Range Report Judging wind speed by observing rain
- Thread starter MLC
- Start date
Re: Judging wind speed by observing rain
i've used marage in my scope but never heard of judging rain.if the rain was very heavy at all long shots would be tough regardless of wind.
i've used marage in my scope but never heard of judging rain.if the rain was very heavy at all long shots would be tough regardless of wind.
Re: Judging wind speed by observing rain
So far, so good.
Wind and rain are related, but typical weather patterns tend to put winds higher as a front moves in, then die off as it becomes settled in. I would think that if one actually went out to shoot in a significant rain event, they'd soon realize that rain's main effect is to block visibility.
I doubt rain could be an effective wind telltale.
I say this after spending a year and some in 'Nam, where the Monsoon quickly makes a believer out of one. Me; I believe I'll have another beer, and be damned glad I'm still around to enjoy one.
Greg
So far, so good.
Wind and rain are related, but typical weather patterns tend to put winds higher as a front moves in, then die off as it becomes settled in. I would think that if one actually went out to shoot in a significant rain event, they'd soon realize that rain's main effect is to block visibility.
I doubt rain could be an effective wind telltale.
I say this after spending a year and some in 'Nam, where the Monsoon quickly makes a believer out of one. Me; I believe I'll have another beer, and be damned glad I'm still around to enjoy one.
Greg
Re: Judging wind speed by observing rain
On rain effects:
http://snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=959810
(with exclusive comment by Lindy)
on rain angle related to wind speed I found this interesting article that looks at it from an engineering standpoint when designing houses.
http://www.jstage.jst.go.jp/article/jaabe/4/1/223/_pdf
Basically:
depending on rain drop size rain will fall at different rates but most of the time it is between 10-19 or so mph, 19 being a soft maximum. The guys who did that article posted above just went with a mean rain speed of 4.5 m/sec which is like 10 mph or so.
V= 4.5*I^0.107
V = mean speed of rain drops in meters/sec
I = intensity of rainfall in millimeters/hr (similar to our inches/per hour measurement)
we can change the formula they give around to be:
U = (tan 0)*4.5*I^0.107
U would be your wind speed in m/sec and 1 m/sec = ~2.24mph
So if you can get the angle of deflection of the falling drop and know roughly how fast the rain is falling you could...theoretically calculate wind speed.
good luck...I think I will just stick to watching trails and following up fast
On rain effects:
http://snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=959810
(with exclusive comment by Lindy)
on rain angle related to wind speed I found this interesting article that looks at it from an engineering standpoint when designing houses.
http://www.jstage.jst.go.jp/article/jaabe/4/1/223/_pdf
Basically:
depending on rain drop size rain will fall at different rates but most of the time it is between 10-19 or so mph, 19 being a soft maximum. The guys who did that article posted above just went with a mean rain speed of 4.5 m/sec which is like 10 mph or so.
V= 4.5*I^0.107
V = mean speed of rain drops in meters/sec
I = intensity of rainfall in millimeters/hr (similar to our inches/per hour measurement)
we can change the formula they give around to be:
U = (tan 0)*4.5*I^0.107
U would be your wind speed in m/sec and 1 m/sec = ~2.24mph
So if you can get the angle of deflection of the falling drop and know roughly how fast the rain is falling you could...theoretically calculate wind speed.
good luck...I think I will just stick to watching trails and following up fast
Re: Judging wind speed by observing rain
I supposed that could be done, but in Seattle here where it drizzles MOST of the timeand then gushes occasionally you might have your hands full.
I supposed that could be done, but in Seattle here where it drizzles MOST of the timeand then gushes occasionally you might have your hands full.
Re: Judging wind speed by observing rain
Here's some follow-up on the Jello-to-the-wall numbers:
The following table contains fall speeds based on observations by Gunn and Kinzer (1949). These data were collected under sea-level conditions (1013 millibars and 20 degrees C).
