NASA's Aqua satellite passed over the South China Sea and obtained a visible light image of the first depression of the Northwestern Pacific Ocean basin's 2018 tropical cyclone season. Vertical wind shear can be deadly to tropical cyclones and satellite data showed Tropical Depression Bolaven, formerly known as 01W, was being adversely affected by it.
On Jan. 3 at 1:10 a.m. EST (0610 UTC) the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard Aqua provided a visible look at the effect wind shear was having on Bolaven. Southeasterly wind shear had pushed the bulk of clouds to the northwestern quadrant of the storm, leaving the rest of the circulation exposed and with just fragmented clouds.
On Jan. 3 at 10 a.m. EST (1500 UTC), Tropical Depression Bolaven was located near 11.7 degrees north latitude and 112.6 degrees east longitude, about 391 nautical miles east of Ho Chi Minh City, Vietnam. Bolaven's maximum sustained winds were near 30 knots (34.5 mph/55.5 kph). The depression was moving to the west-northwest at 16 knots (18.4 mph/29.6 kph).
The Joint Typhoon Warning Center said Bolaven will continue to weaken due to persistent vertical wind shear and cooler sea surface temperatures as it approaches Vietnam. Once the storm makes landfall, it expected to dissipate rapidly as it tracks inland.
The forecast calls for Bolaven to track west across the South China Sea and will not intensify before making final landfall in southern Vietnam on Jan. 4.