The NEXRAD Doppler Radar and Bats…

doppler-1-640x380The great joys of new observational tools include unintended consequences. I can relay a story about the WSR-88D (NEXRAD) Radar to illustrate this.

As a new Warning Coordination Meteorologist at the National Weather Service in 1991 in Norman, Oklahoma, a group of us were the first to be allowed to use the new radar. We knew it would be a great tool to observe and warn for thunderstorms, tornadoes and heavy rain. The contractor turned the radar over to us on March 20, 1991, and we had our first severe weather outbreak the next day, as severe thunderstorms producing tornadoes moved across the Ada, Oklahoma area.

We were amazed at what we could see, but as with most new observational tools, as many or more questions were raised as answered. As we got into the summer, we noticed that around sunset, in locations in both southwest and northwest Oklahoma, a “dot” would appear on the radar in particular locations. The dots would grow into an open circle and disappear. A few curious NWS forecasters decided to make a trip to southwest Oklahoma to check out what was happening.

Their findings were astonishing. They found thousands of bats leaving a cave at sunset, and this was detected by the new radar! The findings were written up, and bat enthusiasts, as well as people who studied bird migrations and even butterflys, had a new tool to use.

Here is a recent example of what the “bat” image looks like. The image is from the Austin-San Antonio radar at New Braunfels, Texas. You’ll notice the Severe Thunderstorm Warning (yellow polygon), and the Flash Flood Warning (green polygon) first. But a look at the areas circled in white show the bats headed out from their caves as night approaches. Central Texas is well known for being “bat-friendly” with the Hill Country caves providing a suitable habitat for the bats.

Jim Purpura
Certified Consulting Meteorologist
Director, Weather Forecasting