Winds Aloft Forecast

Private Pilot License (PPL) Notes

This section covers understanding wind, its effects on flight operations, and how to interpret winds aloft forecasts using both textual and graphical resources.

Understanding Wind and Its Effects:

1. Definition of Wind:
   1. Air in motion relative to the Earth's surface.
2. Effects on Airplane Performance:
   1. Affects every flight, from takeoff to landing.
   2. Determines runway selection for takeoff and landing.
   3. Strong winds may cause flight postponement or cancellation.
   4. Wind speed and direction can change with altitude.

Surface Wind Information:

1. Sources for Surface Wind Data:
   1. Text-based METAR reports.
   2. Automated systems like ASOS and AWOS.
2. Characteristics:
   1. Reports are generated from mechanical sensors on the ground.
   2. Provide accurate wind speed and direction information.

Winds Aloft Data:

1. Data Collection Methods:
   1. National Weather Service launches weather balloons daily.
   2. Balloons measure conditions from the surface to above 60,000 feet.
   3. Raw data is processed by computers with other inputs to predict wind speed and direction aloft.
   4. Data is also gathered from aircraft via GPS-derived winds.
2. Availability to Pilots:
   1. Available in both text-based and graphical forms.
   2. Graphical versions offer superior visualization and detail.
3. Advantages of Graphical Forecasts:
   1. View forecasts for nearly any point, separated by as little as 9 miles.
   2. Updated every hour on the Aviation Weather Center site.
   3. Visualize big-picture trends at various altitudes.
   4. Identify favorable routing, potential turbulence, and pressure systems.

Wind Direction References:

1. Winds Aloft Presentation:
   1. Presented relative to True North.
   2. Same for METARs and TAFs (if it's in print, it's true).
2. Surface Wind Reports:
   1. ATC reports, PIREPs, AWOS, ASOS, and ATIS provide winds relative to Magnetic North.
   2. Runway numbers, compasses, and heading indicators reference Magnetic North.

Interpreting Text-Based Winds Aloft Forecasts:

1. Understanding the Code:
   1. Wind direction: First two digits (in tens of degrees from which the wind is blowing).
   2. Wind speed: Next two digits (in knots).
   3. Temperature: Last two digits (degrees Celsius, preceded by a plus or minus sign).
2. Examples:
   1. At Louisville (LOU), 3,000 ft winds are from 230° at 25 knots.
   2. At 6,000 ft, winds are from 250° at 33 knots with a temperature of 6°C.
3. Additional Notes:
   1. No temperatures are forecast for the 3,000 ft level.
   2. Above 24,000 ft, minus sign is omitted as temperatures are assumed negative.
   3. Winds less than 1,500 ft above the surface are considered surface winds and not displayed.
   4. Code '9900' indicates light and variable winds less than 5 knots.

Accessing Winds Aloft Data:

1. Using Aviation Weather Center Website:
   1. Graphical Forecasts for Aviation (GFA):
      1. Select 'Winds' from the Weather menu.
      2. Wind barbs show speed and direction across the country.
      3. Color shading represents wind speed.
      4. Use altitude slider to adjust the displayed data to your cruising altitude.
      5. Use time slider to view forecasts up to 18 hours ahead.
      6. Utilize 'Flight Path' function to enter your route for specific forecasts.
   2. Viewing Temperature Forecasts:
      1. Select 'Temperature' from the Weather menu.
      2. Color shading represents temperatures at selected altitudes.
   3. Viewing Textual Winds Aloft Forecasts:
      1. Select 'Wind/Temp data' from the Products menu.
      2. Choose the forecast region, period, and level.
      3. Load data to view winds and temperatures aloft for reporting sites.
2. Using ForeFlight Application:
   1. Accessing Graphical Winds Aloft:
      1. Select 'Maps' screen.
      2. Choose 'Winds Aloft' layer from map options.
      3. Wind barbs are displayed; tap for exact wind speed, direction, and temperature.
      4. Adjust altitude slider for relevant data.
   2. Viewing Textual Winds Aloft Forecasts:
      1. Select an airport from the map.
      2. Tap the 'Weather' tab, then 'Winds' tab.
      3. ForeFlight decodes and presents data in an easy-to-read format.

Understanding and utilizing winds aloft forecasts are essential for flight planning, allowing pilots to anticipate wind conditions at various altitudes and make informed decisions for safe and efficient flights.