Friday, May 1, 2015

1574 Cloud Street Sunset

The sunset of Tuesday April 21st, 2015 was highlighted by southwesterly streets of stratocumulus aligned with the blustery winds. The loon platform was blown into the marsh but I was going to have to wait until the wind subsided to retrieve it. The skies would clear as the sun completed its journey beyond the horizon. We were in the warm sector of the rather large low pressure area. Colder air was on the way. People were getting tired of winter...
The accompanying graphic describes the meteorology of parallel streets of stratocumulus clouds in an unstable planetary boundary level. It also explains why the bands get further apart and weaken due to friction as the sun sets and the daytime heating instability dissipates. Think of the circulations as three dimensional helical coils ( a slinky) with the updraft branch supporting the formation of the cloud and the downdraft branch enforcing the clear skies in between the cloud streets. The slinky comparison is actually quite appropriate.

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