Why only one contrail today?

[steve holmes]

I was outside most of the day and the only contrail that I saw was this one that I saw at 3:12 pm. It was heading eastward, a bit east of where I was, which was 13 miles east of Sacramento.
The lack of contrails would mean dry air. If the trail was in pieces, it would indicate the plane went through places where there was not enough and enough humidity for contrails to show up. With this plane, the trail was constant from horizon to horizon. I looked on FR24 for other planes at the same altitude, which ought to have been seen similarly but none of the ones at the same altitude near this one were visible.

 

[deirdre]

I looked on FR24 for other planes at the same altitude, which ought to have been seen similarly but none of the ones at the same altitude near this one were visible.

can you grab a screen shot of that? of fr24 and the other planes around. and name the plane you think you are seeing? ( i looked but i think im messing up my utc conversion)

Spoiler

this is my guess.. just so the guys can tell me if i got it right - i'm still learning too

you saw as520 at 39,000 feet but the only other plane that goes through that patch of sky at 39,000 feet , within 45 minutes anyway) was a cl-60. which looks like a much smaller plane.

so my guess is that the cl-60 engines didnt produce as much water for the conTAIL (it wasnt persistent) or the contail you saw was aerodynamic, which the cl-60 couldnt pull off cause its wings are small. probably the engine thing.

 

[SR1419]

the trail was constant from horizon to horizon

It doesnt look that way from the picture. It looks like the trail dissipates.

 

[Dan Page]

Using FR24 playback, I found 2 possibilities, KLM282 a B787 and UAL990, also a B787, both enroute from San Francisco to Europe and both still climbing, which means they were using climb power and they were also near their gross weight due to the amount of fuel they would have on board. 3:12 PM on the west coast is 2312z. Both planes were basically on the same course and heading northeast, not east, but these were the only two aircraft that were anywhere near the location at that time. They were both relatively low for contrail formation, around 30000 ft, but the air up higher is much dryer, so as they climbed their contrails would probably have ceased. As it was, the contrail was fairly short and dissipated quickly.

 

[deirdre]

heading northeast,

based on the shadows of the second pic i think the plane is flying (pretty much due) south ?

 

[Dan Page]

based on the shadows of the second pic i think the plane is flying (pretty much due) south ?

You're right, it kind of does, but with such a short trail and so far away, it is really hard to say, maybe it was ASA434 enroute to LAX, it was traveling straight south.

 

[Trailspotter]

I suspect that the @steve holmes' camera clock is still set to PDT and the time of the photo actually was about 22:12 UTC. Unlike one hour later, there was a good candidate flight at the time. The Korean Air Boeing 777 (flight KAL5) was heading to Las Vegas at 37,000 ft:


It was flying higher than other planes in the same area at about the same time. The ambient temperature at this altitude was lower, therefore water vapour from the plane engines' exhaust was more likely to condense upon mixing with the surrounding cold air despite a low relative humidity of the latter. This would explain why there was a short contrail behind this plane, while the other, lower flying planes were trail-less.

I have attached the kml file of KAL5 track from FlightAware. When seen from the (approximate) locations of photos at and near a cycle bridge (38°35'32.00"N 121°19'52.59"W), it matches photos very well:


PS
I have identified the exact location of the second photo (38.587719243° -121.334608250°) and added it to Google Earth. The contrail matches the KAL5 track perfectly with the plane location corresponding to 22:10 UTC:

 

[deirdre]

@steve holmes also , from now on you are going to need to provide better data if you post any more contrail pictures. You have been here long enough to know what kind of data the guys need.

If it is 3:12 according to your camera time, then state that. If it is actually 3:12 according to your watch then state that. If you claim "other planes around the plane" then give us the plane ID of what plane you are looking at, or think you are looking at.

If you used the fr24 app and pointed it at the plane to get the ID state that. (so we know right off the bat you got the right plane, time and direction).

Also give us GPS or a verbal location (except if you are at home obviously) that is more specific, so the guys dont have to waste time figuring out where you are at.

 

[steve holmes]

You're right. My camera didn't "fall back". Thanks for the inf

I suspect that the @steve holmes' camera clock is still set to PDT and the time of the photo actually was about 22:12 UTC. Unlike one hour later, there was a good candidate flight at the time. The Korean Air Boeing 777 (flight KAL5) was heading to Las Vegas at 37,000 ft:


It was flying higher than other planes in the same area at about the same time. The ambient temperature at this altitude was lower, therefore water vapour from the plane engines' exhaust was more likely to condense upon mixing with the surrounding cold air despite a low relative humidity of the latter. This would explain why there was a short contrail behind this plane, while the other, lower flying planes were trail-less.

I have attached the kml file of KAL5 track from FlightAware. When seen from the (approximate) locations of photos at and near a cycle bridge (38°35'32.00"N 121°19'52.59"W), it matches photos very well:


PS
I have identified the exact location of the second photo (38.587719243° -121.334608250°) and added it to Google Earth. The contrail matches the KAL5 track perfectly with the plane location corresponding to 22:10 UTC:

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