Tuesday, January 1, 2002

Rain. The rain is back. And we are in for buffeting northeasterly winds tonight, heavy outflow winds which shouldn't affect us too much, although I am waiting for our first serious Squamish wind to see whether it passes over Collins Ridge behind us, or whether it swoops down over the ridge and through our back door. At this moment the weather station at Pam Rocks is showing 62 kph winds but stepping outside, you'd think it was a calm midsummer night with rain gently falling. The Vancouver weather report says the airport has light easterlies, at 7km/h. Pam Rocks is up Howe Sound a little, lying due east of Gambier Island and lies in the thick of the Squamish gale.

This kind of anamoly is not unusual in the winter in Howe Sound. To the north of us, three big valleys, the Squamish, Cheekeye and Mamquam Rivers converge at the head of the Sound. Each of these rivers rise in the glaciers that top the mountains to the north and east of us. As the ice sheets produce great volumes of water, they also create great amounts of cold air. The cold air runs, like the rivers, downhill. When it reaches sea level, having fallen 7000 feet or so in only a few miles, it has a fair head of steam on it. It carries on out of the Sound and washes across the Strait of Georgia where it sometimes creates an ennervating windchill in Nanaimo. If the cold outflow is amplified by an approaching low pressure system, while a high pressure system lies inland, the air is both pulled by gravity and pushed by pressure, squeezed off the continent, cascading down the pressure slope. When that happens, the windchills around here can get bracing and the Squamish winds can remained sustained for long periods of time, creating a swell in Howe Sound that buffets the ferry and sprays icy seawater across the car deck exposing cars to a winter's worth of Ontairo salt during the 20 minute crossing.

No comments:

Post a Comment