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Weather Blog - Thunderstorm Complexes Collided Last Night

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Posted at 3:38 PM, Jun 04, 2020
and last updated 2020-06-04 16:44:50-04

Good afternoon bloggers,

Who was awake at 1:30 AM, or really from around 2 AM to 4 AM? I was, and we were monitoring colliding outflow boundaries. I was a bit surprised when it resulted in a couple of weak EF-0 tornadoes. One tracked from around Blue Springs Lake to Lake Lotawana.

What is an outflow boundary? An outflow boundary is created by thunderstorms, and usually a big complex of thunderstorms. Most thunderstorms do produce the spreading out of rain cooled air, but usually weaken fast after the thunderstorm weakens. When there are hundreds of thunderstorms organized into a big comples, known as an MCS or Mesoscale Convective System, a large area of rain cooled air will develop. When this larger area of rain cooled air develops, it will then spread out away from the thunderstorms. This outflow of cooler air forms into what seems like a weak cold front. New thunderstorms will often form near this outflow boundary.

Last night we had two organized boundaries and they collided just east of downtown KC. Take a look:

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This radar image shows the colliding boundaries north for Excelsior Springs, MO. Here is the satellite image:

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The thunderstorm complex from the northwest was seemingly weakening, but when they collided, the entire complex got energized and produced a huge MCS:

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As the boundaries collided, the air was forced to rise very fast. The resulting stronger updrafts resulted in producing the little spin-ups that likely formed into EF-0 tornadoes with winds of 60 to 85 mph. The damage was rather limited, but there was some.

It will be calmer tonight. We will be tracking some interesting developments for the weekend and next week. Tropical Storm Cristobal has weakened, but it will move back out over the warm Gulf of Mexico waters and intensify Friday and Saturday. Some models bring rain into KC from this system. I have low confidence in that at this moment.

Thank you for sharing in this weather experience. Have a great evening!

Gary