During the second quarter of 2011, nearly all of the contiguous United States experienced normal to above-normal wind speeds compared to the long-term average for the same quarter. The greatest deviations occurred throughout the Rocky Mountains and southern Great Plains (over 25% above normal in some locations). Regions experiencing significantly below-normal (by 5% to 10%) wind speeds were limited to southern Georgia and Florida. During April, the El Niño/Southern Oscillation (ENSO) weakened considerably but still remained in a negative phase (La Niña). Meanwhile, 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 United States, 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% or more above normal during this month.
The ENSO index weakened throughout May and June and entered a neutral phase. During this period, the PNA transitioned into 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 United States 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 United States were windier than average. Below-normal wind speeds were limited to small areas of the West Coast and New England.
The year ending 30 June 2011 (Q2 2011) exhibited near- or above-normal wind speeds throughout much of North America, with significantly above-normal wind speeds prevailing throughout much of the Rocky Mountains and Southern Plains (up to 15% above normal in select local areas). This 12-month period is sharply different from the previous year (ending 30 June 2010), when about half of North America experienced average or below-average wind speeds. Data for this analysis came from AWS Truepower’s Wind Trends product, a validated database of weather conditions dating back to 1997. Wind Trends provides a weather snapshot at multiple heights above ground for every hour. Maps, data and monthly reports for wind resource deviations, updated on a monthly basis, are available by subscription to windNavigator Asset Management.
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