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Bad Summer?


July 20, 2009 — Itís true. The first month of summer has been cooler and wetter than usual in many parts of Canada.

The Great Lakes region, Prairies and Maritimes have felt the cool and wet rejection of this season the most.

A few facts: Toronto, Montreal and Winnipeg have been 2 to 4 degrees below average almost day in, day out since the season began. Halifax nearly doubled its average June rainfall. Days with more cloud cover than sun were common nearly all across Canada.

There are exceptions, and these are equally significant. Vancouver and St Johnís have had one of their sunniest, warmest and driest seasons to date.

In typically smoggy regions the number of smog days can be counted on one hand (not using your thumb). Power consumption is lower because air conditioning isnít needed.

The rest of the summer, August at least, will be very close to average for nearly all of the country. The temperature should be where it ought to be but it is likely that cloudier and rainier days might prevail in the east.

In eastern Canada, first impressions are lasting ones, and so it goes for this summer. As pleasant as the rest of the season might be, our collective memory will likely file this summer as not so great.

Why?

Science is investigating the weather pattern over North America and the weather weíve had during the first part of our summer has a lot to do with something called the North Atlantic Oscillation, a pattern uncovered in the 1920ís by Sir Gilbert Walker.

The North Atlantic Oscillation is a variance in the location of a large area of strong and stable high pressure. For the past many weeks it has developed over Greenland and the Labrador Sea.

The emergence of the North Atlantic Oscillation has lead to a block in the usual, steady west to east migration of unsettled low pressure across our continent.

Simply, the cool rainy weather is stopped once it gets to the Great Lakes Basin because it cannot get past the big, stable high pressure over the western Atlantic. Not until the high pressure, that has manifested itself further east, relaxes will there be a change in the pattern.

While science continues to study the underlying reasons for the temperament and frequency of the oscillation, we can report that it is easing and more typical summer weather is returning to eastern Canada.

Chris St. Clair
No one knows the importance of accurate weather forecasts more than Chris St. Clair. The weather savvy St. Clair joined The Weather Network in 1996 and currently reports fair or foul skies every Saturday and Sunday from 6 a.m. to 3:00 p.m. on This Weekend. A self-confessed weather, climate and geography enthusiast, St. Clair is well-known by viewers for his thorough weather reports.

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