A Weirdly Perfect Cloud Curve Appeared Over The U.S.

The cirrus arc, as seen by satellite on November 28, 2019. (Image: Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview)

A spectacular cirrus arc, which stretched from Nebraska to northern Minnesota and Canada, foreshadowed the recent winter storms in the Midwest and New England.

This cirrus arc was imaged on November 28 by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, according to the NASA Earth Observatory. A meteorological phenomenon known as jet streaks, which move within jet streams, caused the incredible feature.

Jet streams are narrow, fast-flowing air currents in the atmosphere, typically at heights reaching 10 kilometres. They form alongside air masses with starkly contrasting air temperatures, and they’re major drivers of air masses and turbulent weather. The lesser-known jet streaks form a portion of the overall jet streams and exhibit winds that tend to be much stronger. These pockets of fast-moving winds play an active role in generating winter storms by pushing air farther upwards, facilitating cloud formation and precipitation.

Annotated image showing the cirrus arc. (Image: Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview)

Jet streaks aren’t normally visible, but their presence can be manifested in ways that are very obvious, such as this recently photographed cirrus arc. This particular band started in Nebraska and extended over Lake Superior. The arc is remarkable both for its size and its strangely perfect shape.

The entrance to the jet streak was near Nebraska. At this location, warm air was being pulled into the current, while at the other end, the cooler air was sinking down. The cirrus clouds formed as the air got lifted higher.

“There was just enough moisture and upward motion to create localised cirrus clouds [along the northern arc] of the jet stream,” Emily Berndt, a scientist at the Short-term Prediction Research and Transition Centre, explained in NASA’s press release.

At the time this photo was taken, a winter storm was brewing to the east, and it turned out to be a relatively big one, dropping 30 centimetres of snow in some places. And indeed, winter has started strong in much of the U.S., with some places already receiving nearly their typical annual totals. Bundle up, folks—looks like it’s gonna be a long winter.

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