For planning purposes, my math is a little bit different. I look at: a) what's the wind now? b) how's that compared to what it is/was supposed to be? c) what's it predicted to be? So if it's pretty calm, and supposed to be calm, and not supposed to get much worse, than fine. If it's not great, but supposed to be not great, and supposed to be better, then probably. If it's not great, and either was supposed to be good and isn't or is supposed to get worse, then probably not. I don't fly for a living, I have some crosswind experience, and I'm a bit of a baby. I don't want to get stuck in something that I should have avoided, and then later have to explain why my crappy judgement led to a bent airplane.
For wind, I don't care much about winds aloft, unless it's going to give me a 30-40k ground speed, then maybe it's silly. Wind sheer or difference between ground and low altitude? Not a fan over over 20k, but I'm a bit of a baby.
For a light crosswind, I'll usually just slip, because it's maybe a little bit easier and I don't mind slips. But for more than a little bit I'll just fly an angle into the wind on the way down, wings level. I don't know what the crosswind component is, but to me up to maybe off 30 degrees from straight isn't unusual. That way I don't have to worry about running out of rudder and it's way more comfortable for me in gusts. Just keep tracking straight. A few feet up, swing it around and slip as required.
Hi Tom, as I mentioned before wind forecasts are pretty much useless IMO. I still check them, but I take them with a grain of salt. AWOS, metars and ATIS on the other hand are better, far from perfect, but better. Foreflight is nice if you are connected to ads-b weather, you can get fairly recent winds and, at least on the plan I have, you can go into the airport tab, click on runway, and it will give you the wind split into head wind and cross wind. Once again, this can change by the minute, but it gives you a good idea of what to expect.
Beyond that, what I will do is listen to the Awos, atis, etc, get the current wind on the way in. Then I will calculate the crosswind component. For our PPL test we need to use a wiz wheel or some type of calculator and get an answer to the tenth of a mph. In reality that type of accuracy is never necessary, as the wind can change from second to second. As I gain experience I actually think that how that is taught does pilots a disservice. I find that an approximation however is very useful. The x-wind component is a simple trig calculation.
Bear with me here, without getting into too much detail, because it really doesn't matter, the crosswind component is the Sine of the difference between the runway heading and the wind direction. Now that sounds a little complicated, but it isn't. I'll calculate it out once here to show you how it works, but in the end you just need to memorize 3 or 4 numbers and you will have as accurate an estimate of crosswind as you will ever need in your flying.
Let's say I want to land on runway 05 and the wind is blowing at 10 knots from 080. To calculate the crosswind component I find the difference between the runway direction and wind direction, in this case 050 and 080. So that is 30 degrees. My xwind component = 10kts * sin30 = 10 * 0.5 = 5 knots. The crosswind in this case is 5 knots. That's how it is calculated, as you probably know.
I don't do this calculation. Instead I've memorized the crosswind multiplier for several wind angles. The ones I use are sin15 = 0.25 sin30= 0.5 sin45= 0.7 and sin 60 = 0.9 .
So for the following wind angles I use the following multipliers:
15 degrees = 0.25
30 degrees = 0.5
45 degrees = 0.7
60 degrees = 0.9
90 degrees = 1.0
That's what sticks in my head. So if I want to land on runway 12 and the wind 180 at 20 knots, I find the difference between the wind and the runway, in this case it's 60 degrees, then I multiply the wind times the 60 degree multiplier above, 20 * 0.9 = 18 knots. I would prepare mentally for ABOUT an 18 knot crosswind. Remember, the wind is almost always changing, so close enough is good enough in this case as far as I'm concerned. I'll do a couple more:
rwy 23 wind 260 at 15 260-230 = 30 so I get 15mph * 0.5 = 7.5 knot crosswind.
Rwy 33 wind 010 at 10 (360-330) +10= 40 so I get 10 mph * 0.7 = 7 knot crosswind. Remember, we don't need to be perfect, just close.
Now the pedantic and ocd amongst will point out the inaccuracy of what I do here, but since these numbers all vary anyway, they are close enough.
So memorize those 5 angles and the associated crosswind multiplier and you will quickly have a good idea of what you will see when you are close to the ground.