All about forecasts
Short version: wind data is updated every 6 hours in FairWinds at 00:00, 06:00, 12:00, and 18:00 UTC (zulu time).
Currents are updated usually 1x or 2x a day depending on the resolution
1. Wind data
You can keep track of the active and upcoming forecasts on https://fairwinds.world/wind
FairWinds uses GFS 0p25 (0.25 degree) wind data, available from NOAA. GFS is a global, free weather data set. THe wind data is extracted from the 10-meter u and v vectors in the grib files. Grib files are a binary format file used to compress dense gridded data.
What most people think of as a global continuious field of forecast data is actually not how the data is created and released. Instead, think of the forecast as a series of data photographs stacked on each other, taken every 3 hours. These photos are called 'steps' and for a single forecast, NOAA releases them one at a time as soon as they are ready.
For example, take the 00:00 UTC forecast. NOAA starts crunching data at 00z, but it takes a while. They don't actually finish the first step until about 03:30. They then start uploading these steps to a public cloud.
They look like this
gfs.t00z.pgrb2.0p25.f000 27-Jan-2026 03:29 481M
gfs.t00z.pgrb2.0p25.f001 27-Jan-2026 03:29 509M
gfs.t00z.pgrb2.0p25.f002 27-Jan-2026 03:30 511M
gfs.t00z.pgrb2.0p25.f003 27-Jan-2026 03:30 511M
gfs.t00z.pgrb2.0p25.f004 27-Jan-2026 03:30 514M
gfs.t00z.pgrb2.0p25.f005 27-Jan-2026 03:31 514M
gfs.t00z.pgrb2.0p25.f006 27-Jan-2026 03:31 514M
gfs.t00z.pgrb2.0p25.f007 27-Jan-2026 03:31 513M
gfs.t00z.pgrb2.0p25.f008 27-Jan-2026 03:31 514M
....
So what you are looking at above is the first 8 hours of data 'snapshots'.
2. FairWinds forecast update schedule
Why are steps important?
FairWinds updates the wind data in the simulator and the race viewer every 6 hours using the previous cycle's forecast data.
The scheudle looks like this
| GFS Forecast Cycle | FairWinds Active Time (UTC) | Forecast Steps | Coverage |
|---|---|---|---|
| 00Z | 06:00 - 11:59 | f006-f012 | 6 hours |
| 06Z | 12:00 - 17:59 | f006- f012 | 6 hours |
| 12Z | 18:00 - 23:59 | f006-f012 | 6 hours |
| 18Z | 00:00 - 05:59 (next day) | f006-f012 | 6 hours |
3. Understanding wind changes
Since the simulator loads new forecasts every 6 hours it means you need to stay on top of the new wind in order to keep your boat heading in the right direction.
Because FairWinds loads a new wind data set every six hours, that means the forecast WILL change. And the wind you see in 24 hours will likely be different.