Cutoff Low, Responsible For Flooding in the Midwest and Southeast, Is Mesmerizing in Satellite Imagery

A slow-moving low pressure system known as a cutoff low, responsible for triggering significant flooding in parts of the Midwest and Southeast, has taken on a spectacular presentation in satellite and other meteorological imagery during its multi-day journey.

Satellite imagery tuned to detect water vapor in the upper-levels of the atmosphere helps meteorologists pick out subtle features that can influence weather at the ground. There was nothing subtle about this cutoff low.

It swept into the Plains and Midwest last weekend, slowed and dropped south-southeast into the mid-Mississippi Valley by Tuesday. By that time, the low wrapped dry air in its circulation and had moist air surrounding it, noted Stu Ostro, senior meteorologist The Weather Channel at and long-time weather image guru.

By Wednesday, as the low settled into the Southeast, its diameter was about 900 miles. Its moisture stretched from the coast of Virginia and North Carolina westward to Missouri and Arkansas and from Lower Michigan nearly to the Gulf Coast.

The low is expected to exit off the East Coast by Saturday, about a week after developing in the northern Plains.

(MORE: Why Weather Moves Slower This Time of Year)

Some meteorologists describe the large lows as cinnamon rolls as strips of dry air and more moist air become entwined in its circulation.

The first reply to the NOAA tweet below, also a water vapor loop but with a different table of colors, suggest it resembled the NFL's Los Angeles Rams helmet.

Before it developed, the forecast of this large low pressure gyre had the attention of meteorologists.

It's called a cutoff low because it became detached from the jet stream that would otherwise continue steering it east.

The loop below from the European forecast model over the same time period (May 16-20) shows the northward bulge in the jet stream – indicated by dark maroon colors working into the upper Midwest –almost acting like a wave splashing over the cutoff low and trapping it.

As this cutoff low was gyrating, Tropical Storm Arthur was brushing the Outer Banks of North Carolina on Monday. This fascinating combination of visible satellite imagery with lightning flashes detected by the GOES-East geostationary lightning mapper showed thunderstorms associated with both systems.

And their juxtaposition on water vapor imagery was even more fascinating Tuesday. The cutoff low resembled a black left eye, flanked by the fizzling Arthur acting like a right eye, with the two split by an elephant trunk-shaped moisture plume from the Caribbean Sea.

Given the cutoff low's slow movement, parts of the Midwest were under a blanket of clouds for several days in a row, as these high-resolution visible satellite images taken Sunday through Tuesday showed.

Slow-moving weather systems often produce prodigious precipitation, either rain or snow.

Here is a radar loop from Saturday through Wednesday, showing the progression of rain from this cutoff low.

This cutoff low triggered major flash flooding in Chicago and set May rain record there. The rain overwhelmed a pair of dams in Michigan and triggered other flooding in parts of Kentucky, Ohio, Wisconsin, the Carolinas and Virginia.

(WEATHER RECAP/FORECAST: Slow-Moving Low Brings Flooding)

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