Tropical Storm Atsani appeared elongated when NASA's Terra satellite passed overhead. Atsani weakened to a tropical storm on August 24, 2015.
On Aug. 24 at 11:40 (7:40 a.m. EDT) the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA's Terra satellite captured infrared data on Tropical Storm Atsani. Atsani appeared to be somewhat elongated from southwest to northeast. Infrared data also showed that the eastern quadrant appeared almost devoid of thunderstorm activity. However, the other quadrants of the storm maintained powerful thunderstorms with cold cloud top temperatures near -63F/-53C. The coldest cloud tops appeared south of the center of circulation.
Although the southern part of the tropical storm is under low to moderate vertical wind shear, the northern part of the storm is dealing with stronger wind shear and is interacting with the westerlies (winds).
At 1500 UTC (11 a.m. EDT) on August 24, Tropical Storm Atsani had maximum sustained winds near 65 knots (75 mph/120 kph). It was centered near 32.9 North latitude and 150.8 East longitude, about 570 nautical miles (655.9 miles/1,056 km) south-southwest of Yokosuka, Japan. Atsani was moving to the east-northeast at 14 knots (16.1 mph/25.3 kph).
Forecasters at the Joint Typhoon Warning Center (JTWC) noted that sea surface temperatures will drop below 26.6 Celsius (80 Fahrenheit) over the 12 to 24 hours from 1500 UTC (11 a.m. EDT) on August 24. When sea surface temperatures fall below that threshold, a tropical cyclone cannot sustain strength. JTWC expects that Atsani will then begin changing to an extra-tropical storm.