Scattered showers have been common this summer and we're not talking about individual bathing habits.
Plenty of farmers have been singing the spotty shower blues. It stirs a glimmer of hope when you see a wall of rain in the distance and causes disappointment when the dark cloud passes over with nary a drop. What the heck... did that farmer that got lucky mow hay or wash his pickup?
That over yonder phenomenon where you can see the rain is called a "rain shaft," according to DTN ag meteorologist John Baranick. And, you can gather a few cloudy clues from looking at those walls of water from afar -- even if they aren't delivering the widespread precipitation you desire.
"It's interesting to look to see where the rain is actually coming from," Baranick said. "If it's coming directly below the highest part of the cloud, the shower doesn't last long as the rain collapses the upward motion required to generate the rain in the first place. If it's offset by a bit, the rain can continue to fall while the cloud's upward motion produces more."
The difference between scattered pop-up showers and organized showers is largely about "focus."
"When we see pop-up showers during a summer day, it's largely because there is good heat and moisture near the surface. I like to think of a pot of boiling water as a good visual." Baranick said. "As the sun (stovetop) heats the atmosphere (pot of water), you start to see bubbles rise (like bubbly cumulus clouds forming overhead midday). When you heat up the water (atmosphere) enough to get a rapid boil (like in the afternoon), you likely get enough for rain to fall. But that's heating evenly over a large area. The bubbles are very localized and not widespread. The whole pot of water does not just magically turn to gas and jump out of your pot. There is no focus, it is seemingly random."
According to Baranick, organized events usually have a feature that is driving them, and it could be myriad things like a front, upper-level disturbance, terrain, or something else. There are lots of reasons, but these features focus the heat and moisture to a smaller area. If it is moving, like a front, then you get an organized area of widespread showers moving through.
Or think of it as the feature picking up the heat and moisture as it moves through like a push broom on your farm shop floor gathering scattered dust bunnies, concentrating them into a line of dirt. Or showers, in this analogy.
But even these features could produce spotty rain, too, right? Fronts do not always have widespread showers. We saw a lot of this across the northern tier of the country in June.
So, two main questions come into play, Baranick said. First: Is the feature strong and is it consistent? Is my push broom solid, or are there gaps in the bristles?
Secondly: Is there enough heat and moisture to produce the rain across the feature? To use the broom example, are there enough dust bunnies to collect to form a line of dirt?
"If the answer is yes to both, then you likely get a widespread event," Baranick said. "If it is 'yeah, but... ' you likely get scattered showers. If it's 'eh, maybe?' you likely get isolated showers."
Growing up, if we spotted a rain event in the distance, we would occasionally drive to see if we could find out what neighbors were "living right" (my father's term).
I still get that same urge when I hear a distant rumble. The dogs and I load up and take John Fogerty and CCR along for the ride:
"I want to know, have you ever seen the rain?
Comin' down on a sunny day."
Read John Baranick's weather blog on scattered showers: https://www.dtnpf.com/…
Can you actually smell the rain? The answer is yes and here's why:
Pamela Smith can be reached at Pamela.firstname.lastname@example.org
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