DALLAS — The early-morning storms that rolled through North Texas on Wednesday mostly weren't severe.
But that wasn't the case, if only briefly, in Rockwall County, where the leading edge of the storms produced an EF-1 tornado that damaged about five homes in the Bluebonnet Ranch neighborhood.
The official designation of a tornado by the National Weather Service might have come as a surprise to many North Texans. Our area was under a tornado watch for most of the morning, but no tornado warnings were issued.
Here's why.
Wednesday morning's tornado was small, and brief, and that's partly why it did not show up on radar and did not trigger a tornado warning.
The tornado produced peak winds of 100 mph, was about 50 yards wide and its path only lasted half of a mile.
The spin-up was an example of one limitation of doppler radar, which tracks storms by using a radar beam from a site south of Fort Worth. While the radar tracks the weather in real-time, it still can take a few minutes to make a complete scan of the atmosphere.
The tornado in Rockwall County on Wednesday morning lasted only about two minutes, from 4:34 a.m. to 4:36 a.m.
Additionally, the storm was about 55-60 miles from the radar site. And when the radar beam scans the atmosphere, the beam hits a storm at about 7,500 feet into the atmosphere.
In Wednesday's storm, this beam would have been too high to detect low-level rotation like we saw in Rockwall County.
All of those factors can result in what happened Wednesday morning, with a brief spin-up going undetected between radar scans.