Wind shear

[Metsfan]

I found this blog post on wunderground about wind shear calculation, and I tried to get the answer that he got, but for some reason I am having difficulties.

 

http://www.wunderground.com/blog/24hourprof/comment.html?entrynum=24

 

I did this,  

 

sqrt( (40)^2 +(10)^2))=41 knots which is not the same as the what is in the posted example

 

Is the angle involved?

 

Thanks.

[Chinook]

Vector addition and subtraction will have to use the law of cosines, given the two lengths of the vectors and an angle. Wind shear is a subtraction, so

 

subtraction:

 

R= squareroot(A^2 + B^2 - 2ABcos(theta))

 

So this depends greatly on the angle theta, if A and B are close to the same length.  If one of them is zero, it doesn't depend on the angle.

 

squareroot(40^2+10^2 - 2(40)(10)cos(50)) =  34.435

[Metsfan]

Vector addition and subtraction will have to use the law of cosines, given the two lengths of the vectors and an angle. Wind shear is a subtraction, so

 

subtraction:

 

R= squareroot(A^2 + B^2 - 2ABcos(theta))

 

So this depends greatly on the angle theta, if A and B are close to the same length.  If one of them is zero, it doesn't depend on the angle.

 

squareroot(40^2+10^2 - 2(40)(10)cos(50)) =  34.435

Thanks. I have one more question. Is the bulk vector difference the same as the bulk wind difference? The vector difference I think falls under the pythagorus theorem, and the wind difference is the is just subtracting the two values, because a couple of weeks ago I asked about the brn shear, and I am still trying to mathematically grasp the concept. I looked at this webpage http://www.spc.noaa.gov/exper/soundings/help/index.html to get more info, but it doesn't seem to help. Thanks again.

[Metsfan]

Vector addition and subtraction will have to use the law of cosines, given the two lengths of the vectors and an angle. Wind shear is a subtraction, so

 

subtraction:

 

R= squareroot(A^2 + B^2 - 2ABcos(theta))

 

So this depends greatly on the angle theta, if A and B are close to the same length.  If one of them is zero, it doesn't depend on the angle.

 

squareroot(40^2+10^2 - 2(40)(10)cos(50)) =  34.435

Hi, How did this person get an angle of 50?