The verified forecast badge

A forecast is more useful when you know how far to trust it. Altiwind checks itself: it compares the last hours of forecast wind and gusts with what the nearest airport actually measured, picks the model that has been closest in your area and tells you how far off it has been running. The result is a small badge on your forecast, free for everyone.

How it works

1. Find the nearest airport. Altiwind looks for an airport within 25 km of your spot that publishes METAR weather reports, fetched from aviationweather.gov.
2. Look back 6–24 hours. It takes the reported wind and gusts over that stretch.
3. Compare 2–3 models. For the same hours and the same airport, it checks what each candidate model forecast.
4. Pick the best and show the bias. The model with the smallest error for that area is used, and the badge shows its bias: how much, on average, it has been running high or low.

Reading the badge

A badge might read:

Checked vs EGLL 40 min ago: running 3 km/h high

• EGLL is the airport's ICAO code, here London Heathrow.
• 40 min ago is how long ago the latest airport report was checked.
• Running 3 km/h high means the forecast wind has recently been about 3 km/h (1.9 mph, 1.6 kn) stronger than what the airport measured. The real wind may be a touch lighter than shown. "Running low" is the one to watch: the real wind has been stronger than forecast, so give yourself extra margin.

A small bias is a good sign. A large one, or a bias that flips between checks, tells you the weather is doing something the models are struggling with.

What it can't do

• It checks one station. One airport, one point. It says nothing about the far side of a hill.
• It checks 10 m only. Airport anemometers sit about 10 m above the ground. Doing well at 10 m is a good sign for the wind at altitude, but not proof.
• Airports are open sites. Flat ground, short grass, few obstacles. A field by a wood, a valley or a town centre can be more sheltered or gustier.
• The recent past isn't the future. When a front is passing, the last few hours' bias may not hold for the next few.
• No airport within 25 km, no badge. You still get the forecast from the regional model, just without the check.

Example

You're planning an afternoon flight on the edge of west London. The badge says "Checked vs EGLL 40 min ago: running 3 km/h high". The forecast shows 25 km/h at 120 m, with estimated gusts to 38 km/h. Knowing the model has been running slightly high, you can read that as a little under 25 km/h. Had the badge said "running 5 km/h low", you'd treat the same forecast as nearer 30 km/h and check your drone's margin again.

Is it free?

The verified badge is free, with no account.

To make sense of the airport reports themselves, read METAR for drone pilots. For how the different models compare, see weather models explained.