Windy & co. for spotters: forecasting wind, clouds and runway direction

The alarm is set for five, the camera is packed, and only at the fence do you notice: the wind shifted overnight, and all the landings come from the other side. This is exactly what a good weather map like Windy can usually reveal the evening before. You see which direction the surface wind blows from at the airport, how strong it is, whether the clouds hang low or just drift through as a thin veil – and whether the models even agree. This guide shows you which layers and settings matter for spotters, how to derive the runway direction in use from them and where the limits of every forecast lie.

Weather maps for spotters: the short answer

With a weather map you forecast the runway direction in use by comparing the forecast surface wind at the airport with the orientation of the runways. Aircraft prefer to take off and land into the wind. If the wind tomorrow comes strongly from the west, aircraft on an east-west runway will very likely take off toward the west and approach from the east. The cloud levels also tell you whether to expect sun, diffuse light or a gray sky.

Windy is the best-known tool for this, but not the only one. The principle works with any map that displays model data for wind, gusts and clouds hourly or every three hours. You need three things: the right altitude level, an understanding of how wind directions are stated, and the habit of looking at more than one model.

What Windy actually is

Windy is a weather platform from Prague that was founded in 2014 by Ivo Lukačovič and was originally called Windyty. The idea was an animated wind map; it has since grown into a comprehensive service that you use in the browser and as an app for iOS and Android. Windy doesn’t run the classic weather models itself, but displays the results of various weather services side by side.

For spotters, these building blocks are the most interesting:

• Model selection: Global models such as ECMWF (European Centre for Medium-Range Weather Forecasts), GFS (US weather service NOAA) and ICON (German Weather Service) as well as regional models such as ICON-EU, ICON-D2 and AROME.
• Map layers: Wind, gusts, clouds with top and base, visibility, precipitation, thunderstorms, plus radar and satellite images.
• Altitude selection: From the surface up to cruising altitudes – according to the app description, up to about FL450.
• Airport info: By searching for the ICAO or IATA code you find airports with runway information, METAR and TAF.
• Webcams: A large collection of public webcams, including some with a view of airports or their surroundings.

The basic features are free. According to the App Store description, a Premium subscription offers, among other things, forecasts in hourly steps, more frequent model updates and longer radar and satellite loops. For most spotters the free version is enough, and day planning with three-hour steps is generally perfectly sufficient.

The right level: surface wind instead of wind aloft

The most common mistake on a first look at Windy: the map doesn’t show the altitude you need. In the altitude selection you can switch between the surface and various pressure levels. At a few kilometers of altitude, the wind often blows much stronger and from a different direction than on the ground. For the runway direction in use, though, only the wind near the ground counts, which weather services state by default at a height of ten meters.

Before every planning session, make sure of the following:

1. Wind layer selected
2. Altitude set to surface
3. Timeline moved to the time of your spot visit
4. Airport tapped to read direction and strength at that point

The gusts layer is also worthwhile. A mean wind of 10 knots with gusts up to 30 knots is something completely different at the spot than a steady 10 knots. Strong gusts mean bumpy approaches and sometimes go-arounds – good subjects for videos, as the article on filming crosswind landings shows, but also shaky telephoto shots.

From wind arrow to runway direction in use

Once you’ve read off the surface wind, you compare it with the runway axis. The runway number is the rounded magnetic heading divided by ten – runway 25 points roughly at 250 degrees. If the wind is roughly on that axis, aircraft take off and land into it. The detailed logic behind this, including a calculator for headwind and crosswind components, is in the guide Understanding runway direction at airports.

Three rules of thumb help in practice:

• Strong wind from one direction: The forecast is quite reliable. At 10 knots and more near the runway axis, aircraft almost always fly into that wind.
• Weak or shifting wind: Here it gets uncertain. Many airports keep their runway direction in use as long as the tailwind doesn’t exceed a small limit. At Frankfurt Airport that is up to 5 knots according to the city’s aircraft noise reports. In calm conditions the direction that applied before usually stays – or the airport’s preferred one.
• Wind across the runway: Then the small along-runway component decides. The direction can flip as soon as the wind shifts by just a few degrees.

An example: at the Zeppelinheim viewing platform in a westerly wind you see the landings on the southern runway 25L from very close. If the weather map for the next morning shows strong wind from the southwest to west, the trip is worth it. If an easterly wind of 12 knots is forecast there, the landings come from the other side – then you need a different plan.

Wind per map	East-west runway (e.g. 07/25, 08/26)	What you expect at the spot
West to southwest, more than 8 kt	Runway direction west very likely	Landings from the east, takeoffs toward the west
East to northeast, more than 8 kt	Runway direction east very likely	Landings from the west, takeoffs toward the east
Under 5 kt, variable	open, the previous direction often stays	Wait for the live map in the morning
North or south, across the runway	flips with small shifts	Plan a backup spot, crosswind shots possible

The thresholds in this table are guide values, not the rules of a particular airport. Noise abatement concepts can override the wind logic – Zurich Airport, for example, works with approach concepts that depend on the time of day.

