Unusual 2009 Weather Pattern Impacts Tornado Frequency and Wind Energy Production
Tornadoes are one of the most intriguing weather phenomena of the Plains and Midwest. These severe storms can occur just about anywhere in the U.S., but they tend to be concentrated in the region from Texas northward through South Dakota and Iowa – an area sometimes called “tornado alley.” This is the region where the two necessary ingredients for severe storms, abundant low-level moisture and vertical wind shear (changes in speed and direction with height), are most frequently found in the spring and early summer months.
Normal spring weather systems follow the jet stream from southwest to northeast across the Plains. This year, the weather systems moved from northwest to southeast pulling cool and dry Canadian air through the central United States. This created a situation in which the two main severe weather ingredients rarely came together. As a result, the number of tornadoes in tornado alley was approximately 75% below average from mid-May to mid-June. Many areas of the Northern Plains reported only 10-20% of the normal number of tornadoes during the peak of the season.
Related Impacts on Wind Energy Production — The anomalous spring 2009 weather pattern explains more than the lack of tornado reports. It also explains some atypical wind energy production across the central United States.
Over portions of the Central and Southern Plains, the position and orientation of the jet stream during May moderated the regional wind resource as the number of weather systems normally moving through the region was greatly reduced. Because of the northwest orientation of the jet stream, low-level jet activity (where higher-speed winds sometimes reach down to hub heights) was also below average. This weather pattern also curbed the July wind resource in the Southern Plains as it prevented the development of the western portion of the Bermuda High – an important feature for driving the Plains’ summer wind resource.
In contrast, these patterns intensified wind resources over the Northern Plains and Upper Midwest as the close proximity to the jet stream and stronger than average jet strength ushered more frequent and stronger weather systems through the area during the late spring and summer months.
These weather events clearly show the value of widespread geographic dispersion of wind plants and also highlight the need to carefully understand the long-term wind resource and variability. While unusual, the events of the past season are part of normal weather variability. For more information on managing wind variability, please contact Joe Sullivan at WindLogics.
Thanks to Dr. Cathy Finley, Senior Atmospheric Scientist, for this analysis.
Upcoming Events
WindLogics to Present at LAWEA Conference in Panama — Rolf Miller, Technical Consulting Services Manager, will be attending the second annual Latin American Wind Energy Association meeting (WIND EXPO 2009) in Panama this September. The conference theme is Integrating Wind Power into the Latin American Energy Matrix, and Rolf will be sharing “lessons learned” in the U.S. during two presentations:
- Managing the Impact of Wind Energy Variability through Integrated Forecasting
- Assessing the Impact of Wind Energy on the Electric Grid
The areas of greatest wind energy potential in Latin America are located in Brazil, Central America and the Caribbean islands. WindLogics has completed projects in all of these areas, including off-shore mapping in the southern Atlantic Ocean.
Wind Resource & Project Energy Assessment Workshop, Minneapolis — Look for WindLogics at this American Wind Energy Association workshop, scheduled for September 30 and October 1 and focusing on techniques for pre- and post-build energy assessment.
WindLogics CEO Mark Ahlstrom will be moderating the session on post-construction Operational Assessment, and our key research staff and senior management will also be participating throughout the conference. If you are planning to attend and would like to visit with any of our staff, please contact Larry Sinesio to arrange a meeting convenient to your schedule.
