Winds Aloft & Weather Balloons

The Winds and Temperatures Aloft Forecast

Air masses are always on the move; changing direction and speed as they swirl around the globe. The movement of air across the earth’s surface is what we usually call wind.

Wind and temperature data from all levels of the atmosphere are necessary to create accurate forecast models. Meteorologists use model data to create the Winds and Temperatures Aloft Forecast. Pilots and dispatchers use the forecast to make accurate flight plans that optimize speed and fuel economy.

Scientists have made atmospheric observations for centuries. The first attempts at making upper-atmosphere measurements took place in the 1700s.

1930s Winds Aloft Reporting

As more airplanes took to the skies in the 1930s, accurate upper air data became a priority. In 1937, the US Weather Bureau (now the National Weather Service) created a network of stations that launched balloons with crude transmitters (radiosondes) to help meteorologists create winds aloft models. The work was tedious. Meteorologists collected and assembled the data by hand.

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Today’s Atmospheric Data Collection

The old radiosonde network remains active. The NWS now launches balloons from 92 location across the US and its territories. Worldwide, over 900 stations launch radiosondes twice a day. During unusual or severe weather, stations often make additional launches. That’s a lot of weather balloons!

Most launch stations fill the balloons with hydrogen (helium is expensive and in short supply). Radiosondes are lightweight packages that transmit pressure, temperature, humidity, and GPS position.

Weather service personnel launch balloons at least twice a day, at 0000z and 1200z (Coordinated Universal Time). A radiosonde transmits data every second as it ascends at 1000 feet/minute. After climbing to altitudes as high as 115,000 feet, the balloon bursts and the radiosonde package descends safely with a small parachute.

Man holding a 6 foot diameter white balloon. His assistant holding the small white cardboard box radiosonde. Preparing to release the balloon.
Yellowstone National Park meteorologists launch a weather balloon with radiosonde to help predict local weather and fire behavior. National Park Service Photo

Watch a Balloon Launch!

The video was shot September 13, 2012, as Meteorology students from Mississippi State University fill and launch a weather balloon near Starkville. NWS Memphis representatives were in attendance to watch.

MSU has a Severe Weather Launch program that allows students to launch radiosondes on severe weather days to provide supplemental data to the NOAA/National Weather Service Storm Prediction Center.

Things to watch for:

  • The guy handling the balloon makes a considerable effort not to touch the latex. Oils from human skin will cause the balloon to burst prematurely.
  • After release, the team confirms they are receiving radiosonde data. The antenna and receiver can be seen next to the laptop.
Video provided by Meteorologist Ryan Hoke @RyanHokeWAVE3

How is radiosonde data used?

Researchers and meteorologists use balloon soundings for :

  • Weather prediction models
  • Local severe storm forecasting
  • Aviation, fire weather, and marine forecasts
  • Weather and climate change research
  • Input for air pollution models

Weather Balloon Trivia

• Why use weather balloons? No other data collection system can match the accuracy, sample rate, and height coverage obtained by radiosondes lofted by balloons.

• Weather balloons are made of a biodegradable latex. The balloons shatter into small pieces at high altitudes. Recovery parachutes and string are also biodegradable to minimize environmental impact.

• About 20% of the 75,000 radiosondes launched by the NWS each year are found and returned. The equipment is refurbished and reused. If you find a radiosonde, you can return it to the NWS for free.

• The FAA must be informed of weather balloon launches within 5 miles of a controlled airport. Weather balloons present little risk to aircraft.

• The 1967 British sci-fi series “The Prisoner,” used a weather balloon for the role of “Rover,” a creepy white bubble that maintains discipline in The Village.

Rover from 1967’s “The Prisoner”

The Winds and Temps Aloft Forecast

Forecasters generate the aviation Winds and Temperatures Aloft Forecast using models made with the help of balloon radiosonde data. The forecast is issued four times a day and includes data that is valid for 6, 12, and 24 hours. Wind and temperature data are included for altitudes of 3, 6, 9, 12, 18, 24, 30, 34, and 39 thousand feet.

The US National Weather Service Aviation Weather Center provides the forecast in several formats. The most basic product is a tabular list of locations with wind direction, speed, and temperature at the different altitudes. The format is perfect if you’re curious about the winds and temperatures for a few locations.

Before computers, internet, and remote terminals, pilots would telephone a Flight Service Station to receive winds and temperatures aloft. The briefer would read the data for each station along the route of flight. The pilot calculated headings and ground speeds by hand. [Narrator: “It was not a pleasant task.”]

Wind aloft data. Each row of data consists of a 3 letter identifier for location,  then wind direction, speed and temperature for each altitude.
Winds aloft data for the north central US.
You can see live forecast data at aviationweather.gov

Winds Aloft Visualizations

A picture is worth 1000 words. A quick glance at tabular data doesn’t provide a “big picture” of what’s going on in the atmosphere; especially for a long route.

Wind Barbs

Sailors and meteorologists came up with an easy way to visualize winds. Weather services standardized wind symbols in the 1940s, but the concept hasn’t changed since the 1800s.

weather map from eighteen eighty eight showing pressure lines (isobars) and wind arrows.
March 12 surface analysis of Great Blizzard of 1888. Arrows point the direction of flow, feathers depict speed, circles indicate weather at the station. Source: NOAA

In the early days, forecasters drew the “wind barbs” on weather maps by hand. Now, the data is pulled from servers and automatically depicted. A quick glance at the screenshot below gives you an idea of forecast air mass movement and speed at 34,000 feet.

