image: This infrared image shows Tropical Depression Haitang's coldest clouds (purple) and strongest thunderstorms. It was captured from the AIRS instrument on NASA's Aqua satellite on Sept. 26 at 0541 UTC. The much larger Typhoon Nesat is to the right over Luzon, Philippines. view more
Credit: NASA/JPL, Ed Olsen
Very cold temperatures in NASA infrared satellite imagery of tropical cyclones tell meteorologists that cloud tops are high, and the thunderstorms they're associated with have a lot of punch. Some of those strong storms are evident in Tropical Depression Haitang as it heads for landfall in Vietnam where cloud-top temperatures exceed -63 Fahrenheit.
At 5 a.m. EDT on Sept. 26, Tropical depression Haitang was centered near 16.8 North and 110.5 East. That's about 170 miles east of Hue, Vietnam. Haitang had maximum sustained winds near 30 knots (35 mph/55 kmh). It was moving to the west near 6 knots (7 mph/11 kmh) and generating 12-foot high waves in the Gulf of Tonkin.
When NASA's Aqua satellite flew over Haitang on Sept. 26 at 0541 UTC (1:41 a.m. EDT/12:41 p.m. local time Vietnam) the Atmospheric Infrared Sounder instrument took an infrared snapshot of the storm. Infrared data shows temperatures, and the coldest temperatures and strongest thunderstorms (and heaviest rainfall) was located west of Haitang's center. Haitang is battling strong wind shear blowing from the east and pushing the strongest storms to the west of the center.
The center is also fully exposed to those winds, meaning its prime for further weakening. The center also appears to be slightly elongated, and whenever a storm isn't stacked on top of itself, it loses energy. Satellite imagery also shows that the convection (rapidly rising air that forms the thunderstorms) is disorganized, so further weakening may be possible before landfall.
Haitang is expected to make landfall near Hue, Vietnam tomorrow and dissipate within a day.