Thu Sep 17, 2020 11:48 am
#1796736
Apologies in advance if the answer to some of my questions are buried in my Met study books...also apologies if I struggle to word the question succintly...
The club I rent from have a perfectly reasonable wind gust limit of 20 knots and a x-wind gust limit of 15 knots.
When I refer to Windy.com as part of my flight planning, even on days where the wind is relatively light, the wind gusts displayed remain high and close to limits. In fact, looking ahead at the next two weeks, most of the wind gust values exceed 20 knots:
Numerous times I have looked at Windy.com, however, I have gone to the airfield and the wind has been just fine. There might be an occasional light gust, but otherwise no problem.
Now, IIRC a gust doesn't get reported unless it is 10 (?) knots higher than the base wind speed (but I may have made that up), but I've got a few questions:
1) What's the threshold for gusts to be depicted in practice, in terms of frequency?
For example, if the wind is 10knots, but there is a gust every 10 minutes that is 15 knots, I assume Windy.com will correctly show gusts of 15kts, but is very different to a situation where the wind is 10 knots, but it's gusting between 10 and 15 every few seconds.
In other words, there's a variability in wind speed that triggers the gusts to be recorded, but is there a frequency variability also?
2) What other sources do people rely on - or what additional analysis do you do - to get a better steer on wind for a flight?
If I translate all of this into a better statement: right now, let's say I want to go flying tomorrow. I look at Windy.com and it shows a wind of 11 - 13 knots straight down the runway (within limits), but wind gusts of 25 - 26 knots, which is outside limits.
Now, for all I know, that forecast might be supremely accurate and I wouldn't want to be flying with those gusts. In any event, I won't bother to contact the club to book a rental, as it's outside of my limits.
But - in practice - 'is it really outside of the limits and are those gusts accurate to rely on?', is really what I'm saying. Could the wind be 11 - 13 knots, with a few guests 15 - 20 knots (say), but a freak, infrequent gust that might be higher?
Are those gusts actually what is expected, or a potential view of what might occur worst case? Are they average projections, or maximum projections?
I am most definitely not trying to argue with Mother Nature, but equally I get the impression that I stopping myself from flying arbitrarily because of Windy.com, and my hypothesis is that Windy.com over-exaggerates the wind more often than not and is a useful guide, but is not a useful definite benchmark for whether I'm allowed to go flying...
p.s. Finally, of course I refer to the Met forms as part of my pre-flight planning, but rarely are they as pessimistic as Windy.com. But then you get into a dangerous situation where you develop a confirmation bias towards one weather source because it tells you what you want it to hear....
The club I rent from have a perfectly reasonable wind gust limit of 20 knots and a x-wind gust limit of 15 knots.
When I refer to Windy.com as part of my flight planning, even on days where the wind is relatively light, the wind gusts displayed remain high and close to limits. In fact, looking ahead at the next two weeks, most of the wind gust values exceed 20 knots:
Numerous times I have looked at Windy.com, however, I have gone to the airfield and the wind has been just fine. There might be an occasional light gust, but otherwise no problem.
Now, IIRC a gust doesn't get reported unless it is 10 (?) knots higher than the base wind speed (but I may have made that up), but I've got a few questions:
1) What's the threshold for gusts to be depicted in practice, in terms of frequency?
For example, if the wind is 10knots, but there is a gust every 10 minutes that is 15 knots, I assume Windy.com will correctly show gusts of 15kts, but is very different to a situation where the wind is 10 knots, but it's gusting between 10 and 15 every few seconds.
In other words, there's a variability in wind speed that triggers the gusts to be recorded, but is there a frequency variability also?
2) What other sources do people rely on - or what additional analysis do you do - to get a better steer on wind for a flight?
If I translate all of this into a better statement: right now, let's say I want to go flying tomorrow. I look at Windy.com and it shows a wind of 11 - 13 knots straight down the runway (within limits), but wind gusts of 25 - 26 knots, which is outside limits.
Now, for all I know, that forecast might be supremely accurate and I wouldn't want to be flying with those gusts. In any event, I won't bother to contact the club to book a rental, as it's outside of my limits.
But - in practice - 'is it really outside of the limits and are those gusts accurate to rely on?', is really what I'm saying. Could the wind be 11 - 13 knots, with a few guests 15 - 20 knots (say), but a freak, infrequent gust that might be higher?
Are those gusts actually what is expected, or a potential view of what might occur worst case? Are they average projections, or maximum projections?
I am most definitely not trying to argue with Mother Nature, but equally I get the impression that I stopping myself from flying arbitrarily because of Windy.com, and my hypothesis is that Windy.com over-exaggerates the wind more often than not and is a useful guide, but is not a useful definite benchmark for whether I'm allowed to go flying...
p.s. Finally, of course I refer to the Met forms as part of my pre-flight planning, but rarely are they as pessimistic as Windy.com. But then you get into a dangerous situation where you develop a confirmation bias towards one weather source because it tells you what you want it to hear....
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