Aerial Observations of Hawaii's Wake

Under the influence of the east-northeasterly trade winds, the island of Hawaii generates a wake that extends about 200 km to the west-southwest. During the HaRP project in July and August 1990, five wake surveys were carried out by the NCAR Electra. The patterns of wind and aerosol concentration revealed by these flights suggest that Hawaii's wake consists of two large quasi-steady counterrotating eddies. The southern clockwise-rotating eddy carries a heavy aerosol load due to input from the Kī volcano. At the eastern end of the wake, the eddies are potentially warmer and more humid than the surrounding trade wind air. Several other features are discussed: sharp shear lines near the northern and southern tips of the island, dry and warm air bands along the shear lines, a small embedded wake behind the Kohala peninsula, wake centerline clouds, hydraulic jumps to the north and south of the island, a descending inversion connected with accelerating trade winds, and evidence for side-to-side wake movement.