[Jan]

I'm stuck. Can anyone please spare a sec to point me the way:

The question:
In the northern hemisphere, in particular point of a weather system where there is geostrophic wind direction of 020° true, the centre of low pressure is:
Correct answer as per key: b.) In the direction of 290 true from that point
My answer: a.) In the direction of 110° true from that point

My line of thought was that since the wind is blowing from the direction 020° having put my back against it as Buys Ballot would, the centre of low pressure should be to my left and thus 110 true from that point.
Only way the centre of low pressure is to 290° from that point is that the wind is blowing in the direction 020° rather then from it, as one would expect with wind.

Where em I wrong?

[GolfHotel]

If the wind is at your back and your nose is pointing at 020 then 290 is on your left. Simples. Have you got left and right muddled per chance? Your were going about it the right way.

Think of it as facing North, Then the West is on your left.

[Irv Lee]

But isn't the wind FROM 020? I guess it depends on the exact wording of the question but simply saying wind 020 is from 020 normally

[GolfHotel]

I’d expect a pressure gradient force wind to be quoted as flowing from high to low. And a geostropic wind is that wind modified by the coriolis effect. Hence would expect it to be heading in the direction mentioned. In this case 020 deg.

However Irv is absolutely correct the norm is the other way around. I’ve no idea if there is a convention regarding this. It’s just the way I was taught. I’ve never noticed the apparent contradiction. Dohh.

[lobstaboy]

The op is correct.
Whoever set, checked, published etc the question is wrong.

[GolfHotel]

From BGS met course for the ATPL exams.

[PaulSS]

We can deduce from all the above that:

(a)Jan is correct, the low pressure will be 110 degrees from the person with his back to wind of 020 'cos winds are always described as being blown from and not to.

(b)Don't believe all that's written in question and answer banks.

(c)GH needs to charge his phone (I've been accused of being a 100% Charge Nazi )

[GolfHotel]

Or more accurately we can deduce:

Geostropic winds are normally given in a different way.

A quick google will quickly confirm this is accurate. (Just look at a few academic web site)

Some people can’t tell the difference between a question bank and course notes.

I’m using a tablet not a phone.

What Jan can take away is that pilots will often get stuck in when they should know better.. Assuming she is a ppl student she shouldn’t really get a question phrased like this.

[Jan]

Thanks chaps! thanks GH, Very helpful
I might be back with more

I'm indeed aspiring for PPL and I came across this in the Pooley's Air Pilots Manual. If the idea behind putting such formulated question in this beginners text book was to make me thoroughly revise all that I've learned so far and to expand my horizons past it; well played.

[GolfHotel]

LOL thats interesting to hear. Explains it all.

The lesson may be that you have to be very careful with units. Just for direction for instance you can have MH, CH, TH, Track, Course. (and thats just for going forward so ignoring radials etc.) You have to know what you're dealing with and how to get from one to the other. It is all fun at the end of the day, honest.