I don't have an "official" explanation for you, mostly because I don't know what that means. However I can explain the science behind what you are observing.
It's caused by changing atmospheric moisture content as the plane flies. The atmosphere is non homogenous, and sometimes you have small pockets of more moist/dry air. When the plane passes through an especially dry patch the conetrail may cease as the conditions are not correct for cloud formation.
Doing a cursory google search to find you additional links for reference. Hold on will edit.
It could be a number of things, but the persistent nature indicates it is something in addition to just water vapor.
I see this frequently in my area. Contrails are typically only about 30 plane lengths and this appears much longer. hmm
And the clean break near the bottom indicates some change at that point. What exactly that change is, I'm not sure.
Vapor trail from a plane?
Why the break in the trail?
I don't have an "official" explanation for you, mostly because I don't know what that means. However I can explain the science behind what you are observing.
It's caused by changing atmospheric moisture content as the plane flies. The atmosphere is non homogenous, and sometimes you have small pockets of more moist/dry air. When the plane passes through an especially dry patch the conetrail may cease as the conditions are not correct for cloud formation.
Doing a cursory google search to find you additional links for reference. Hold on will edit.
Edit:
http://contrailscience.com/broken-contrails/
I followed that link, it doesn't look credible to me. I guess we will find out in the future.
I didn't write what I said based on that link. I suppose I am not credible either, believe what ever stupid shit you want.
Please remove the science tag from your post.
Why are you getting so upset? People usually act that way when they don't really know what they're talking about. You know, defense mechanisms.