Wind speeds in Canada and the Northern U.S were 10% to 20% below average but 5% to 10% above average across most of the southern and western U.S. for the fourth quarter of 2012, according to Albany, N.Y.-based AWS Truepower's quarterly Wind Trends bulletin.
In North America, AWS notes wind speed anomalies at 80 m above ground level exhibited a pronounced north-south pattern across North America during the fourth quarter. The monthly wind speed deviations across North America varied substantially throughout the quarter, as storm tracks and upper-level features shifted with the approach of the winter season.
In October, the weather in North America was dominated by a blocking pattern consisting of strong persistent high-pressure systems in the Bering Sea and North Atlantic and a deep trough centered in the midwestern U.S., the company notes.
The resulting storm track increased wind speeds 15% to 25% higher than average in the Mississippi and Ohio River valleys. In November, however, winds were 15% to 25% below average across the same region, as a persistent ridge replaced the upper-level trough.
Wind speeds across much of the rest of North America were flat to modestly below-average during this time. December brought yet another pattern shift, with persistent low pressure over the western half of the continent and persistent high pressure centered over Labrador, Canada.
Several winter storms brought much-higher-than-average wind speeds – in some cases, 30% above average – to the western U.S., while the northern Great Plains, Great Lakes and much of Canada experienced wind speeds 10% to 20% below average.