropical depression.

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



March 3, 2011

AIRS caught the western edge of the low pressure area (purple) that appears more organized and rounded. › View larger image
On Mar. 2 at 1753 UTC, NASA's Aqua satellite captured what appeared to be a disorganized low pressure area (left). On March 3 at 0623 UTC (right) Aqua caught the western edge of the low pressure area (purple) that appears more organized and rounded. On March 3, Aqua satellite flew west of its center so the eastern half of the storm was out of the satellite's view (light blue area).
Credit: NASA/JPL, Ed Olsen
NASA's Aqua Satellite Watching a Tropical Low in the South China Sea

A low pressure area designated as System 91W in the South China Sea has shown some bursts of strong convection, and an infrared instrument on NASA's Aqua satellite has been watching it for possible tropical development.

The South China Sea is part of the Pacific Ocean, that stretches from the Singapore and Malacca Straits to the Strait of Taiwan.

On Mar. 2 at 1753 UTC (12:53 p.m. EST), the Atmospheric Infrared Sounder (AIRS) instrument that flies aboard NASA's Aqua satellite captured what appeared to be a disorganized low pressure area with some strong areas of convection (rapidly rising air that condenses and forms the thunderstorms that power a tropical cyclone). AIRS measured the temperatures in those strong areas of convection and found they were as cold as or colder than -63 Fahrenheit (-52 Celsius). On March 3, at 0623 UTC (1:23 a.m. EST) caught the western edge of the low pressure area that appeared slightly more organized and rounded, as the Aqua satellite flew west of its center, however, convection seemed to be weaker.

System 91W is now about 340 nautical miles (629 km) northwest of Brunei, near 10.4 North latitude and 113.2 East longitude. NASA's AIRS imagery should that the low level circulation center became fully exposed mid-day today, March 3, 2011 (Eastern Standard Time), and convection had weakened from earlier satellite overpasses.

An upper level analysis from the Joint Typhoon Warning Center (JTWC) today indicated that the low-level center was in an area of moderate to high vertical wind shear, blowing at about 25 knots (29 mph/46 kmh). Wind shear weakens a tropical cyclone, or a low pressure area. Currently, the maximum sustained surface winds from System 91W were between 10 and 15 knots (11 to 17 mph/18 to 27 kmh. The JWTC currently gives System 91W a poor chance of becoming a tropical depression in the next 24 hours, but NASA's AIRS instrument will keep taking its temperatures to monitor its strength.

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