Screen shot of NWS Aviation Weather page. Central US with wind barbs or arrows spread over map showing direction of upper air movement.
28 April 2020 Winds & Temps Aloft 0000 UTC forecast. AviationWeather.gov

Think of wind barbs like an arrow with a point and feathers. The pointy end points the direction of the air mass flow. The feathers, or barbs, depict the wind speed. Winds aloft charts often display the temperature (in Celsius) next to each barb. Wind speed is easy to decipher…

  • Short barbs = 5 knots
  • Long barbs = 10 knots
  • Pennants = 50 knots
Decoding Winds Aloft Chart. Same information in article text.

Flight Planning Software

Global weather providers, including the National Weather Service, provide winds aloft data in machine readable formats. Airlines and general aviation pilots use flight planning software that can use the wind data to generate very accurate flight plans optimized for speed and/or fuel savings.

Foreflight planning app shows a planned flight with time en route and fuel burn for each altitude in 2000 foot increments.1000 feet to 12,000 feet.
The ForeFlight planning app pulls wind data from the NWS server and GFS prediction model to provide pilots with accurate altitude-based time and fuel burn options.

Jeppesen FliteDeck Pro X, a popular app with airlines, can display winds aloft barbs with the route of flight. This feature helps flight crews understand why dispatchers may have created a route that seems out-of-the way. The wind barbs also help pilots anticipate wind shifts and turbulence along the route.

Check out the two routes from Louisville to Anchorage in the following image. The straight line indicates the great circle route (shortest distance) and is 2713 nautical miles.

Our dispatcher generated a route that took us farther north, adding 114 nm to the journey. The longer route avoided a 140 knot headwind saving us considerable time and fuel.

map of North America with wind barbs showing the jet stream coming down from Canada. Direct route from Louisville to Anchorage flies right into the jet stream. Alternate route avoids the jet stream.
Compare the direct route with a longer route optimized for winds aloft.
Screenshot from Jeppesen FliteDeck Pro X

Check out the low pressure area in the center of the screen shot below. The wind barbs clearly depict the counter-clockwise movement of the air mass. The “feathers” of the wind barbs always point inward toward the center of the low pressure area.

Map of Pacific ocean showing wind barbs in a circular pattern indicating a low pressure area.
Forecast winds aloft at FL340 over the Pacific. Screenshot from Jeppesen FliteDeck Pro X

Windy Animation

Wind barbs are nice, but Windy.com improves the concept. Windy uses the machine readable model data to provide a stunning animation of air mass movement.

Windy allows the user to zoom to any area of the earth and select altitude, forecast time, and forecast model. The video below is centered on the same low pressure area as the image above. You can really see the counter-clockwise circulation.

I use Windy.com as part of my weather review before every long flight.

Animated air mass movement from Windy.com. Wind speeds are color coded.

More About Winds

If you’d like to read more about the effect of winds on aircraft, check out Headwinds and Tailwinds.

13 Comments

  1. Really fascinating stuff, Ken. I actually came upon a launched and landed radiosonde by my home once. It was put up by NWS KSGF during a storm, and ended up at my place over 125 miles away!! Wonder what the record distance is. Thanks for this!

    • That is SO cool. I’d love to find one. Did you find the pre-paid mailer hiding inside so you could return it?

      Thanks for reading!

  2. Captain Hoke, as I have come to expect your information is extreme interesting and informative. On a different note I would like to tell you that I have been using flight sim-ware for many years. In your honor, I have purchased a Boeing 767 freighter in UPS livery and started making sim flights with it. Meet you in the simulated skies!!

    • Hi Steve, that’s really cool. A fun real-time route you can fly (and one of my favorites) is Kuala Lumpur (KUL/WMKK) to Penang (PEN/WMKP). It’s short and scenic. The view when approaching runway 04 is awesome.

      Happy Flying!
      Ken

      • I have SimBrief working on the routing right now. Will take the sim flight in the morning (east coast USA) I will tell the simulated airport officials @ WMKP that you sent me!!

  3. Hi Ken, Great post!! I remember a long time ago along with dispatch duty I was a weather observer. Our airport did not regularly launch weather balloons but the NWS required us to launch one occasionally I guess to stay current doing so? A couple times a year we would launch one as described in the story and it was kinda cool watching it climb away.

  4. Hello Ken, amazing article as always. could you also explain the low and high pressure effect on the plane? Thank you

    • Hi Ehsan,

      High and low pressure systems have some effect on takeoff performance – not dramatic unless a high altitude airport and high temps are involved. The biggest impact are the types of weather these systems bring with them. Low pressure: Cyclones (Hurricanes/Typhoons), stormy weather, winter weather. High pressure: calm winds, clear skies, haze, fog. These are generalizations – there are always exceptions.

  5. Hi Ken
    Really like this post. During our flight last Tuesday from SW Florida to Raleigh in our 172 we altitude deviated twice for headwinds. Saved at least an hour on our trip.

  6. Hello Ken!
    From Windy do you prefer a particular model?
    Personally I look at all 4 and come up with an “average”
    (ECMWF is usually closer to my average).

    • For what I use it for, the model doesn’t make much difference. Short term forecast, they’re pretty close. I just leave it on whatever the default model is.

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