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Really wrong wind forecast

Peter,

does your flightplanner download winds or do you have to enter them manually?

I find charts are far too inaccurate for this and also the digital data provided by most flightplanners today have a lot more wind layers. A difference like this is quite out of the ordinary in my experience. Practically however, only downloaded model data (mostly GFS but some planners also use EZMW) can provide the accuracy needed for a proper planning.

LSZH(work) LSZF (GA base), Switzerland

does your flightplanner download winds or do you have to enter them manually?

I don’t enter the winds into a flight planner. I plan flights for zero wind, and then look at the wind chart(s) and estimate the likely effect along the route.

On that flight, I didn’t get the impression that the wind speed was particularly altitude dependent – in the FL160-190 range, anyway.

Yes I agree such a variation is very unusual. First time I have ever had that.

Administrator
Shoreham EGKA, United Kingdom

For planning purposes I disregard a tailwind

Why?

I’m thinking Peter might be suggesting *Bold fuel planning, but I am sure he can answer either way. Im considering UK to Norway sometime later this year, with a possible exit point somewhere in North England. Assuming we might only have 4 hours endurance at that point, and its a 3 hour leg across the water, I would have to consider that a serious unplanned headwind might prevent me from making it to dry land. However, with a tailwind, this is less of a concern in my planning. Of course what I would personally do is route via Amsterdam / Denmark just in case that tailwind isnt there and to mitigate any risks.

Last Edited by PiperArcher at 04 Feb 14:39

Light winds are hugely unreliable to forecast, because they are mathematically equivalent to the small difference between two large numbers – which way a high pressure airmass is going to move is hard to work out. So a 10kt tailwind (which at FL180 is very light wind indeed) could easily be a 10kt headwind, and now you have lost 20kt off your budget.

Anyway I think this thread is a great example why you would not want to rely on a tailwind to get you somewhere with the expected reserves

Last Edited by Peter at 04 Feb 16:48
Administrator
Shoreham EGKA, United Kingdom

Yes but we aren’t really taking about overwater legs. Nothing wrong with going up, seeing what it is like and landing for fuel if the tailwind doesn’t eventuate. Even with the UK to Norway scenario, if the winds don’t work have a clear PNR and turn around well before that should the winds not be clearly favourable.

Last Edited by JasonC at 04 Feb 21:11
EGTK Oxford

Peter,

I plan flights for zero wind, and then look at the wind chart(s) and estimate the likely effect along the route.

I see. Well, I’d have to say that I look at wind charts primarily to confirm what i see on the wind corrected operational flight plan, which comes from either of the flight planning systems I use. All of them use GFS grib data, which btw are also used by the airlines for flight planning. In my time as a dispatcher for a major carrier I must say I learnt to rely on these data pretty strongly. If they can get an airliner from a to b with 3-4 minutes and minimal fuel differences, I don’t see why not to.

Consequently, when I evaluate a new planning tool, I first look at what data it uses and if it is GFS-GRIB (which accounts for 90% of them, because the data is free) I will use it at face value. So far, I have not really seen huge variations. I usually crosscheck Pocket FMS’s fuel and time planning with my own program.

The problem with the wind charts is that they are way too inprecise in terms of resolution for a lot of weather situations, where winds vary greatly between two of the shown grid points. That way, I can well imagine such discrepancies.

One great site for a bit more precise charts is this one here:
Wetter Online Profikarten

This site not only has a pretty good resolution, it also allows checking out different flight levels 50/100/180 just to start with. In terms of free sites, it is one of the best meteorological workstations I know. You can change the chart sector from western europe to central or southern Europe as you please and also have a pretty dense time resolution. Some of the other models than GFS need registration however.

the other site which has really good stuff for aviation is flugwetter.de, which is a paid site by the German DWD. I practically do all my aviation related off duty things with it and it mostly can deliver about as much information as the much fancier workstations we use at work. I’d say it is well worth the money.

Last Edited by Mooney_Driver at 04 Feb 23:12
LSZH(work) LSZF (GA base), Switzerland

I regularly check wind forecasts vs actual and most of the time GFS is pretty good. Occasionally you get a day where it is significantly wrong, but that is rare. When I say GFS is accurate the wind speed is usually within 10 knots of planned and coming from the right general direction. The biggest inaccuracy is when a frontal system or significant wind change is expected on the route. That can be 50 miles wrong but it does come.

Planning a long over water leg is different in that I would be reluctant to go if I could only get there with reserves if the tailwind was right. In that case I would confirm I could make it zero wind and see the tail wind as contributing to my reserves.

Last Edited by JasonC at 05 Feb 08:24
EGTK Oxford

Jason

GFS is fine 99% of the time, but it is the resolution of the charts which is a problem, especcially if there are frontal systems or other convergence zones.

If you have a route from the UK to Croatia and only have 2-3 wind arrows along the route, that is totally insufficient to get the picture. In between those you can have significant deviations. That is why digital wind data are a very different story. The GFS data are available for free, which is why a lot of people use it in their products.

Trouble is, some products like Pocket FMS only use lower layers (up to FL85 in that case) which is insufficient for alpine flights (where I’d suggest to get at least layers up to FL180). Normally, these products use all available layers or at least the standard layers FL050/100/180/240 e.t.c. That is why I recalculate PFMS flight logs using another IFR product.

If pilots want to use paper charts, they have to see for such charts which have a much higher resolution than the one displayed earler in this thread.

Last Edited by Mooney_Driver at 05 Feb 13:19
LSZH(work) LSZF (GA base), Switzerland

Flitestar can correct for winds and I think the wind data is free so I might try that. However the aircraft model is well off reality and any attempt to edit it results in a crash at startup.

Administrator
Shoreham EGKA, United Kingdom

Just like Urs, for flights in central Europe, I use the winds charts of the DWD.

That grid of wind barbs on the chart you posted is just insufficien; it covers more than entire Europe…
Anybody know if there are there any charts like this one for the more peripherical parts of Europe?

Mainz (EDFZ) & Egelsbach (EDFE), Germany
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