Deciphering wind speeds from isobars

[RyanB]

Quick question—

As we know, the relationship between the spacing of isobars and wind speed, is that the closer the isobars are, the stronger the wind speeds will be. When the isobars are closer together, then the pressure changes at a greater rate over distance and the wind flows parallel in the direction of the isobar.

With that being said, is there a way to decipher what the wind speeds are likely to be, just based on looking at the spacing of isobars?

For example: if the isobars are spaced out about 150nm apart from each other, what would that tell us about the wind speed at the surface or even the winds aloft?

Here is the example for reference to this question. I would say I am only interested in the interpretation from the southeast region, but as we know the states included in the SE is up for much debate here on POA, so I’ll clarify and say just for Tennessee.

Gracias!

 

[overdrive148]

I have no idea but whatever the answer you can use Windy.com to verify!

 

[RyanB]

I have no idea but whatever the answer you can use Windy.com to verify!

I always forget about that resource. Thank you!

 

[overdrive148]

Also if it's any consolation google makes it sound surprisingly complicated:

http://www.oceannavigator.com/January-February-2003/Using-isobars-to-calculate-wind-speed/

 

[RyanB]

Also if it's any consolation google makes it sound surprisingly complicated:

http://www.oceannavigator.com/January-February-2003/Using-isobars-to-calculate-wind-speed/

Yeah, I saw that as well. Too complicated to be useful. I was just curious if there was a rule of thumb of some kind that can be used.

Ex. 200nm spacing = ~15kt surface winds etc.

Of course it’s all just guestimation like the rest of forecasting metrics.

 

[GRG55]

Okay, it's already post #6 and we are overdue for thread drift.

So, ah, I think its debatable that Tennessee is part of the SE.
Thoughts?

 

[CC268]

Dude are you kidding me? This is in the AIM, didn’t you read the AIM? Now let me get all bent out of shape as I proceed to berate you for not knowing this already.


Just kiddingggg! But I don’t know the answer to this sorry

 

[DanWilkins]

There are surface maps showing isobars, winds, fronts, etc.. readily available on the internet. Just spend some time looking at one and you'll get a feel for the wind speed-isobar spacing ratio.

 

[jaybee]

 

[NoHeat]

That's good.

What I got out of it is that you can convert the isobar spacing to wind speed not with a single handy conversion factor, but by with a slightly greater effort by reading a "geostrophic wind scale" like this:

where you read this by choosing your latitude on the y axis, then choosing your isobar spacing on the x axis, and finally by reading out the wind speed as the contour value.

It seems that this "geostrophic wind scale" must be drawn specifically to accompany your isobar chart, because the x-axis scale is peculiar to your isobar chart. But it doesn't accompany the prog charts we pilots usually see -- so we're unable to do this conversion?

 

[jaybee]

I don't know. I thought it was an interesting question and that was the first thing that came up in Google.

I just joined the 159 Weather Flight with the Florida Air Guard - I hadn't been to retraining yet but I'll ask around the shop this weekend and see if there are any rules of thumb for this.