Diameter (mm) Fall speed (m/s) Diameter (mm) Fall speed (m/s)
0.1 0.27 2.6 7.57
0.2 0.72 2.8 7.82
0.3 1.17 3.0 8.06
0.4 1.62 3.2 8.26
0.5 2.06 3.4 8.44
0.6 2.47 3.6 8.60
0.7 2.87 3.8 8.72
0.8 3.27 4.0 8.83
0.9 3.67 4.2 8.92
1.0 4.03 4.4 8.98
1.2 4.64 4.6 9.03
1.4 5.17 4.8 9.07
1.6 5.65 5.0 9.09
1.8 6.09 5.2 9.12
2.0 6.49 5.4 9.14
2.2 6.90 5.6 9.16
2.4 7.27 5.8 9.17
http://www.madsci.org/posts/archives/2000-07/962626446.Ph.r.html
***
Here's what I read last night while studying something else:
http://hypertextbook.com/facts/JianHuang.shtml
On snippet in there puts the average raindrop at 25 fps, or 7.62 meters/second. According to the earlier observations at sea level, that would correspond to a drop size between 2.6 and 2.8 mm.
So, the answer all "depends"...
Here's some follow-up on the Jello-to-the-wall numbers:
The following table contains fall speeds based on observations by Gunn and Kinzer (1949). These data were collected under sea-level conditions (1013 millibars and 20 degrees C).
Diameter (mm) Fall speed (m/s) Diameter (mm) Fall speed (m/s)
0.1 0.27 2.6 7.57
0.2 0.72 2.8 7.82
0.3 1.17 3.0 8.06
0.4 1.62 3.2 8.26
0.5 2.06 3.4 8.44
0.6 2.47 3.6 8.60
0.7 2.87 3.8 8.72
0.8 3.27 4.0 8.83
0.9 3.67 4.2 8.92
1.0 4.03 4.4 8.98
1.2 4.64 4.6 9.03
1.4 5.17 4.8 9.07
1.6 5.65 5.0 9.09
1.8 6.09 5.2 9.12
2.0 6.49 5.4 9.14
2.2 6.90 5.6 9.16
2.4 7.27 5.8 9.17
http://www.madsci.org/posts/archives/2000-07/962626446.Ph.r.html
***
Here's what I read last night while studying something else:
http://hypertextbook.com/facts/JianHuang.shtml
On snippet in there puts the average raindrop at 25 fps, or 7.62 meters/second. According to the earlier observations at sea level, that would correspond to a drop size between 2.6 and 2.8 mm.
So, the answer all "depends"...
Re: Judging wind speed by observing rain
yea with more research I would be inclined to go with a drop size of about 2-3 mm
anything bigger then 4mm supposedly splits into smaller drops (most of the time)
and for what its worth...drizzle has a fall speed of about 2 m/sec
I still think the answer is have a good spotter and watch the trail
yea with more research I would be inclined to go with a drop size of about 2-3 mm
anything bigger then 4mm supposedly splits into smaller drops (most of the time)
and for what its worth...drizzle has a fall speed of about 2 m/sec
I still think the answer is have a good spotter and watch the trail
Re: Judging wind speed by observing rain
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: hopps</div><div class="ubbcode-body">[snipped some good data and observations]
I still think the answer is have a good spotter and watch the trail </div></div>
Ah, but isn't the point to be able to observe conditions and dial in corrections so all the spotter gets to see is trace to the on-target hit, *instead of* reading mils of correction for the 2nd shot that you may never have a chance to take?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: hopps</div><div class="ubbcode-body">[snipped some good data and observations]
I still think the answer is have a good spotter and watch the trail </div></div>
Ah, but isn't the point to be able to observe conditions and dial in corrections so all the spotter gets to see is trace to the on-target hit, *instead of* reading mils of correction for the 2nd shot that you may never have a chance to take?
Re: Judging wind speed by observing rain
If you're out in the weather, why not use the Beaufort Wind Force Scale? Not accurate enough?
If you're out in the weather, why not use the Beaufort Wind Force Scale? Not accurate enough?
Re: Judging wind speed by observing rain
yep,..use the rain indication ( when constant) exactly as per those nice wind flag charts,..works well and actually pretty spot on.
yep,..use the rain indication ( when constant) exactly as per those nice wind flag charts,..works well and actually pretty spot on.
