Large storm systems known as extratropical cyclones or winter cyclones need favorable atmospheric environments to grow in. Generally, as the environment becomes more favorable, the climate becomes stormier. However, over the North Pacific Ocean during midwinter, when the environment becomes optimal for storms, storminess actually decreases compared to the surrounding months. The cause of this decrease is not agreed upon, but a better understanding of the so-called 'midwinter minimum' may improve our understanding of how storms respond to their environment, an environment which is increasingly changing due to human-caused climate change.

In this work, we model storms like traffic density on a freeway. If the flow of traffic (input of storms) spikes without an increase in the speed limit (environmental wind speed), traffic density can increase to form traffic jams (large, stationary weather systems). However, if the flow spikes when the speed limit increases, traffic density (the size of storms) will decrease because the higher background flow rate prevents the accumulation of cars (energy). In other words, if the environmental wind speed becomes too high, storms do not spend enough time in the environment to grow large. We find evidence of this 'unjamming' mechanism in observationally derived data.