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High-Pressure Cloud Hole: Earth Image of the Week June 15, 2012
High pressure cloud hole image from south of Australia.
Downward motion of the air around a high-pressure area caused this large hole to appear in the cloud deck south of Australia.
An expansive hole in an otherwise cloud-covered ocean startled satellite image observers in early June, but the reason for its appearance was easy to explain.

The 600-mile-wide oval-shaped opening in the marine stratocumulus cloud deck just south of mainland Australia exposed the open water of the Great Australian Bight.

It is clearly visible in the image to the right, captured by NASA’s Aqua satellite at about 3 p.m. local time on June 5.

Sea-level pressure maps prepared by the Australian Bureau of Meteorology show that the cloud hole matched the shape of a high pressure area blanketing the region, and global weather models had accurately predicted it.

High pressure is typically associated with sinking and drying air, which is also responsible for most spells of fair weather.

Low pressure generally does the opposite, lifting air and creating clouds that bring precipitation.

The center of the high-pressure area associated with the June 5 clearing didn’t match it precisely, according to NASA.

The center of the high was near the western edge of the clear area, about 60 miles from the cloud edge.

“You could call it an anti-storm,” quipped NASA Langley atmospheric scientist Patrick Minnis.

Full story and image: NASA