Fog

FTLComm - Tisdale - November 21, 2000

All across the Northern Grainbelt this morning we are enshrouded in fog. A truck who had left Melfort for Humboldt then came to Tisdale reported that they visibility was generally poor everywhere but the deceptively slipper highway surface was more of a concern. He said that it was hard to distinguish the level of traction available. Fog is produced when the temperature and the dew point ( point at which water condenses) become the same. When we look up and see a cloud that is the level where the water in the air turns visible. But there are other causes of fog. With

temperatures near or at dew point more fog is produced or generated with fast moving air. The picture at the top of this page and above illustrate this in a remarkable way. Visibility around Tisdale at 9:30 was half a mile but at North Steel Industries it was down to just under a car length. The source for the thick fog was the sand blasting operation. The compressed air released in the sandblasting process expands rapidly as it comes from the gun and as it does it absorbs a lot of heat from the already chilled air this further lowers the temperature of the surrounding air and the fog thickens proportionately. Through out the area frost is building up on the trees and this example below is a typical example of this morning's hoar frost.