Long-range aviation weather forecasts have become more and more accurate over the years. These forecasts are generally created three to five days ahead of day-of-flight operation. Specific weather modeling computer programs – when interpreted by experienced aviation weather professionals – provide business aircraft operators with valuable tools in the preliminary trip and permit planning process.

The following is an overview of what you need to know:

1. Long-range forecasts have advantages

Long-range forecasts benefit operators in many ways. Preliminary forecasts provide a snapshot of high-level en-route conditions – including frontal systems, jet stream activity, and expected turbulence. These preliminary insights can help provide a route plot, based on expected weather, to give the operator visual reference of en-route conditions, together with forecasts for departure/arrival locations and alternate airports. Long-range forecasts, which can be either written or oral, assist operators in determining best routing, preferred alternates, and overflight permit requirements when change of route is needed.

2. Forecasts help fine-tune overflight permit requirements

Good long-range forecasts can be invaluable in determining needed overflight permits. For example, if you’re flying from Anchorage (PANC) to Japan, you may or may not require a Russian overflight permit – depending on predicted upper-level winds, temperature, and unusual weather activity. If best wind conditions are over Russian airspace, you’ll want to know this in advance in order to secure permits within required lead times. It’s also important to be aware of significant weather events such as typhoons which may impact route of flight and alternates. There have been numerous situations in which a typhoon could impact weather in areas with limited high-altitude routes.

3. Long-range forecasts offer other benefits

Having an accurate long-range forecast enables operators to shorten flight routing, avoid areas of turbulence, and limit exposure to adverse weather conditions. Knowing upper wind and general weather conditions assists in determining best route, turbulence avoidance, technical stops, and required fuel load. Long-range forecasts also reveal extensive weather problems that may exist in the arrival region – such as widespread fog or low ceilings. Many passengers today are highly turbulence-sensitive. Information about turbulence aloft allows the captain to be aware of a region with high-shear values and offers the opportunity to make route changes to avoid such areas.

4. Long-range forecasts are now more accurate

Compared to 10-15 years ago – thanks to improved forecasting tools – today’s long-range forecasts are more accurate. A long-range forecast – three to five days out – can be done for any region of the world. However, these forecasts are not as accurate more than five days in advance because weather parameters can change. Forecasts are typically most accurate for inter-tropical convergence zones (monsoon troughs) as it’s possible to better predict daily weather activity. This is because regions of convective activity cover large areas, creating similar weather patterns on a constant basis.

5. There are different types of long-range forecasts

Long-range forecasts are available under different parameters, to suit individual operator needs/requests. Common requests may focus on winds aloft or jet stream activity, surface winds and fog, or volcanic ash conditions. Correlation of winds and temperature aloft are commonly requested in order to estimate more accurate fuel burns. Although there’s a high degree of variability in what an operator may need from a long-range forecast, all of this information is readily available from your 3rd-party provider.

6. Forecasting technology continues to improve

In the past there was greater need to extrapolate long-range weather data, but today’s computer weather models are more intuitive. Global Forecasting System medium-long range high-resolution models (HIRES AVN MODEL) are the preferred technology as they provide maximum weather insight for aviation purposes. Medium long-range forecasts cover anything from the next day to seven days out. High-resolution weather models are programmed to calculate longer-range weather patterns with maximum accuracy. It’s important to note, however, that computer weather models are not as accurate over large areas of water or expanses of desert due to lack of available data inputs.

7. Always use experienced aviation weather providers

With so many variables impacting accuracy of long-range forecasts, it’s important to use an experienced 3rd-party provider. Depending on where you’re flying, your 3rd-party provider may need to extrapolate weather data – particularly when destination airports lack availability of terminal area forecasts. Experienced providers have the ability to give operators better and more accurate estimates in terms of surface winds and expected turbulence.

8. 24-, 36-, 48-, and 72-hour forecasts

Many operators like to view general weather trends seven days out, but the best weather predictions are usually 24-48 hours ahead of the estimated time of departure. Computer models typically break weather conditions down to three-hour periods. In terms of winds aloft, it’s best to look at the mid-point of a trip to get the most accurate/relevant information. Winds aloft predictions typically will not change much over a 24-30-hour window. You’ll want to consider predicted 700-500 millibar and flight level 180-200 conditions to get the best prediction of likely conditions at destination airports. These parameters allow operators to determine moisture at different levels. The information can then be translated to determine local conditions at the destination airport.

9. The human element remains important

Accuracy of a long-range weather forecast depends on interpretation of the weather model and all available information. The human element remains an important part of the process. Online and/or canned weather programs do not provide the same level of long-range weather insight.

Closing thoughts

While five-seven day weather outlooks are beneficial in terms of route and permit planning, it’s best to also consider a long-range forecast of three days or less ahead of operation to confirm expected conditions. At 24 hours out, it’s recommended to re-confirm predicted wind conditions and international standard atmosphere – and fine-tune flight plan/routing – with latest weather and weather modeling information.

Questions?

If you have any questions about this article, contact me at davehoule@univ-wea.com.