For many hobbies and career fields, the speed and direction of the wind are vital information. Whether you are sailing a boat, windsurfing, piloting an aircraft, or participating in any number of outdoor activities, the reading of a map with the wind’s direction and speed on it can be critical. An anemometer is a tool that allows users to measure the speed and direction of the wind, though there are many different kinds! Read on to learn more about how wind speed and direction are measured, displayed in weather maps, and get answers to frequently asked questions.
Practical Uses of Wind Direction Indicators
Changes to wind speed and direction can be hard to predict and occur without much warning, so it is important for us to be aware of these fluctuations for a number of reasons. Meteorologists report wind speed and direction to help people better plan their days and prepare for hazardous weather. Utility companies measure wind speed and direction to anticipate fire risk, enabling them to turn off power to areas with wind speeds that could down powerlines. Surfers check wind conditions before they head into the water to identify the best surf spots, or avoid dangerous conditions.
There are many different tools and sensors that measure and record wind conditions, and not every kind is appropriate for your specific application. For example, a wind direction indicator sailboat’s responsibility varies from one used to measure this information for an aircraft. And while most people wouldn’t have much use for a large windsock in their backyard, they would likely benefit from a home weather station with a sonic anemometer in it so that they know the wind conditions at their location.
Measuring Wind Speed & Direction
Sonic and mechanical sensors measure the wind in different ways. Mechanical sensors use moving parts and are connected to a data logger or other data recording device. The “cups” for speed and “vane” for direction change measurement physically move with changes in the wind and give accurate readings of speed and direction.
- Sonic Wind Sensor Used in the Tempest Weather System, a sonic anemometer uses sonic pulses to detect air movement. Sonic (or ultrasonic) sensors operate without moving parts. On a typical sonic anemometer, a transducer sends a pulse of ultrasonic sound from the north-facing side of the sensor. A microprocessor measures the time it takes to travel to the south transducer. The wind speed is calculated from the time it takes the ultrasound to travel to the opposite transducer. Measurement times are affected by the wind speed and direction blowing along the line between the transducers.
- Cup Anemometers Originally created with four cups, the cup anemometer (also known as a rotational anemometer) consists of hemispherical cups mounted on horizontal arms, fixed on a vertical shaft. The air flows turn the cups at a rate that is approximately proportional to the wind speed. Thus, counting the turns of the shaft over a set time interval produces a value proportional to the average wind speed for a wide range of speeds.
- Weathervane Often seen on top of barns, weathervanes come in a variety of shapes and styles. The classic style features a spinning arrow situated above four horizontal posts that read “N,” “S,” “E,” and “W” (north, south, east, and west) to help the viewer determine the wind direction. Reading a weathervane is easy. Whichever direction the arrow is pointing will indicate where the wind is coming from.
- Wind Sock (AKA Wind Cone) You may have noticed this type of wind vane near the runway at the airports as you landed or took off. While a wind sock determines wind direction, it generally does not indicate a north/south/east/west direction. Based on how much the sock inflates, the viewer can estimate the strength of the wind. This is particularly useful for pilots, as they need to account for the wind to help when landing or taking off.
- Handheld Anemometer Handheld wind and weather meters are portable wind measurement devices that features a propeller wind sensor, where the impeller spins and we correlate the number of rotations to a wind speed through our calibration curve. From a technical point of view, the anemometer can read speeds up to 125 mph, with + or – 0.5% accuracy. If you like to camp, hike, sail, or hunt, these kinds of portable meters are a handy tool to have.
Wind Direction Indicators on Maps
On weather maps, wind speed and direction are often displayed with wind barbs (4). Wind barbs have three components: a dot, a staff and feathers or flags. The staff part of a wind barb shows wind direction, while the dot end of the staff indicates where the wind is blowing to, and the top of the staff shows the direction from which the wind is coming. Wind speed is indicated by feathers (short lines) added to the top of the staff. These feathers show wind speed rounded to the nearest 5 mph increment. When winds are 2 mph or less, a small open circle is used. A short feather represents a 5 mph average wind speed, while a long feather equals 10 mph. A pennant or flag is used to show a 50-mph wind speed.
Wind direction indicators may also be displayed more simply on weather maps, with arrows pointing in the direction from which the wind is coming from, alongside the wind speed measured that that location. For example, the iWindsurf app displays wind on maps like this:
DIY Wind Vanes
Do-it-yourself (DIY) wind vanes can be a fun option for for a weather-related project, and makes a great learning activity for kids, families, or anyone with an interest in measuring the wind and weather. DIY wind vanes can be purchased as a sophisticated pre-made kit or by using simple materials you might already have in your home. While it won’t be as accurate as a commercial or consumer wind vane, making one yourself is a great way to begin taking wind direction measurements. Learn how you can make your own wind vane with paper plates, poster board, modeling clay, and a few other materials (4).
Wind Measurement: FAQs
- How can you tell wind direction?
- What is wind direction?
One of the most fundamental points to remember when it comes to translating wind speed and direction data is that the direction of the wind is always the direction FROM which the wind blows and NOT the direction toward which the wind blows. This means that you can tell the wind direction by reading where the wind is coming from to determine where it is going. It can be helpful to recognize this when dealing with certain maps, aircraft, and boats in everyday career fields (sometimes also used with weather trackers and stations).
Wind direction is commonly known as the direction that the wind is blowing, and we use this to understand the more technical parts of its definition. It is grouped into an average of eight basic directions (i.e. N, NE, E, SE, etc.) which split into sixteen more specific directions (i.e. NNE, ESE, SSE, etc.) which can then become even more precise when locating the degree of the direction of the wind (i.e. 90 degrees–exactly due East, 180 degrees–exactly due South, etc.). The varying specificity of these directions allows for several jobs to be done at the precision at which they require, whether it be foundational understanding of the directions or highly specific needs to be met.