What is a cutoff low and why do they sometimes bring dangerous weather?

Whether it’s a stalled tropical system, a slow-moving thunderstorm or a stationary front; any stagnant weather pattern often turns into a dangerous situation. The same can be said about a cutoff low.

The powerful winds of the jet stream are responsible for pushing weather patterns around the world. Typically they move from west to east in a steady fashion. Every so often a low pressure system, or storm, will get pinched off from the jet stream and become stalled. This is where a cutoff low gets its name.

HOW LONG DOES THE PATTERN LAST?

A cutoff low can linger over one spot for a few days or even a week or more until something comes along to push it away. What is deceiving is that while the systems are considered stationary, they do tend to wobble around, which means the exact same weather won’t occur every single day.

Compare it to a boat that is anchored in a lake. The anchor is thrown overboard and keeps the boat generally in the same spot. However, the boat is still going to drift around a bit. The Earth’s atmosphere is essentially water, to the cutoff low does the same thing.

WHY A CUTOFF LOW IS PROBLEMATIC

Anytime a system remains stagnant you can anticipate some problems. Typically, when a cutoff low develops near our area we receive moisture off the Gulf of Mexico and Atlantic which makes the air quite tropical. During the warm season, this leads to a daily rain or storm chances and the potential for repeated downpours and flooding threat.

Flash flooding is responsible for the greatest number of weather-related fatalities in the United States. Landslides and debris flows are also possible with prolonged rainfall.

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