Does anyone use jet stream forecasts (such as this or this) to plan the launch date of their high altitude balloon, in order to minimize the horizontal distance travelled by the balloon?
As is well known, the jet stream is a fast-moving, high-altitude band of air traveling around the globe at a height of 9–12 km for the polar jet stream, and 10–16 km for the subtropical jet stream. The polar jet typically travels at speeds in excess of 100 miles per hour (160 km/h); though its speed depends on the time of the year: in winter it is faster, and can reach up to 300 miles per hour.
The jet stream snakes across the globe via a constantly varying path; in the UK where I am based, on the majority of days the polar jet stream is found overhead the UK; but sometimes it moves north or south for a day or two, and on such days you find no jet stream directly overhead the British Isles.
You can see historical weather maps of the jet stream here.
Using balloon flight predictors (such as this or this), I notice (unsurprisingly) that on days the jet stream is overhead in the UK, a 600 gram helium balloon is predicted to travel a horizontal distance in the order of 100 miles, from take off point to landing location. But if you run the balloon flight predictor on a day when the jet stream is not overhead in the UK, then the horizontal distance travelled is typically in the order of 10 miles.
So from the point of view of easier balloon retrieval, you are better off launching on days when the jet stream is not overhead.
However, since jet stream forecasts typically only provide data for 2 weeks in advance (and I am not sure how reliable these are over 2 weeks), and since in the UK the Civil Aviation Authority (CAA) requires a minimum of 28 days notice for a balloon flight, it's not clear if there is any way to use jet stream forecasts to find a jet stream-free day for your launch.
If you could launch on any day you choose without needing to provide the CAA with 28 days advanced notice, then it would be easy to wait for a day when the jet stream is not overhead the UK. I read that the CAA will allow some flexibility of launch date, and allow you a launch window of a few days; but you would really need a launch window of around a week or two, to stand a reasonable chance of finding a day when the jet stream is not directly overhead in the UK. More often than not you find the jet stream is overhead in the UK.
Does anyone know if the CAA might allow a more flexible launch window of around a week or two?
I believe in the US, no prior notifications to the Federal Aviation Administration are required, so in the US you can launch on any day you please. Thus in the US, checking the jet stream forecasts for a jet stream-free day would seem to be a good approach to minimizing horizontal balloon travel.