Knots, km/h, m/s: converting units

Windy and other maps display wind speed in different units depending on the setting. In aviation, knots are the norm, and METAR and TAF use them too. If your map shows km/h, you can convert quickly here:

Reading clouds: light or gray?

For photos the sky is almost as important as the runway direction in use. Windy distinguishes several levels of clouds, and that very distinction makes the difference:

• Low clouds sit near the ground and reliably block the sun. A closed low deck means gray, flat light.
• Mid-level clouds dampen the light strongly but sometimes leave gaps.
• High clouds are often thin veils of ice crystals. They make the light softer but frequently still let through enough sun for clean side views.

A total cloud cover of 80 percent can therefore mean very different things. If those 80 percent consist of high veils, the day can turn out well photographically. If it is a low stratus deck, probably not. How to take good pictures under a gray sky anyway is described in the article Plane spotting in bad weather.

The cloud base layer shows you how high the underside of the clouds is. If it hangs very low, approaches emerge from the cloud late, and you have only a short time for a picture. Together with the visibility layer you can also recognize fog situations in which low-visibility procedures apply at the airport and operations run more slowly.

Comparing weather models

Every weather map shows the output of a computational model. These models differ in resolution, run frequency and forecast range – and sometimes clearly in the result.

Model	Origin	Typical strength	Useful for spotters
ECMWF	European Centre for Medium-Range Weather Forecasts	global medium range, about 9 km grid	Planning several days ahead
GFS	US weather service NOAA	global coverage, frequent time steps	Cross-check to ECMWF
ICON / ICON-EU	German Weather Service	global or European coverage	Central Europe, two to four days ahead
ICON-D2	German Weather Service	about 2 km grid for Germany, Switzerland and Austria, recomputed several times a day	Fine planning for tomorrow
AROME	Météo-France	very fine grid for parts of Western Europe	Fine planning where available

High-resolution regional models depict terrain, coasts and local effects more precisely. According to the German Weather Service, ICON-D2 computes with a grid spacing of about 2.1 kilometers and is restarted eight times a day, but only reaches 27 hours into the future. Global models are coarser but reach further.

In Windy you switch the model via the model selection and so click through the forecasts one after another. It’s more convenient with the model comparison, which shows several forecasts for one location directly one below the other; the app description lists it among the Premium features. The rule of thumb: If the models agree, the forecast is reliable. If ECMWF shows westerly wind for Saturday morning and GFS easterly wind, the runway direction in use is open – then plan a spot that works in both directions, or decide again in the morning.

Other weather maps and tools

Windy has no monopoly. Depending on taste and purpose, other services come into question:

• Ventusky and Meteoblue also display model data as maps, with their own focuses in presentation and location forecasts.
• The German Weather Service offers radar, warnings and location forecasts. In thunderstorm situations, the precipitation radar is the best tool for the next few hours.
• METAR and TAF are the official aviation weather reports and forecasts for an airport. They are shorter and terser than any map but relate directly to the airfield. How to read them is explained in the guide Reading METAR and TAF.

You’ll find an overview of weather apps with strengths and weaknesses in the article Weather apps for spotters. What matters is less the tool than the routine: read off surface wind, gusts, cloud levels and visibility for the airport – and cross-check with current reports on the day itself.

Your workflow: from the evening before to the fence

With a bit of routine, weather planning for a spotting day takes only a few minutes. Here is how to proceed:

For step 5, the flight tracker app comparison has the right live maps. The approaches of the last half hour tell you the current runway direction in use more reliably than any forecast.

At Hamburg Airport, with its two crossing runways 05/23 and 15/33, this cross-check is especially important: depending on the wind, a different runway is used. From the Affenfelsen you look at 15/33 – whether anything is going on there depends strongly on the wind situation. At Munich Airport with its east-west parallel runway system, too, the wind direction decides whether takeoffs or landings pass you at the visitors’ hill (Besucherhügel).

What to watch out for

• A forecast is not a measurement. A model map shows what is likely. On the day itself, METAR and what the aircraft actually do count.
• Mind the time zones. Weather reports like METAR and TAF use Coordinated Universal Time (UTC). Check whether your map shows local time or UTC, otherwise in summer time (in Central Europe) you’ll be two hours off.
• Don’t underestimate local effects. Sea breezes at coastal airports, valley winds in the Alps or fog in river lowlands are often depicted only imprecisely by coarse models. High-resolution models and experience help here.
• Take thunderstorms seriously. If the map shows thunderstorms or high instability, keep an eye on the radar and leave the open fence area in good time. A telephoto lens on a tripod is no good companion in a lightning strike.
• Noise abatement beats wind. At some airports, fixed runway use applies at night or at certain times. The weather map knows nothing about that.

Conclusion

Weather maps like Windy take a large part of the luck out of a spotting day. If you read off the surface wind at the airport, compare the direction of origin with the runway axis and distinguish the clouds by level, you usually already know the evening before which spot will work. The model comparison shows you how certain the forecast is, and METAR plus the live map confirm in the morning what is really happening. With this routine you’ll stand at the wrong end of the runway far less often.