On Sept. 14, 2016, the eye of Super Typhoon Meranti passed just south of Taiwan. The enormous storm, classified as a Category 5 typhoon at the time, still caused much disruption on the island. Nearly 500,000 homes lost power, schools were closed, and most flights were cancelled. Maximum wind speeds were 180 miles per hour (290 kilometers per hour) as the storm passed, and more than 25 inches (64 centimeters) of rain fell on some areas of the country. However, the storm did not pass over Taiwan's mountainous landscape, which would have weakened it. That means it will remain strong as it heads toward mainland China, unlike Super Typhoon Nepartak in July, which weakened from a Category 5 typhoon to a tropical storm after crossing Taiwan. Meranti is currently maintaining Category 4 strength and is expected to make landfall near Shantou, Guangdong province, on Thursday, September 15. The coast of China is more vulnerable to storm surges than Taiwan due to shallower coastal waters and recent rainfall. There is risk of substantial flooding.
On Sept. 14, at 10:45 AM local time, the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard NASA's Terra satellite passed directly over the eye of Meranti. On the left is a natural-color image from MISR's nadir-pointing camera. At this time the eye of Meranti was just off the southern tip of Taiwan, which is invisible under the clouds. The coast of China is barely visible through the clouds in the upper left portion of the image. The small eye and dense high clouds are both markers of the storm's power.
MISR's nine cameras, each pointed at a different angle, can be used to determine the heights of clouds based on geometric shifts among the nine images. The middle panel shows these stereo-derived cloud top heights superimposed on the natural color image. The clouds of the central core of Typhoon Meranti have heights ranging between 16 and 20 kilometers (10 and 12.5 miles). It takes about seven minutes for all nine cameras to image the same location on the ground, and wind velocity can be calculated from the motion of the clouds over this seven-minute period. The right panel plots these wind velocities as vectors which indicate both direction and speed. The length of the arrow corresponds to the wind speed, which can be compared to the reference 20 meters per second (45 miles per hour) arrow in the key. Hurricanes and typhoons in the Northern Hemisphere rotate counterclockwise due to the Earth's rotation, but these wind vectors mainly show motion outward from the eye at the storm tops. This is due to the fact that hurricanes draw in moist air at low altitudes, which then flows upwards and outwards around the eye reversing direction.
These data were acquired during Terra orbit 88865. Other MISR data are available through the NASA Langley Research Center; for more information go to http://eosweb.larc.nasa.gov/project/misr/misr_table. MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, California, for NASA's Science Mission Directorate, Washington, D.C. The Terra spacecraft is managed by NASA's Goddard Space Flight Center, Greenbelt, Maryland. The MISR data were obtained from the NASA Langley Research Center Atmospheric Science Data Center, Hampton, Virginia. JPL is a division of the California Institute of Technology in Pasadena.