As I understand it contrails last longer in the sky when the weather is moist and rising, with the arrival of a storm in a day or two. When the weather is dry and sinking and fair weather is set to continue contrails are short and fade quicker. Does anyone have any thoughts / further info on this.
I think, what you wrote, sums it up fairly accurately.
I stand to be corrected by the more knowledgable but I think, what you need is a weakening surface high pressure area at your location and an approaching disturbance of some kind. Which is, what you said already.
This weather situation makes sure that the lower and middle atmosphere is still dry and transparent, so you can observe the contrails at all. But you need the large scale atmospheric lifting and moist air moving in at high levels, so there is enough humidity at high levels and contrails can form at all.
I think this should be the case far ahead of an approaching typical warmfront. They are marked on a surface chart (see below) as lines with breast shaped icons on them.With a warmfront normally moist air moves in at high levels first. Lots of cirrus veils will be visible along with contrails, but soon the high level clouds will increase and blot out the contrails. Then medium level clouds arrive and soon it will start to rain.
I'd also expect contrails near trough lines. This kind of disturbance means, that atmospheric lifting (caused by the high level wind current) triggers thunderstorms in an unstable airmass without an airmass change.
The UK surface charts (see link below) mark them as lines without symbols on them.
An approaching coldfront (lines adorned with triangles on the surface chart) may also yield opportunities, as there is often fair weather ahead of the front.
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The following requires that you have a fast internet connection ...
To get an overview of the next 7 days try the
surface charts from the UK Met Office (assuming you want to film in the UK)
To see what is going on, try the
high resolution satellite pictures They are wonderful. You need to select images from the UK by looking at the previews or look for UK in the file name below the previews.
Sometimes you can detect areas with contrails on those images.
Lots has been said about atmospheric soundings by other posters. You can easily view current atmospheric soundings at this link:
European vertical soundings
Select a profile near your location by clicking on the green symbol.
Ignore all the stuff on the right of the plot and just have a look at the plotted diagram. Enlarge it by clicking on it.
You see a red line depicting the temperature against altitude. Altitude is given in meters to the right and in mb to the left of the diagram. You see a light blue line which is depicting the dew point, i.e. humidity. The closer together the lines are, the moister is the atmosphere. You need these two lines to be far apart below 400 mb (see left vertical axis) and close together at levels above 400 mb.
Again this is an oversimplication but maybe useful.
Maybe you might even try to make sense from the upper level charts given
here:
In the first line marked
SLP, H500, T500 you get a certain type of forecast chart in 6 h intervals. You see the surface pressure lines known to you from surface charts. You also see areas painted in different colours which outline the airflow at roughly 5.5 km altitude. Precisely the colours indicate the altitude of the 500 mB (=hPa) layer, but well ..
Like at the surface the airflow aloft is clockwise around highs and counterclockwise around lows for the Northern Hemisphere. The airflow is parallel to the lines that divide the various coloured areas and the closer these lines are, the stronger is the wind.
On this chart you can recognize patterns which look like the letter U (upper troughs) and patterns that look like a hump (upper ridges).
Speaking very general, if you cut both patterns in half along their (mostly north south) symmetry axis, then the upstream (often western, left) half of the 'hump' and the downstream (often eastern or right) half of the trough will enhance contrails, because there is atmospheric lifting present.
This is just an oversimplification but maybe it helps.
Apart from this you can use aforesaid link to check for precipitation and medium level clouds in order to rule out periods with downright bad weather ..
Finally here is a link to the UK Met office in case you decide to ask for a
specialised briefing from an aviation met officer It's not cheap though.
good luck