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 Unfortunately,
I must tell folks that most of the time, what they’re observing is
all in the eyes of the beholder. If it were true from every location
I have gotten this question, most people would see very few storms
pass over!
It’s a matter of distance
Think of looking at a road that goes off in the distance. Does it
appear to stay the same width? No, it appears to get narrower and
come to a point. The same observations would be taking place with
storms. The storms are separated, but that cannot be seen off in the
distance. As the storms approach, the separation becomes visible,
and the full separation is observed when the storms are close. As
they pass by, they will appear to close together again the farther
they move away.
The same occurs for radar
The farther the radar goes out, the less distinct the resolution.
This next part comes from NOAA:
The radar beam spreads out approximately 1,000 feet for every 10
miles of travel, so at 120 miles from the radar, the beam is over 2
miles wide. This spreading of the beam impacts the resolution of the
returned data. Small storm scale features that are easily seen close
to the radar are often masked at long distances. This effect is also
why “solid” lines of storms may appear to break up as they get
closer to the radar. In reality, the line of storms may have never
been continuous, but the radar was unable to resolve the gaps in the
line. [to top of second
column] |
Do storms ever really split?
Having said all this, in a few cases, storms do split. This will
happen when the wind direction changes with height. The top of a
thunderstorm will move with the upper air winds, while the lower
part will be pushed by lower-level winds. This causes what is
known as a left mover and a right mover. The left mover is
usually moving northward, and it will weaken, while the right
mover moves southerly and will strengthen. Remember that the
split was caused by winds thousands of feet up and not by ground
geography. Both storms begin to rotate when splitting, making
them supercells. Also, once they split, they don’t come back
together.
Bringing it all together
The main takeaways are that storms don’t split very often, and
when they do, it’s not because of anything present on the very
flat ground of the Midwest. That doesn’t take anything away from
your area being special! Now, I’ve got to split.
[SOURCE: Duane Friend, University of
Illinois Extension, State Master Naturalist and Climate Change
Specialist]
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