Wind speeds were above their seasonal averages in most of the continental U.S. last year, according to 3TIER's recently released wind performance map, which covers the entire year of 2011.
The map shows departures of -20% to +20% from long-term mean wind speeds and provides an indication of how wind projects should have performed relative to their long-term production average based on their location. This type of analysis enables financiers and owners to perform portfolio analysis across regions and quickly view the effects of weather anomalies on both existing and proposed investments.
For the year as a whole, the U.S. experienced above-average wind speeds, though month-to-month and regional variability were not uniformly above average across the country. The Pacific Northwest and New England saw wind speeds roughly 5% below average for the year, while a broad section of the U.S. – from northern Montana to Texas and the Mid-Atlantic states – enjoyed a strong wind year, with wind speeds 5% to 15% above normal.
The year began with weak La NiÃ±a conditions and lackluster wind speeds. However, a stronger La NiÃ±a, which occurred later than initially forecasted, combined with a negative Pacific/North America pattern, led to increased wind speeds throughout the spring.
Summer winds were particularly strong in the Southern states, where warm and dry conditions continued under a large upper-level ridge that suppressed winds further north. The ridge persisted into September, when the central and eastern U.S. moved back into a more vigorous weather pattern, with frequent frontal passages contributing to higher-than-normal wind speeds.
By the end of 2011, the North Atlantic Oscillation was in a positive phase, associated with lower-than-normal winds in the western U.S. The effects of this trend dominated those of the persistent La NiÃ±a state in the equatorial Pacific. However, winds were above normal for most of the country east of the Rocky Mountains, except in the northeastern U.S., where upper-level ridging kept temperatures warm and wind speeds low.
The wind performance map was created by comparing output from 3TIER's continually updated meteorological data set with wind conditions averaged over the period from 1969 to 2008 from the same data set. Wind-speed values were computed using a numerical weather prediction model run at a 15 km resolution and adjusted using available observations.
The full map can be viewed here.