WELD COUNTY, Colo. — The National Weather Service (NWS) now says there were at least three tornadoes in Weld County on Tuesday. They are investigating one other possible report near Keenesburg that could make four, and they said there were likely one or two in Adams County. All occurring at about the same time.
With the three confirmed in Weld County, that makes 296 since 1950. NWS says that’s more than any other county in America.
Granted Weld is one of the bigger counties in the country, but that’s still a lot of tornadoes.
The reason is a reoccurring boundary of colliding air known as the Denver Convergence and Vorticity Zone, or DCVZ.
A common storm setup brings surface winds out of the southeast that collide with air coming down off the Rocky Mountains. That creates a boundary of rotating air that develops horizontal to the ground.
Then thunderstorms form on that boundary and pull that rotating air up into the cloud, creating a tornado. In most cases, there are multiple tornadoes at the same time when they form in this manner.
That National Weather Service said Tuesday’s boundary wasn’t a classic DCVZ, but a similar boundary.
These boundaries tend to set up most frequently over Weld County. And the tornadoes that they produce are weak non-supercell tornadoes more commonly known as landspouts. Those usually cause little to no damage.
NWS said all three Weld County tornadoes from Tuesday will be rated EF-0, and so will the other one if they can confirm that it is not a duplicate report from one of the others.
They also said at least one tornado will likely be confirmed over the next couple of days. That tornado will also get an EF-0 rating if confirmed.
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