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Cloud Highways | Cloud Streets Explained

Cloud streets, what causes these funky cloud highways?


Tyler Hamilton
Meteorologist

Tuesday, December 4, 2018, 6:44 PM - This is something you don't see everyday. How can a cloud formation create such a perfectly uniform row-like structure? The answer can be appropriately explained with a little help from some science, as we attempt to describe this relatively poorly understood feature.

  • Monday provided optimal viewing conditions in Washington State for these features, as captured by NASA satellites (image below)
  • Often confused and mistaken for gravity waves, which form from a completely different process


A National Weather Service office, located in Seattle, sent out an intriguing tweet on Monday, outlining the cloud streets as seen on satellite imagery...



NASA IMAGERY:

The Chehalis River Gap southwest of Olympia mirrors the Chehalis River, and is a relatively lower elevation area straddled by the Olympic Mountains to the north and the Willipa Hills to the south. On the continent, relatively higher pressure was located inland, with a lower pressure signal over the open waters of the Pacific Ocean. 

But, what causes these strange formations? To be blunt, we can't precisely know their exact cause – but there are a couple theories.

  • Cloud streets are always aligned with the wind, gravity waves are not (perpendicular to wave crest)
  • Water vapour condensation happens on the upward side of the roll, and evaporation typically happens on the downward side
  • Thought is rotation and friction is the primary cause of these weird formations 
  • A narrow part of the atmosphere allows these to form, unstable lower levels with daytime heating, but stable air aloft keeps these circulations organized

MORE WEATHER MODIFICATION...

Last week, we discussed the unusual snow activity east of Chicago, that ultimately was caused by aviation traffic. 

We have another example of artificial weather creation. 

Let's go on a journey to the bustling community of Norfolk, Nebraska. 

This time, a factory northeast of the community is the culprit. If you're interested here are a couple more details of the event that was captured on radar, this video will hopefully supply them:



GRAVITY WAVES, EXPLAINED, THE DISTANT COUSIN OF THE CLOUD STREET:



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