NASA's Aqua satellite passed over Tropical Storm Sonca as it began making landfall in Vietnam. Aqua gathered temperature data using infrared light that showed the extent of the strongest storms. Those storms were generating heavy rains that were expected to affect Vietnam, Thailand and Laos.
The Atmospheric Infrared Sounder or AIRS instrument aboard NASA's Aqua satellite analyzed Tropical Storm Sonca in infrared light on July 24 at 1:41 a.m. EDT (0541 UTC). Infrared light provides scientists with temperature data and that's important when trying to understand how strong storms can be. The higher the cloud tops, the colder and the stronger they are. So infrared light as that gathered by the AIRS instrument can identify the strongest storms within a tropical cyclone.
AIRS infrared data showed an area of strong storms with cloud top temperatures as cold as minus 63 degrees Fahrenheit (minus 53 degrees Celsius) around the center as the western quadrant of the storm was already over the Vietnam coast. NASA research has shown that cloud tops that cold, which are high in the troposphere, have the ability to generate heavy rainfall.
By 5 a.m. EDT (0900 UTC) on July 25, Sonca had made landfall and the Joint Typhoon Warning Center issued their final warning on the system. At that time, Sonca was located about 87 miles northwest of Da Nang, Vietnam near 17.0 degrees north latitude and 107.2 degrees east longitude. It made landfall with maximum sustained winds near 40 knots (46 mph/74 kph) and was moving west at 12 knots (13.8 mph/22.2 kph).
Sonca is expected to dissipate inland but will continue to bring heavy rainfall over Vietnam, Thailand and Laos. The Thailand Meteorological Department warned that as Sonca continues to move west, it will bring heavy rain to most of Thailand from July 25 to 28.
For updated forecasts from Vietnam's National Center for Hydro-Meteorological Forecasting (NCHMF), visit: http://www.nchmf.gov.vn/web/en-US/43/Default.aspx
For updated forecasts and warnings from the Thailand Meteorological Department, visit:
By Rob Gutro
NASA's Goddard Space Flight Center