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Weather: Local Doppler will aid forecasts

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Doppler radar is an amazing thing. It can detect intense moisture up to 150 miles from the radar site. However, the range is closer to 90 miles to detect less intense rain and snow. Since Doppler radar is line-of-sight, the curvature of the earth leads to the radar beam "overshooting" cloud tops beyond this distance. The Doppler radar sites nearest Bemidji are located outside of Mayville, N.D., and at the Duluth International Airport, 115 and 135 miles distant, respectively.

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Being on the edge of the Doppler's range means that at times it might not be possible to accurately determine weather conditions in Bemidji. This is particularly troublesome during times of severe weather when the National Weather Service will also consult with on-the-ground observers to gather information.

Doppler radar also has its limitations. One is that since it works by essentially detecting motion, it can indicate storms where there are no storms. An example is the Ashtabula Wind Farm near Lisbon, N.D. The height of the wind turbines places them within site of the Mayville Doppler radar. A glance at that radar's returns will indicate what appears to be a stationary thunderstorm, but what is in reality the motion of the wind turbine's blades. While in its ultra-sensitive "clear air mode," Doppler radar near LaCrosse, Wis., has detected the hatching and first flight of the area's infamous mayflies.

The Bemidji Regional Airport is in the process of obtaining funding to install a Doppler radar to cover the Bemidji area.

Airport Director Harold Van Leeuwen is working with aeronautic interests in the area to cover the purchase costs. The state of Minnesota has agreed to fund the installation. The goal is to have installation complete by summer 2012. Having a local Doppler radar will provide much more accurate information for aviation and weather forecasting purposes in the area.

Tom Siemers is the Pioneer's circulation manager. Email him at tsiemers@bemidjipioneer.com

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