Estimating Wind Speed

[Tom Rankin]

I was just reading another thread where the hikers had a portable wind speed indicator. How accurate are these things?

This got me wondering if there were any reliable techniques for estimating wind speed.

I've encountered everything from dead calm to winds that I could not stand up in. I was actaully holding on to a rock while laying flat just to avoid being blown away! So how fast was that? I'm sure there are a lot of variables, such as what you are wearing, and how tall (and wide! ) you are.

Any references out there?

 

[Chip]

There's the Beaufort scale. But you have to be at the ocean or at/below tree-line to use it.

 

[spaddock]

I was just reading another thread where the hikers had a portable wind speed indicator. How accurate are these things?

I think you are referring to my recent trip report up Lafayette.

We used the Brunton Sherpa: http://www.totalcamp.com/items/brunton_sherpa_atmospheric_data_center_blue_9hmh.htm

I think this is an older model as I don't see it on their site anymore. It looks like they've replaced it with the ADC Wind, ADC Pro, and ADC Summit. We tested it on the drive down with the spedometer when the winds were calm and it seemed pretty accurate. I wouldn't launch a rocket based on the data but we found it really useful up top, otherwise we would have just been guessing.


-Shayne

 

[mavs00]

I use a KESTREL 3000. They say it's pretty accurate, but who the heck's to know exactly if it right or not. I saw the TWC guys using one during Hurricane coverage last year, so they must be descent.

I like that this unit does both wind speed and temp. It combines them for wind chill, which to be honest is the real important number this time of year.

 

[Tom Rankin]

There's the Beaufort scale. But you have to be at the ocean or at/below tree-line to use it.

Chip, so if I see large waves up in the peaks, I'll know that conditions are pretty severe!

 

[Puck]

I use a KESTREL 3000. They say it's pretty accurate, but who the heck's to know exactly if it right or not. I saw the TWC guys using one during Hurricane coverage last year, so they must be descent.

I like that this unit does both wind speed and temp. It combines them for wind chill, which to be honest is the real important number this time of year.

I did NOT need to see this...Now there is yet another piece of equipement I want. Does this thing give barometric pressure? I could convinve myself its an altimeter with some great bells and whistles.

So Mavs do you have your personal Q like kames Bond or what?

 

[mavs00]

I did NOT need to see this...Now there is yet another piece of equipement I want. Does this thing give barometric pressure? I could convinve myself its an altimeter with some great bells and whistles.

So Mavs do you have your personal Q like kames Bond or what?

If you think I'm a gadget wienie, you should see ADKatie........

Actually, if you go for the Kestrel 4000 it IS an altimeter with bells and whitles. The 3000 isn't that complex and it takes seconds to use and weighs NOTHING to carry. I alway carry it in my waist pack. I don't always remember to use it , but it almost always there.

Cool toy. I got it after guessing the winds were about 100 MPH on top of Mt. Adams (NH), only to discover I was WAY off. Washington measured 70 MPH gusts around the same time and we were likely less than that even.

 

[spaddock]

I did NOT need to see this...Now there is yet another piece of equipement I want. Does this thing give barometric pressure? I could convinve myself its an altimeter with some great bells and whistles.

Check this out: http://www.brunton.com/product.php?id=260

I mean honestly, who amung us can survive without a windchill alarm. That thing would have to ring like a foghorn to be able to hear it when it's really blowing. These gadgets are just way cool.


-Shayne

 

[Chip]

Chip, so if I see large waves up in the peaks, I'll know that conditions are pretty severe!

Well, yes. But if you're observing rolling white caps above tree-line, there's a whole other heap-o-sh@t to worry about,
so I'd just try to enjoy it.

 

[vegematic]

Cool toy. I got it after guessing the winds were about 100 MPH on top of Mt. Adams (NH), only to discover I was WAY off. Washington measured 70 MPH gusts around the same time and we were likely less than that even.

WARNING: MATH ALERT
This is not unusual to overestimate wind speed. The energy of moving matter (in this case, air) depends on the velocity of the matter squared...so if the air is moving 3 times faster, it packs 9 times more energy. What people tend to feel is the energy of the wind as it hits them. If the wind hits them "four times as hard" as it did yesterday, they think it is four times as fast, when in actuality it is only twice as fast.
MATH OVER.
-vegematic

 

[Charly]

In my professional opinion......... it was REALLY windy on Lafayette on Saturday.

 

[Tom Rankin]

This is not unusual to overestimate wind speed. The energy of moving matter (in this case, air) depends on the velocity of the matter squared...so if the air is moving 3 times faster, it packs 9 times more energy. What people tend to feel is the energy of the wind as it hits them. If the wind hits them "four times as hard" as it did yesterday, they think it is four times as fast, when in actuality it is only twice as fast.

Good point Veg! Bring on the math!

I started this thread because I frequently see quotes of wind speed, but lacking a reliable instrument, I was wondering how these estimates were made. Are there any rules of thumb people use, such as, "if it knocks you over, it's around xx", or "if it ruins your new hair-do, it's around yy" ?

 

[mudhook51]

Good point Veg! Bring on the math!

I started this thread because I frequently see quotes of wind speed, but lacking a reliable instrument, I was wondering how these estimates were made. Are there any rules of thumb people use, such as, "if it knocks you over, it's around xx", or "if it ruins your new hair-do, it's around yy" ?

Tom,I once had a flash card(long gone) given to me by a helicopter crew. It showed how to estimate wind speed with a flag. Maybe someone else knows of this method?

 

[Lawn Sale]

In my professional opinion......... it was REALLY windy on Lafayette on Saturday.

That's only because it knocked you over.

So based on the emipirical data, if it knocks Charly over while he's wearing a 30 pound pack, it's gusting just above 65 mph.

It's an interesting question. I have an old Dwyer Wind Meter I use at work to measure the lake's wind speed while I'm taking samples. It seems to work well and is nice and lightweight, but not that accurate at higher speeds.

I could go back through my old college textbooks and calculate the effect of wind speeds on a Leki pole held from the strap. The amount of deflection would be an indicator of the speed. But, there would be several variables to consider, like the distance of the Leki to the ground, the height of the pole, diameter, and weight (ie: a cheaper Wal-Mart would deflect less than a carbon pole). Still, with some number crunching, it could be done, but I haven't done anything like that in the 14 years since I left college.

 

[DougPaul]

I have heard that people start getting picked up and flown at around 80mph, if that helps...

Doug

 

[Rick]

I have heard that people start getting picked up and flown at around 80mph, if that helps...

Doug

It's been my experience that:
Stand straight up - Wind good.
Stand at Angle - Wind bad.
stand with face on ground - Wind very bad.
Sorry, I had too much coffee this morning.

 

[Grumpy]

I knew some VFTT contributors had posted their observations about wind speeds and how they affect hikers a while back, and after a bit of searching around in my files came up with this:

"Winds in the 40 mph range can stagger an adult but shouldn't knock you down; the 50 mph range can knock an adult down; the 60 mph range can reduce you to crawling to make progress; the 70 mph range can pin you down, making progress very difficult."

and this:

"Buffeting you around a bit - 35-40 mph; Beginning to knock you off your feet - 45-50 mph; Knocking you down occasionally - 55-60+; Damn near impossible to walk - over 60 mph. A lower speed wind, (i.e. 30 mph) with occasional gusts to 50 is tougher to walk in that a steady 40 mph wind."

Apologies for not being able to identify who provided those excellent comments a couple years ago.

G.

 

[Tom Rankin]

I knew some VFTT contributors had posted their observations about wind speeds and how they affect hikers a while back ...

Thanks, that helps!