Wind speed and weather always correlate. One of the main tasks of a weather station is to keep an eye on the wind speed and send out warnings when this speed hits critical levels.
They do it with an anemometer, a device made for the very purpose of measuring wind speed. Even a half-century back, our grandparents could’ve guessed wind speed through intuition and experience.
But, We don’t always have an anemometer thats why we need to learn how to measure wind speed without an anemometer. Most of us, if not all, don’t even have a clue to begin with. What’ll happen if your trusty old anemometer gives out on you? Unless you’re a weather-freak, you won’t have a portable weather station with you all the time.
Not trying to sound like the back-to-tradition slogan, but wouldn’t it be great if you knew how to get an accurate-enough assumption the old way? Well, if you’re here, it seems we agree.
Benefits of Measuring Wind Speed
Why do we measure wind velocity? In short, we do it to understand and prepare for the upcoming weather. The benefits are vital.
Wind speeds can tell you a lot about the weather and how it’s going to turn out at the end of the day. Yes, wind speed is a fundamental factor in forecasting the weather correctly. Wind speed alone can help you forecast the next 7 days, granted that it won’t be 100% accurate.
You can determine whether it’s a cold front that is approaching or a warm front. And prep accordingly.
It’s a part of weather forecasting, but it’s a more real-time update to the overall condition of the sky. The rate of velocity increase in the air is a tell-tale sign of storms forming on the horizon.
You must have heard the terms tornado watch and tornado warning in the Weather TV report. It’s the wind speed that helps the meteorologists give out warning signals.
Preparation for Heavy Rainfall
Floods are almost always associated with cyclones and other low-pressure systems. Even heavy rainfall during the monsoon always poses a risk of flooding.
And just like any other component of the weather, wind speed has something to do with it.
Related: Top US rainiest cities list.
Plot the Atmospheric Pressure
Wind speed can tell you if it’s a low-pressure system or a high-pressure one. A low-pressure system moves at double the speed of a high-pressure system.
If you plot wind speeds at many different points, it’ll give you a pattern. The wind speeds in this pattern will tell you how much further the points are from the center of the storm.
Also read: Atmospheric and Barometric pressure details.
3 Ways to Measure Wind Speed without an Anemometer?
An anemometer tells you the wind speed as a hard fact. It's digital. Without an anemometer, you can't get an exact idea, but analog systems can be extremely helpful in most situations. And there are quite a few “analog” ways to explore. Let’s dig in.
Windsocks, aka wind cones, are a popular way of measuring wind speed in both offshore and onshore conditions. You may have seen it used in airports. It’s a cheap way of doing it, but a helpful one nonetheless.
The good news is that industrial-grade windsocks are calibrated with the help of an anemometer by the manufacturers. So, even if you don’t have an anemometer, you still have the chance to get an accurate reading.
The white and orange stripes were initially used to help estimate the velocity. Each stripe added 3 knots (3.45 mph). When the sock is fully extended, it’d mean the velocity is 15 knots (17 mph) or greater.
One caution: Some ring-frame mountings cause the windsocks to always have an open-end which indicates 3 knots velocity, but you should know that it’s not the case.
Remember that the above measurements are calibrated for a windsock with the following dimensions and configuration,
ICAO/UK CAA Standard:
Size: 12ft/3.60 m in length and 36-inch/0.9m in throat diameter
Height: 20ft/6m mast height
#1 8ft/2.5m in length and 18-inch/0.45m in throat diameter
#2 12ft/3.75m in length and 36-inch/0.9m in throat diameter
#1 FAA L-806 support: Maximum of 3m/10ft mast height if hoisted on a low-mass supporting structure
#2 FAA L-807 support: Maximum of 4.8m/16ft if hoisted on a rigid high-mass supporting structure
2. Homemade Anemometer by Using Cups
It might sound childish but hold your horses. A simple instrument made from 5 cups and a few straws can actually accomplish a lot. Here’s what you need to do,
Step 1 – Get the Tools
You’re going to need the following,
- Paper cups
- Pair of scissors
- Pencil with eraser
Step 2 – Make the Central Cup
Use the scissors to create holes in the walls of a cup. The holes should be evenly spaced and near the edge.
Step 3 – Insert Straws into the Base Cup
Now, grab 2 straws and insert them through the holes so that they overlap. It should look like an X.
Step 4 – Create the Stand
Take the central cup and make a hole at its base using a pencil. This pencil will be the stand. The eraser end of the pencil should be touching the section where the two straws overlapped.
Now, insert the pushpin at that overlapping point to hold them together.
