Weather Blog: Can tornadoes occur without warning?
The simple answer to the question posed in this blog headline is yes. The details are a little more complicated.
My Facebook and Twitter pages were lighting up on Monday afternoon from folks who saw what looked like funnel clouds. York County schools even initiated their tornado safety procedures as a precaution. (A wise move, I think.) It’s very difficult to accurately identify a funnel cloud or a developing tornado from a still picture.
In fact, there are dozens of cloud formations that look like tornadoes, but aren’t. Click here to see an entire web page devoted to tornado look-alikes. And the National Weather Service believes that folks saw what’s called a roll cloud. These are often mistaken for developing tornadoes.
But later in the afternoon, we received several videos from folks in Newport News showing what I believe were likely weak tornadoes either trying to form or touching down. They only lasted seconds, if that.
And later on Monday evening, a high school friend sent me this picture of a water spout on the York River. More evidence that this line was capable of producing low-level rotation.
While forecasters have been getting much better at providing ample warning during big tornado outbreaks, tornadoes can and do occur without ever prompting a warning from the National Weather Service. In fact, quite a few tornadoes slip through the cracks.
A study published in the Journal of the American Meteorological Society in 2010 found that a quarter of all tornadoes never prompt a warning from the National Weather Service. Most of these are weak tornadoes, on the lower end of the intensity scale. And most are solitary tornadoes, meaning they were not part of an organized line of tornado-producing storms. Even so, the study found that 11% of all tornado deaths are caused by non-warned tornadoes. Click here to view the study.
Bottom line: tornado forecasting is getting better all the time, but it’s certainly not perfect. Sometimes tornadoes do occur without warning.