What “training” storms are and how they pose a risk of flash flooding
When checking the weather app during an active summer week, a simple rain icon rarely tells the whole story. If you glance at the radar and see storms lining up across Central Missouri, you might hear meteorologists using the term "training".
It is a word that frequently pops up in flash flood warnings, but what does it actually mean for your neighborhood, and why is it a primary concern for the I-70 corridor over the next few days? To understand this phenomenon, it helps to pull away from the maps and picture a set of railroad tracks.
Imagine standing at a railroad crossing. If a single train car rolls past, it clears the intersection in a matter of seconds, barely disrupting your day. But if a locomotive is pulling 50 sequential boxcars, you are going to be stuck waiting at that crossing for a significant amount of time. In the atmosphere, a training thunderstorm pattern works exactly like those boxcars.
Instead of a single storm cell moving into your area, dumping some rain, and moving out, a series of individual storm cells develops and travels over the same pieces of land, one after the other. While one cell wraps up and moves east, the next one is firing up right behind it to take its place.
Training storms do not happen by accident; they require a highly precise atmospheric setup that frequently locks in over Missouri during the late spring and summer months. First, a stationary or very slow-moving frontal boundary settles in over the region. This serves as the physical boundary or "track" where the air is forced to rise and spark storms.
For storms to clear out, high-altitude winds usually need to push them across the front. In a training setup, the winds a few miles up blow perfectly parallel to the stalled front. Instead of pushing storms off the track, the wind guides them along it.
As night falls, a river of fast-moving, incredibly humid air from the Gulf rises a few thousand feet above the surface. This low-level jet continually pumps moisture into the tail end of the line, regenerating new storm cells like an endless assembly line.
Unlike a classic severe weather squall line, training setups rarely grab headlines for 60 mph winds or destructive hail. The primary hazard here is cumulative water. When 2 to 4+ inches of rain fall over the same county in just a few short hours, the ground quickly hits its saturation point.
Over the next couple of days, this "training" setup is expected to be a concern when it comes to the potential for flash flooding in Mid-Missouri. This has triggered a flash flood watch for areas along and south of I-70, as this is where the boundary, steering upper-level winds, and moisture are expected to most likely align, causing persistent storms for some. It does not take much rain to cause water levels to rise to a point at which flooding is an issue, so if you come across a covered roadway, turn around, don't drown.
