"Stange" Clouds Sighted Over Western Washington

Updated at 11:30 AM!

So far tonight I have gotten nearly a dozen emails with pictures of "strange triangular clouds" and a request to explain them.   Let's see what I can do.

Here are some samples, the first sent by Eric Berman and the second by Jacob Bruce.  Pretty amazing pictures.

This a line of cirrus clouds that were precipitating ice crystals.  These appendages with falling ice crystals are known as fall streaks or mare's tails.

To get a better perspective, here is a close up view of a NOAA weather satellite image at 7 PM.   You can see a line of clouds stretching east-west.  That is what folks were viewing.

It turns out that the line was there for hours and extended out over the ocean earlier.  Not chemtrails or aliens.

The high-resolution WRF model run at the UW had put a cloud line across the region at about the same time.  To illustrate, here is a 15h forecast from the 4/3 km domain for 8 PM that is simulating what a infrared satellite would see.  Not perfect, but the model wants to create a thin line of cloud across the region.

But why?   Here is are the simulated winds at 300 hPa (around 30000 ft) from the same model (again for 8 PM).  There is a big change in wind direction in that area from northwesterly winds on the north side and easterly winds to the south, a situation that can produce an areas of rising motion at the interface.

 
Looking at the UW weathercam, it does appear that these features developed in jet contrails.
A picture immediately before the clouds developed, did show some features that looked like contrails aloft.  These are oriented north-south.

 Then a cloud line developed and did look like a contrail.  But unlike typical contrails, small cumuloform elements started to form

 The elements were maintained and increased in size.

 A second line then developed (again another contrail), with similar small cumulus development.

 Then this line started to precipitate ice crystals, giving the structure than many of you noted.

So we had an area aloft that was near saturation and the moisture from the jet engines pushed it over to saturation...giving a contrail.  The atmosphere aloft was close enough to instability that small cirrocumulus elements developed and subsequently precipitated.

On the meteorological Richter scale this might be a 1, but it is an interesting diversion on the beautiful summer night.

Photo sent by Linda Thomas