A large high pressure system occupied the lower Arctic Ocean from the Chukchi Sea to the Beaufort Sea. SHEBA ship was on the north side of this high with westerly winds. A dense cloud mass over the ship was thinning during the afternoon (see the radar ). Cloud bases rose to about 5 km by 00 UT. The radar reported cloud tops at 10.5 km. The GLAS rawinsonde stopped reporting when the sonde entered the cloud. The GLAS sounding reported high humidity in the lowest km, but the ship weather reports did not indicate any fog or visibility obstructions.
The trajectories to SHEBA ship show the low level air, surface-1.5 km, coming from the Alaskan coast including Barrow and circling around the Chukchi Sea. The 3.0 km air came from Siberia to the southwest and the highest levels, 6-9 km, air came from central Asia, farther west.
