Despite the relative humidity being 21% at 40,000ft, I got close-up footage on two sprayers leaving so-called “persistent contrails” over Chiloquin, OR, 11-8-16.
The most recent Wyoming Soundings data from 40 miles west showed it was much too dry for persistent contrails to form. You need saturated air – 100% relative humidity. Even the shills, including Mick West, admit as much (although he claims air is saturated at 67%).
Two Boeing 737s – Alaska Air & Southwest – left trails that persisted and spread in the dry air.