During the second quarter of 2011, nearly all of the U.S. saw normal to above-normal wind speeds compared to long-term averages, according to data reported by AWS Truepower.
The greatest wind speed deviations were measured across the Rocky Mountains and southern Great Plains (over 25 percent above normal in some locations). Regions experiencing significantly below-normal wind speeds (by 5 percent to 10 percent) were limited to southern Georgia and Florida.
AWS Truepower said that during April, the weather phenomenon known as El Niño/Southern Oscillation (ENSO) weakened, but still remained in a negative phase (known as La Niña). It said a strongly positive North Atlantic Oscillation (NAO) and moderately negative Pacific-North American pattern (PNA) developed. In response to this pattern, a mostly zonal storm track persisted throughout much of the continental U.S., maintaining widespread normal or above-normal conditions.
Portions of the Pacific Northwest, Rocky Mountains, Southern Plains and Appalachians experienced wind speed deviations that were 20 percent or more above normal during April.
The ENSO index weakened during May and June and entered what the firm called a "neutral phase." During this period, the PNA moved to a slightly positive phase while the NAO entered into a moderate negative phase. In May the storm track shifted northward over much of the eastern U.S. and promoted relatively weak wind speeds throughout the Ohio River Valley, Mid-Atlantic and Northeast. All other regions experienced normal or above-normal wind speeds. In June the storm track became more zonal and wind farms throughout the much of the U.S. were windier than average. Below-normal wind speeds were limited to areas of the West Coast and New England.
The year that ended June 30 2011 showed near- or above-normal wind speeds across much of North America, with "significantly above-normal wind speeds" prevailing throughout the Rocky Mountains and Southern Plains (up to 15 percent above normal in some areas). This 12-month period differed from the previous year, when around half of North America experienced average or below-average wind speeds.
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