Step 5 – Prepare the Outer Cups
Grab the scissors and 4 paper cups. Make holes in two opposite sides of the cups. The holes should be at the same distance from the edge.
Step 6 – Add the Outer Cups
It’s time to finish up. Take the outer cups and insert each end of the straws into each of the cups through their holes.
All of the cups should be facing the bottom of the cup in front of it.
Step 7 – Time to Measure
Now, you can start measuring the wind speed with the homemade instrument. Mark the bottom of one cup to help count the number of revolutions.
Note down the number of revolutions per minute. Usually, 10 revolutions in one minute correspond to 1mph wind velocity.
But I'd calibrate the readings using an anemometer. That way, you can accurately read wind speed later when you don't have one.
Calibration is simple. Measure the wind speed for a minute while counting the rev per minute. Take as many readings as possible and make a chart. This will be your guideline. Lots of observations will give you more accurate readings.
3. Using a Ribbon
The concept isn't something new. It's an old way of measurement still in use in many parts of the world. The less fortunate people of the third world, especially those who live on the outskirts of the modern world, still implement the idea.
It’s hard to get good at this since everything has to be guessed through long observation and experience.
Step 1 – Grab the Required Components
You’re going to need a ribbon, a stick, and tape to build the tool.
Step 2 – Attach the Ribbon and the Stick
Cut a few pieces from the ribbon and place them atop each other. On one end, tie them well. Take the tied end of the ribbons and tape it onto the stick.
Step 3 – Hold It Against the Wind
Grab the tool and go to an open space with enough wind blowing. Hold it up in the direction of the wind.
Take notes on how the ribbons behave with the wind. Things would be much better if you could calibrate the readings with an anemometer. Once you’re done with the calibration, you can use the non-digital methods to get an almost accurate wind speed measurement.
Calibrating a Wind Ribbon
Calibration is simple. When you have the ribbon up against the wind, it’ll move and stay at different angles at different speeds. What you need to do is note the angle of the ribbon against the stick and its corresponding wind speed from an anemometer.
Take as many readings as you can. Take the readings on different days and weeks. The more observations you make, the greater your chance of getting it right. It’s the golden rule of conducting experiments.
Now, draw X and Y axis on a piece of graph paper. Put the ribbon angle on the X-axis and the wind speed on the Y-axis. Plot the data from the readings you took, you should now have a curve.
This curve will be your guideline next time you’re measuring the wind speed. And you won’t need an anemometer.
Related: Weather vanes working principle described.
Tips to Determine Perfect Wind Speed
You can use all the tools in the world, but you still can get bad measurements. It has to do with the basics of measuring wind speeds. Ensure the following to do it right,
- Choose a place at least 100 feet away from obstructions, i.e., buildings and trees
- The spot has to be at the height of 30 feet or greater
- Calibrate the tool with a known accurate anemometer
- Don’t measure on only one day, rather spread the measurement in different days to measure wind speed in different weather conditions
- Use industry-grade tools instead of hand-made ones if you can’t calibrate
Frequently Asked Questions
1. What is the scale for wind speed?
The Beaufort scale is known to be the wind speed scale. It was Francis Beaufort who developed the scale back in 1805. The HMS Beagle of the royal navy first officially used the scale.
2. Do meteorologists use windsocks?
Yes, despite having complex machines and devices, meteorologists readily use windsocks to get observations about the wind speed and direction.
3. Where should a windsock be placed?
You should install a windsock in an open space. But the design of the windsock makes it more appropriate for use on runways, helipads, or in low light conditions.
The contrasting colors with fluorescents let people know about the wind condition during the night and prevent accidents.
4. Are anemometers reliable?
Anemometers are reliable as long as you keep them clean and do maintenance regularly. But a little change in ambient temperature can mess with the reading.
5. What is the issue with the hot wire anemometer?
Surrounding temperature easily affects the hot-wired anemometer. Temperature drifting causes most of its errors.
6. Are anemometers waterproof?
Most anemometers aren't waterproof, which makes them vulnerable to the weather, just like the primitive tools.
7. Do anemometers need calibration?
Of course, they need to be calibrated just like the alternatives mentioned above. In fact, to get accurate readings, you need to calibrate them multiple times a year.
I think we have established the need to know how to measure wind speed without an anemometer. No, you don’t need to reside in one of the third world countries to find a use for it.
Those simple methods could be the lifesaver you never expected it to be. But the vital point to note is that the people in the under-developed areas are experts at reading the wind speed just by looking at the ribbon. They don’t even need calibration.
So, I keep reminding you of the importance of getting used to using different instruments. Without keeping in touch, you won’t get the experience required to be proficient at them.